aboutsummaryrefslogtreecommitdiffstats
path: root/contrib/libs/protobuf/CHANGES.txt
blob: b7866d502b19d5b17143a1536bff47578e4628f9 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
1713
1714
1715
1716
1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
1749
1750
1751
1752
1753
1754
1755
1756
1757
1758
1759
1760
1761
1762
1763
1764
1765
1766
1767
1768
1769
1770
1771
1772
1773
1774
1775
1776
1777
1778
1779
1780
1781
1782
1783
1784
1785
1786
1787
1788
1789
1790
1791
1792
1793
1794
1795
1796
1797
1798
1799
1800
1801
1802
1803
1804
1805
1806
1807
1808
1809
1810
1811
1812
1813
1814
1815
1816
1817
1818
1819
1820
1821
1822
1823
1824
1825
1826
1827
1828
1829
1830
1831
1832
1833
1834
1835
1836
1837
1838
1839
1840
1841
1842
1843
1844
1845
1846
1847
1848
1849
1850
1851
1852
1853
1854
1855
1856
1857
1858
1859
1860
1861
1862
1863
1864
1865
1866
1867
1868
1869
1870
1871
1872
1873
1874
1875
1876
1877
1878
1879
1880
1881
1882
1883
1884
1885
1886
1887
1888
1889
1890
1891
1892
1893
1894
1895
1896
1897
1898
1899
1900
1901
1902
1903
1904
1905
1906
1907
1908
1909
1910
1911
1912
1913
1914
1915
1916
1917
1918
1919
1920
1921
1922
1923
1924
1925
1926
1927
1928
1929
1930
1931
1932
1933
1934
1935
1936
1937
1938
1939
1940
1941
1942
1943
1944
1945
1946
1947
1948
1949
1950
1951
1952
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
2024
2025
2026
2027
2028
2029
2030
2031
2032
2033
2034
2035
2036
2037
2038
2039
2040
2041
2042
2043
2044
2045
2046
2047
2048
2049
2050
2051
2052
2053
2054
2055
2056
2057
2058
2059
2060
2061
2062
2063
2064
2065
2066
2067
2068
2069
2070
2071
2072
2073
2074
2075
2076
2077
2078
2079
2080
2081
2082
2083
2084
2085
2086
2087
2088
2089
2090
2091
2092
2093
2094
2095
2096
2097
2098
2099
2100
2101
2102
2103
2104
2105
2106
2107
2108
2109
2110
2111
2112
2113
2114
2115
2116
2117
2118
2119
2120
2121
2122
2123
2124
2125
2126
2127
2128
2129
2130
2131
2132
2133
2134
2135
2136
2137
2138
2139
2140
2141
2142
2143
2144
2145
2146
2147
2148
2149
2150
2151
2152
2153
2154
2155
2156
2157
2158
2159
2160
2161
2162
2163
2164
2165
2166
2167
2168
2169
2170
2171
2172
2173
2174
2175
2176
2177
2178
2179
2180
2181
2182
2183
2184
2185
2186
2187
2188
2189
2190
2191
2192
2193
2194
2195
2196
2197
2198
2199
2200
2201
2202
2203
2204
2205
2206
2207
2208
2209
2210
2211
2212
2213
2214
2215
2216
2217
2218
2219
2220
2221
2222
2223
2224
2225
2226
2227
2228
2229
2230
2231
2232
2233
2234
2235
2236
2237
2238
2239
2240
2241
2242
2243
2244
2245
2246
2247
2248
2249
2250
2251
2252
2253
2254
2255
2256
2257
2258
2259
2260
2261
2262
2263
2264
2265
2266
2267
2268
2269
2270
2271
2272
2273
2274
2275
2276
2277
2278
2279
2280
2281
2282
2283
2284
2285
2286
2287
2288
2289
2290
2291
2292
2293
2294
2295
2296
2297
2298
2299
2300
2301
2302
2303
2304
2305
2306
2307
2308
2309
2310
2311
2312
2313
2314
2315
2316
2317
2318
2319
2320
2321
2322
2323
2324
2325
2326
2327
2328
2329
2330
2331
2332
2333
2334
2335
2336
2337
2338
2339
2340
2341
2342
2343
2344
2345
2346
2347
2348
2349
2350
2351
2352
2353
2354
2355
2356
2357
2358
2359
2360
2361
2362
2363
2364
2365
2366
2367
2368
2369
2370
2371
2372
2373
2374
2375
2376
2377
2378
2379
2380
2381
2382
2383
2384
2385
2386
2387
2388
2389
2390
2391
2392
2393
2394
2395
2396
2397
2398
2399
2400
2401
2402
2403
2404
2405
2406
2407
2408
2409
2410
2411
2412
2413
2414
2415
2416
2417
2418
2419
2420
2421
2422
2423
2424
2425
2426
2427
2428
2429
2430
2431
2432
2433
2434
2435
2436
2437
2438
2439
2440
2441
2442
2443
2444
2445
2446
2447
2448
2449
2450
2451
2452
2453
2454
2455
2456
2457
2458
2459
2460
2461
2462
2463
2464
2465
2466
2467
2468
2469
2470
2471
2472
2473
2474
2475
2476
2477
2478
2479
2480
2481
2482
2483
2484
2485
2486
2487
2488
2489
2490
2491
2492
2493
2494
2495
2496
2497
2498
2499
2500
2501
2502
2503
2504
2505
2506
2507
2508
2509
2510
2511
2512
2513
2514
2515
2516
2517
2518
2519
2520
2521
2522
2523
2524
2525
2526
2527
2528
2529
2530
2531
2532
2533
2534
2535
2536
2537
2538
2539
2540
2541
2542
2543
2544
2545
2546
2547
2548
2549
2550
2551
2552
2553
2554
2555
2556
2557
2558
2559
2560
2561
2562
2563
2564
2565
2566
2567
2568
2569
2570
2571
2572
2573
2574
2575
2576
2577
2578
2579
2580
2581
2582
2583
2584
2585
2586
2587
2588
2589
2590
2591
2592
2593
2594
2595
2596
2597
2598
2599
2600
2601
2602
2603
2604
2605
2606
2607
2608
2609
2610
2611
2612
2613
2614
2615
2616
2617
2618
2619
2620
2621
2622
2623
2624
2625
2626
2627
2628
2629
2630
2631
2632
2633
2634
2635
2636
2637
2638
2639
2640
2641
2642
2643
2644
2645
2646
2647
2648
2649
2650
2651
2652
2653
2654
2655
2656
2657
2658
2659
2660
2661
2662
2663
2664
2665
2666
2667
2668
2669
2670
2671
2672
2673
2674
2675
2676
2677
2678
2679
2680
2681
2682
2683
2684
2685
2686
2687
2688
2689
2690
2691
2692
2693
2694
2695
2696
2697
2698
2699
2700
2701
2702
2703
2704
2705
2706
2707
2708
2709
2710
2711
2712
2713
2714
2715
2716
2717
2718
2719
2720
2721
2722
2723
2724
2725
2726
2727
2728
2729
2730
2731
2732
2733
2734
2735
2736
2737
2738
2739
2740
2741
2742
2743
2744
2745
2746
2747
2748
2749
2750
2751
2752
2753
2754
2755
2756
2757
2758
2759
2760
2761
2762
2763
2764
2765
2766
2767
2768
2769
2770
2771
2772
2773
2774
2775
2776
2777
2778
2779
2780
2781
2782
2783
2784
2785
2786
2787
2788
2789
2790
2791
2792
2793
2794
2795
2796
2797
2798
2799
2800
2801
2802
2803
2804
2805
2806
2807
2808
2809
2810
2811
2812
2813
2814
2815
2816
2817
2818
2819
2820
2821
2822
2823
2824
2825
2826
2827
2828
2829
2830
2831
2832
2833
2834
2835
2836
2837
2838
2839
2840
2841
2842
2843
2844
2845
2846
2847
2848
2849
2850
2851
2852
2853
2854
2855
2856
2857
2858
2859
2860
2861
2862
2863
2864
2865
2866
2867
2868
2869
2870
2871
2872
2873
2874
2875
2876
2877
2878
2879
2880
2881
2882
2883
2884
2885
2886
2887
2888
2889
2890
2891
2892
2893
2894
2895
2896
2897
2898
2899
2900
2901
2902
2903
2904
2905
2906
2907
2908
2909
2910
2911
2912
2913
2914
2915
2916
2917
2918
2919
2920
2921
2922
2923
2924
2925
2926
2927
2928
2929
2930
2931
2932
2933
2934
2935
2936
2937
2938
2939
2940
2941
2942
2943
2944
2945
2946
2947
2948
2949
2950
2951
2952
2953
2954
2955
2956
2957
2958
2959
2960
2022-09-13 version 18.3 (C++/Java/Python/PHP/Objective-C/C#/Ruby)


2022-01-05 version 3.18.2 (C++/Java/Python/PHP/Objective-C/C#/Ruby/JavaScript)

  Java
  * Improve performance characteristics of UnknownFieldSet parsing (#9371) 

2021-10-04 version 3.18.1 (C++/Java/Python/PHP/Objective-C/C#/Ruby/JavaScript)

  Python
  * Update setup.py to reflect that we now require at least Python 3.5 (#8989)
  * Performance fix for DynamicMessage: force GetRaw() to be inlined (#9023)

  Ruby
  * Update ruby_generator.cc to allow proto2 imports in proto3 (#9003)

2021-09-13 version 3.18.0 (C++/Java/Python/PHP/Objective-C/C#/Ruby/JavaScript)

  C++
  * Fix warnings raised by clang 11 (#8664)
  * Make StringPiece constructible from std::string_view (#8707)
  * Add missing capability attributes for LLVM 12 (#8714)
  * Stop using std::iterator (deprecated in C++17). (#8741)
  * Move field_access_listener from libprotobuf-lite to libprotobuf (#8775)
  * Fix #7047 Safely handle setlocale (#8735)
  * Remove deprecated version of SetTotalBytesLimit() (#8794)
  * Support arena allocation of google::protobuf::AnyMetadata (#8758)
  * Fix undefined symbol error around SharedCtor() (#8827)
  * Fix default value of enum(int) in json_util with proto2 (#8835)
  * Better Smaller ByteSizeLong
  * Introduce event filters for inject_field_listener_events
  * Reduce memory usage of DescriptorPool
  * For lazy fields copy serialized form when allowed.
  * Re-introduce the InlinedStringField class
  * v2 access listener
  * Reduce padding in the proto's ExtensionRegistry map.
  * GetExtension performance optimizations
  * Make tracker a static variable rather than call static functions
  * Support extensions in field access listener
  * Annotate MergeFrom for field access listener
  * Fix incomplete types for field access listener
  * Add map_entry/new_map_entry to SpecificField in MessageDifferencer. They
    record the map items which are different in MessageDifferencer's reporter.
  * Reduce binary size due to fieldless proto messages
  * TextFormat: ParseInfoTree supports getting field end location in addition to
    start.
  * Fix repeated enum extension size in field listener
  * Enable Any Text Expansion for Descriptors::DebugString()
  * Switch from int{8,16,32,64} to int{8,16,32,64}_t

  Java
  * Fix errorprone conflict (#8723)
  * Removing deprecated TimeUtil class. (#8749)
  * Optimized FieldDescriptor.valueOf() to avoid array copying.
  * Removing deprecated TimeUtil class.
  * Add Durations.parseUnchecked(String) and Timestamps.parseUnchecked(String)
  * FieldMaskUtil: Add convenience method to mask the fields out of a given proto.

  JavaScript
  * Optimize binary parsing of repeated float64
  * Fix for optimization when reading doubles from binary wire format
  * Replace toArray implementation with toJSON.

  Python
  * Drops support for 2.7 and 3.5.

  PHP
  * Migrate PHP & Ruby to ABSL wyhash (#8854)
  * Added support for PHP 8.1 (currently in RC1) to the C extension (#8964)
  * Fixed PHP SEGV when constructing messages from a destructor. (#8969)

  Ruby
  * Move DSL implementation from C to pure Ruby (#8850)
  * Fixed a memory bug with RepeatedField#+. (#8970)

  Other
  * [csharp] ByteString.CreateCodedInput should use ArraySegment offset and count (#8740)
  * [ObjC] Add support for using the proto package to prefix symbols. (#8760)
  * field_presence.md: fix Go example (#8788)


2021-06-04 version 3.17.3 (C++/Java/Python/PHP/Objective-C/C#/Ruby/JavaScript)
  C++
  * Introduce FieldAccessListener.
  * Stop emitting boilerplate {Copy/Merge}From in each ProtoBuf class
  * Fixed some uninitialized variable warnings in generated_message_reflection.cc.

  Kotlin
  * Fix duplicate proto files error (#8699)

  Java
  * Fixed parser to check that we are at a proper limit when a sub-message has
    finished parsing.

2021-05-25 version 3.17.2 (C++/Java/Python/PHP/Objective-C/C#/Ruby/JavaScript)
  Kotlin
  * Fix duplicate class error (#8653)

  PHP
  * Fixed SEGV in sub-message getters for well-known types when message is unset
    (#8670)

2021-05-07 version 3.17.1 (C++/Java/Python/PHP/Objective-C/C#/Ruby/JavaScript)
  PHP
  * Fixed PHP memory leaks and arginfo errors. (#8614)
  * Fixed JSON parser to allow multiple values from the same oneof as long as
    all but one are null.

  Ruby
  * Fixed memory bug: properly root repeated/map field when assigning. (#8639)
  * Fixed JSON parser to allow multiple values from the same oneof as long as
    all but one are null.


2021-05-07 version 3.17.0 (C++/Java/Python/PHP/Objective-C/C#/Ruby/JavaScript)

  Protocol Compiler
  * Fix the generated source information for reserved values in Enums.

  C++
  * Fix -Wunused-parameter in map<string, int> fields (fixes #8494) (#8500)
  * Use byteswap.h when building against musl libc (#8503)
  * Fix -Wundefined-inline error when using SharedCtor() or SharedDtor() (#8532)
  * Fix bug where `Descriptor::DebugString()` printed proto3 synthetic oneofs.
  * Provide stable versions of `SortAndUnique()`.
  * Make sure to cache proto3 optional message fields when they are cleared.
  * Expose UnsafeArena methods to Reflection.
  * Use std::string::empty() rather than std::string::size() > 0.

  Kotlin
  * Restrict extension setter and getter operators to non-nullable T.

  Java
  * updating GSON and Guava to more recent versions (#8524)
  * Reduce the time spent evaluating isExtensionNumber by storing the extension
    ranges in a TreeMap for faster queries. This is particularly relevant for
    protos which define a large number of extension ranges, for example when
    each tag is defined as an extension.
  * Fix java bytecode estimation logic for optional fields.
  * Optimize Descriptor.isExtensionNumber.

  Python
  * Add MethodDescriptor.CopyToProto() (#8327)
  * Remove unused python_protobuf.{cc,h} (#8513)
  * Start publishing python aarch64 manylinux wheels normally (#8530)
  * Fix constness issue detected by MSVC standard conforming mode (#8568)
  * Make JSON parsing match C++ and Java when multiple fields from the same
    oneof are present and all but one is null.

  Ruby
  * Add support for proto3 json_name in compiler and field definitions (#8356)
  * Fixed memory leak of Ruby arena objects. (#8461)
  * Fix source gem compilation (#8471)
  * Fix various exceptions in Ruby on 64-bit Windows (#8563)
  * Fix crash when calculating Message hash values on 64-bit Windows (#8565)

  Conformance Tests
  * Added a conformance test for the case of multiple fields from the same
    oneof.

2021-04-06 version 3.16.0 (C++/Java/Python/PHP/Objective-C/C#/Ruby/JavaScript)
  Other
  * Opensourcing kotlin protos (#8272)
  * Use a newer version of rules_proto, with the new rule `proto_descriptor_set` (#8469)

  C++
  * Fix compiler warnings issue found in conformance_test_runner #8189 (#8190)
  * Fix MinGW-w64 build issues. (#8286)
  * [Protoc] C++ Resolved an issue where NO_DESTROY and CONSTINIT are in incorrect order (#8296)
  * Fix PROTOBUF_CONSTINIT macro redefinition (#8323)
  * Delete StringPiecePod (#8353)
  * Fix gcc error: comparison of unsigned expression in '>= 0' is always … (#8309)
  * Fix cmake install on iOS (#8301)
  * Create a CMake option to control whether or not RTTI is enabled (#8347)
  * Fix endian.h location on FreeBSD (#8351)
  * Refactor util::Status (#8354)
  * Make util::Status more similar to absl::Status (#8405)
  * Fix -Wsuggest-destructor-override for generated C++ proto classes. (#8408)
  * Refactor StatusOr and StringPiece (#8406)
  * Refactor uint128 (#8416)
  * The ::pb namespace is no longer exposed due to conflicts.
  * Allow MessageDifferencer::TreatAsSet() (and friends) to override previous
    calls instead of crashing.
  * Reduce the size of generated proto headers for protos with `string` or
    `bytes` fields.
  * Move arena() operation on uncommon path to out-of-line routine
  * For iterator-pair function parameter types, take both iterators by value.
  * Code-space savings and perhaps some modest performance improvements in
    RepeatedPtrField.
  * Eliminate nullptr check from every tag parse.
  * Remove unused _$name$_cached_byte_size_ fields.
  * Serialize extension ranges together when not broken by a proto field in the
    middle.
  * Do out-of-line allocation and deallocation of string object in ArenaString.
  * Streamline ParseContext::ParseMessage<T> to avoid code bloat and improve
    performance.
  * New member functions RepeatedField::Assign, RepeatedPtrField::{Add, Assign}.
  * Fix undefined behavior warning due to innocuous uninitialization of value
    on an error path.
  * Avoid expensive inlined code space for encoding message length for messages
    >= 128 bytes and instead do a procedure call to a shared out-of-line routine.
  * util::DefaultFieldComparator will be final in a future version of protobuf.
    Subclasses should inherit from SimpleFieldComparator instead.

  C#
  * Add .NET 5 target and improve WriteString performance with SIMD (#8147)

  Java
  * deps: update JUnit and Truth (#8319)
  * Detect invalid overflow of byteLimit and return InvalidProtocolBufferException as documented.
  * Exceptions thrown while reading from an InputStream in parseFrom are now
    included as causes.
  * Support potentially more efficient proto parsing from RopeByteStrings.
  * Clarify runtime of ByteString.Output.toStringBuffer().
  * Added UnsafeByteOperations to protobuf-lite (#8426)

  JavaScript
  * Make Any.pack() chainable.

  Python
  * Fix some constness / char literal issues being found by MSVC standard conforming mode (#8344)
  * Switch on "new" buffer API (#8339)
  * Enable crosscompiling aarch64 python wheels under dockcross manylinux docker image (#8280)
  * Fixed a bug in text format where a trailing colon was printed for repeated field.
  * When TextFormat encounters a duplicate message map key, replace the current
    one instead of merging.

  Objective-C
  * Move the class map to a CFDictionary. (#8328)

  PHP
  * read_property() handler is not supposed to return NULL (#8362)
  * Changed parameter type from long to integer (#7613)
  * fix: README supported PHP version for C extension (#8236)

  Ruby
  * Fixed quadratic memory usage when appending to arrays. (#8364)
  * Fixed memory leak of Ruby arena objects. (#8461)
  * Add support for proto3 json_name in compiler and field definitions. (#8356)

  Other
  * Some doc on AOT compilation and protobuf (#8294)
  * [CMake] Ability to pass options to protoc executable from cmake (#8374)
  * Add --fatal_warnings flag to treat warnings as errors (#8131)
  * [bazel] Remove deprecated way to depend on googletest (#8396)
  * add error returns missing from protoc to prevent it from exiting with… (#8409)


2021-04-07 version 3.15.8 (C++/Java/Python/PHP/Objective-C/C#/Ruby/JavaScript)

  Ruby
  * Fixed memory leak of Ruby arena objects (#8461)

2021-04-02 version 3.15.7 (C++/Java/Python/PHP/Objective-C/C#/Ruby/JavaScript)

  C++
  * Remove the ::pb namespace (alias) (#8423)

  Ruby
  * Fix unbounded memory growth for Ruby <2.7 (#8429)
  * Fixed message equality in cases where the message type is different (#8434)

2021-03-10 version 3.15.6 (C++/Java/Python/PHP/Objective-C/C#/Ruby/JavaScript)

  Ruby
  * Fixed bug in string comparison logic (#8386)

2021-03-04 version 3.15.5 (C++/Java/Python/PHP/Objective-C/C#/Ruby/JavaScript)

  Ruby
  * Fixed quadratic memory use in array append (#8379)

  PHP
  * Fixed quadratic memory use in array append (#8379)

  C++
  * Do not disable RTTI by default in the CMake build (#8377)

2021-03-02 version 3.15.4 (C++/Java/Python/PHP/Objective-C/C#/Ruby/JavaScript)

  Ruby
  * Fixed SEGV when users pass nil messages (#8363)
  * Fixed quadratic memory usage when appending to arrays (#8364)

  C++
  * Create a CMake option to control whether or not RTTI is enabled (#8361)

  PHP
  * read_property() handler is not supposed to return NULL (#8362)

2021-02-25 version 3.15.3 (C++/Java/Python/PHP/Objective-C/C#/Ruby/JavaScript)

  Ruby
  * Ruby <2.7 now uses WeakMap too, which prevents memory leaks. (#8341)

2021-02-23 version 3.15.2 (C++/Java/Python/PHP/Objective-C/C#/Ruby/JavaScript)

  Ruby
  * Fix for FieldDescriptor.get(msg) (#8330)

  C++
  * Fix PROTOBUF_CONSTINIT macro redefinition (#8323)

2021-02-05 version 3.15.1 (C++/Java/Python/PHP/Objective-C/C#/Ruby/JavaScript)

  Ruby
  * Bugfix for Message.[] for repeated or map fields (#8313)

2021-02-05 version 3.15.0 (C++/Java/Python/PHP/Objective-C/C#/Ruby/JavaScript)

  Protocol Compiler
  * Optional fields for proto3 are enabled by default, and no longer require
    the --experimental_allow_proto3_optional flag.

  C++
  * MessageDifferencer: fixed bug when using custom ignore with multiple
    unknown fields
  * Use init_seg in MSVC to push initialization to an earlier phase.
  * Runtime no longer triggers -Wsign-compare warnings.
  * Fixed -Wtautological-constant-out-of-range-compare warning.
  * DynamicCastToGenerated works for nullptr input for even if RTTI is disabled
  * Arena is refactored and optimized.
  * Clarified/specified that the exact value of Arena::SpaceAllocated() is an
    implementation detail users must not rely on. It should not be used in
    unit tests.
  * Change the signature of Any::PackFrom() to return false on error.
  * Add fast reflection getter API for strings.
  * Constant initialize the global message instances
  * Avoid potential for missed wakeup in UnknownFieldSet
  * Now Proto3 Oneof fields have "has" methods for checking their presence in
    C++.
  * Bugfix for NVCC
  * Return early in _InternalSerialize for empty maps.
  * Adding functionality for outputting map key values in proto path logging
    output (does not affect comparison logic) and stop printing 'value' in the
    path. The modified print functionality is in the
    MessageDifferencer::StreamReporter.
  * Fixed https://github.com/protocolbuffers/protobuf/issues/8129
  * Ensure that null char symbol, package and file names do not result in a
    crash.
  * Constant initialize the global message instances
  * Pretty print 'max' instead of numeric values in reserved ranges.
  * Removed remaining instances of std::is_pod, which is deprecated in C++20.
  * Changes to reduce code size for unknown field handling by making uncommon
    cases out of line.
  * Fix std::is_pod deprecated in C++20 (#7180)
  * Fix some -Wunused-parameter warnings (#8053)
  * Fix detecting file as directory on zOS issue #8051 (#8052)
  * Don't include sys/param.h for _BYTE_ORDER (#8106)
  * remove CMAKE_THREAD_LIBS_INIT from pkgconfig CFLAGS (#8154)
  * Fix TextFormatMapTest.DynamicMessage issue#5136 (#8159)
  * Fix for compiler warning issue#8145 (#8160)
  * fix: support deprecated enums for GCC < 6 (#8164)
  * Fix some warning when compiling with Visual Studio 2019 on x64 target (#8125)

  Python
  * Provided an override for the reverse() method that will reverse the internal
    collection directly instead of using the other methods of the BaseContainer.
  * MessageFactory.CreateProtoype can be overridden to customize class creation.
  * Fix PyUnknownFields memory leak (#7928)
  * Add macOS Big Sur compatibility (#8126)

  JavaScript
  * Generate `getDescriptor` methods with `*` as their `this` type.
  * Enforce `let/const` for generated messages.
  * js/binary/utils.js: Fix jspb.utils.joinUnsignedDecimalString to work with negative bitsLow and low but non-zero bitsHigh parameter. (#8170)

  PHP
  * Added support for PHP 8. (#8105)
  * unregister INI entries and fix invalid read on shutdown (#8042)
  * Fix PhpDoc comments for message accessors to include "|null". (#8136)
  * fix: convert native PHP floats to single precision (#8187)
  * Fixed PHP to support field numbers >=2**28. (#8235)
  * feat: add support for deprecated fields to PHP compiler (#8223)
  * Protect against stack overflow if the user derives from Message. (#8248)
  * Fixed clone for Message, RepeatedField, and MapField. (#8245)
  * Updated upb to allow nonzero offset minutes in JSON timestamps. (#8258)

  Ruby
  * Added support for Ruby 3. (#8184)
  * Rewrote the data storage layer to be based on upb_msg objects from the
    upb library. This should lead to much better parsing performance,
    particularly for large messages. (#8184).
  * Fill out JRuby support (#7923)
  * [Ruby] Fix: (SIGSEGV) gRPC-Ruby issue on Windows. memory alloc infinite
    recursion/run out of memory (#8195)
  * Fix jruby support to handle messages nested more than 1 level deep (#8194)

  Java
  * Avoid possible UnsupportedOperationException when using CodedInputSteam
    with a direct ByteBuffer.
  * Make Durations.comparator() and Timestamps.comparator() Serializable.
  * Add more detailed error information for dynamic message field type
    validation failure
  * Removed declarations of functions declared in java_names.h from
    java_helpers.h.
  * Now Proto3 Oneof fields have "has" methods for checking their presence in
    Java.
  * Annotates Java proto generated *_FIELD_NUMBER constants.
  * Add -assumevalues to remove JvmMemoryAccessor on Android.

  C#
  * Fix parsing negative Int32Value that crosses segment boundary (#8035)
  * Change ByteString to use memory and support unsafe create without copy (#7645)
  * Optimize MapField serialization by removing MessageAdapter (#8143)
  * Allow FileDescriptors to be parsed with extension registries (#8220)
  * Optimize writing small strings (#8149)

2020-11-11 version 3.14.0 (C++/Java/Python/PHP/Objective-C/C#/Ruby/JavaScript)

  Protocol Compiler
  * The proto compiler no longer requires a .proto filename when it is not
    generating code.
  * Added flag `--deterministic_output` to `protoc --encode=...`.
  * Fixed deadlock when using google.protobuf.Any embedded in aggregate options.

  C++
  * Arenas are now unconditionally enabled. cc_enable_arenas no longer has
    any effect.
  * Removed inlined string support, which is incompatible with arenas.
  * Fix a memory corruption bug in reflection when mixing optional and
    non-optional fields.
  * Make SpaceUsed() calculation more thorough for map fields.
  * Add stack overflow protection for text format with unknown field values.
  * FieldPath::FollowAll() now returns a bool to signal if an out-of-bounds
    error was encountered.
  * Performance improvements for Map.
  * Minor formatting fix when dumping a descriptor to .proto format with
    DebugString.
  * UBSAN fix in RepeatedField (#2073).
  * When running under ASAN, skip a test that makes huge allocations.
  * Fixed a crash that could happen when creating more than 256 extensions in
    a single message.
  * Fix a crash in BuildFile when passing in invalid descriptor proto.
  * Parser security fix when operating with CodedInputStream.
  * Warn against the use of AllowUnknownExtension.
  * Migrated to C++11 for-range loops instead of index-based loops where
    possible. This fixes a lot of warnings when compiling with -Wsign-compare.
  * Fix segment fault for proto3 optional (#7805)
  * Adds a CMake option to build `libprotoc` separately (#7949)

  Java
  * Bugfix in mergeFrom() when a oneof has multiple message fields.
  * Fix RopeByteString.RopeInputStream.read() returning -1 when told to read
    0 bytes when not at EOF.
  * Redefine remove(Object) on primitive repeated field Lists to avoid
    autoboxing.
  * Support "\u" escapes in textformat string literals.
  * Trailing empty spaces are no longer ignored for FieldMask.
  * Fix FieldMaskUtil.subtract to recursively remove mask.
  * Mark enums with `@java.lang.Deprecated` if the proto enum has option
    `deprecated = true;`.
  * Adding forgotten duration.proto to the lite library (#7738)

  Python
  * Print google.protobuf.NullValue as null instead of "NULL_VALUE" when it is
    used outside WKT Value/Struct.
  * Fix bug occurring when attempting to deep copy an enum type in python 3.
  * Add a setuptools extension for generating Python protobufs (#7783)
  * Remove uses of pkg_resources in non-namespace packages. (#7902)
  * [bazel/py] Omit google/__init__.py from the Protobuf runtime. (#7908)
  * Removed the unnecessary setuptools package dependency for Python package (#7511)
  * Fix PyUnknownFields memory leak (#7928)

  PHP
  * Added support for "==" to the PHP C extension (#7883)
  * Added `==` operators for Map and Array. (#7900)
  * Native C well-known types (#7944)
  * Optimized away hex2bin() call in generated code (#8006)
  * New version of upb, and a new hash function wyhash in third_party. (#8000)
  * add missing hasOneof method to check presence of oneof fields (#8003)

  Go:
  * Update go_package options to reference google.golang.org/protobuf module.

  C#:
  * annotate ByteString.CopyFrom(ReadOnlySpan<byte>) as SecuritySafeCritical (#7701)
  * Fix C# optional field reflection when there are regular fields too (#7705)
  * Fix parsing negative Int32Value that crosses segment boundary (#8035)

  Javascript:
  * JS: parse (un)packed fields conditionally (#7379)

2020-07-14 version 3.13.0 (C++/Java/Python/PHP/Objective-C/C#/Ruby/JavaScript)

  PHP:
  * The C extension is completely rewritten. The new C extension has significantly
    better parsing performance and fixes a handful of conformance issues. It will
    also make it easier to add support for more features like proto2 and proto3 presence.
  * The new C extension does not support PHP 5.x. PHP 5.x users can still use pure-PHP.

  C++:
  * Removed deprecated unsafe arena string accessors
  * Enabled heterogeneous lookup for std::string keys in maps.
  * Removed implicit conversion from StringPiece to std::string
  * Fix use-after-destroy bug when the Map is allocated in the arena.
  * Improved the randomness of map ordering
  * Added stack overflow protection for text format with unknown fields
  * Use std::hash for proto maps to help with portability.
  * Added more Windows macros to proto whitelist.
  * Arena constructors for map entry messages are now marked "explicit"
    (for regular messages they were already explicit).
  * Fix subtle aliasing bug in RepeatedField::Add
  * Fix mismatch between MapEntry ByteSize and Serialize with respect to unset
    fields.

  Python:
  * JSON format conformance fixes:
    * Reject lowercase t for Timestamp json format.
    * Print full_name directly for extensions (no camelCase).
    * Reject boolean values for integer fields.
    * Reject NaN, Infinity, -Infinity that is not quoted.
    * Base64 fixes for bytes fields: accept URL-safe base64 and missing padding.
  * Bugfix for fields/files named "async" or "await".
  * Improved the error message when AttributeError is returned from __getattr__
    in EnumTypeWrapper.

  Java:
  * Fixed a bug where setting optional proto3 enums with setFooValue() would
    not mark the value as present.
  * Add Subtract function to FieldMaskUtil.

  C#:
  * Dropped support for netstandard1.0 (replaced by support for netstandard1.1).
    This was required to modernize the parsing stack to use the `Span<byte>`
    type internally. (#7351)
  * Add `ParseFrom(ReadOnlySequence<byte>)` method to enable GC friendly
    parsing with reduced allocations and buffer copies. (#7351)
  * Add support for serialization directly to a `IBufferWriter<byte>` or
    to a `Span<byte>` to enable GC friendly serialization.
    The new API is available as extension methods on the `IMessage` type. (#7576)
  * Add `GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE` define to make
    generated code compatible with old C# compilers (pre-roslyn compilers
    from .NET framework and old versions of mono) that do not support
    ref structs. Users that are still on a legacy stack that does
    not support C# 7.2 compiler might need to use the new define
    in their projects to be able to build the newly generated code. (#7490)
  * Due to the major overhaul of parsing and serialization internals (#7351 and #7576),
    it is recommended to regenerate your generated code to achieve the best
    performance (the legacy generated code will still work, but might incur
    a slight performance penalty).

2020-07-28 version 3.12.4 (C++/Java/Python/PHP/Objective-C/C#/Ruby/JavaScript)

This release contains no significant changes, but exists because 3.12.3 was
mistakenly tagged at the wrong commit.

2020-06-01 version 3.12.3 (C++/Java/Python/PHP/Objective-C/C#/Ruby/JavaScript)

  Objective-C
  * Tweak the union used for Extensions to support old generated code. #7573

2020-05-26 version 3.12.2 (C++/Java/Python/PHP/Objective-C/C#/Ruby/JavaScript)

  C++
  * Simplified the template export macros to fix the build for mingw32. (#7539)

  Objective-C
  * Fix for the :protobuf_objc target in the Bazel BUILD file. (#7538)

2020-05-20 version 3.12.1 (C++/Java/Python/PHP/Objective-C/C#/Ruby/JavaScript)

  Ruby
  * Re-add binary gems for Ruby 2.3 and 2.4. These are EOL upstream, however
    many people still use them and dropping support will require more
    coordination.

2020-05-12 version 3.12.0 (C++/Java/Python/PHP/Objective-C/C#/Ruby/JavaScript)

  Protocol Compiler
  * [experimental] Singular, non-message typed fields in proto3 now support
    presence tracking. This is enabled by adding the "optional" field label and
    passing the --experimental_allow_proto3_optional flag to protoc.
    * For usage info, see docs/field_presence.md.
    * During this experimental phase, code generators should update to support
      proto3 presence, see docs/implementing_proto3_presence.md for instructions.
  * Allow duplicate symbol names when multiple descriptor sets are passed on
    the command-line, to match the behavior when multiple .proto files are passed.
  * Deterministic `protoc --descriptor_set_out` (#7175)

  C++
  * [experimental] Added proto3 presence support.
  * New descriptor APIs to support proto3 presence.
  * Enable Arenas by default on all .proto files.
  * Documented that users are not allowed to subclass Message or MessageLite.
  * Mark generated classes as final; inheriting from protos is strongly discouraged.
  * Add stack overflow protection for text format with unknown fields.
  * Add accessors for map key and value FieldDescriptors.
  * Add FieldMaskUtil::FromFieldNumbers().
  * MessageDifferencer: use ParsePartial() on Any fields so the diff does not
    fail when there are missing required fields.
  * ReflectionOps::Merge(): lookup messages in the right factory, if it can.
  * Added Descriptor::WellKnownTypes enum and Descriptor::well_known_type()
    accessor as an easier way of determining if a message is a Well-Known Type.
  * Optimized RepeatedField::Add() when it is used in a loop.
  * Made proto move/swap more efficient.
  * De-virtualize the GetArena() method in MessageLite.
  * Improves performance of json_stream_parser.cc by factor 1000 (#7230)
  * bug: #7076 undefine Windows OUT and OPTIONAL macros (#7087)
  * Fixed a bug in FieldDescriptor::DebugString() that would erroneously print
    an "optional" label for a field in a oneof.
  * Fix bug in parsing bool extensions that assumed they are always 1 byte.
  * Fix off-by-one error in FieldOptions::ByteSize() when extensions are present.
  * Clarified the comments to show an example of the difference between
    Descriptor::extension and DescriptorPool::FindAllExtensions.
  * Add a compiler option 'code_size' to force optimize_for=code_size on all
    protos where this is possible.

  Java
  * [experimental] Added proto3 presence support.
  * Mark java enum _VALUE constants as @Deprecated if the enum field is deprecated
  * reduce <clinit> size for enums with allow_alias set to true.
  * Sort map fields alphabetically by the field's key when printing textproto.
  * Fixed a bug in map sorting that appeared in -rc1 and -rc2 (#7508).
  * TextFormat.merge() handles Any as top level type.
  * Throw a descriptive IllegalArgumentException when calling
    getValueDescriptor() on enum special value UNRECOGNIZED instead of
    ArrayIndexOutOfBoundsException.
  * Fixed an issue with JsonFormat.printer() where setting printingEnumsAsInts()
    would override the configuration passed into includingDefaultValueFields().
  * Implement overrides of indexOf() and contains() on primitive lists returned
    for repeated fields to avoid autoboxing the list contents.
  * Add overload to FieldMaskUtil.fromStringList that accepts a descriptor.
  * [bazel] Move Java runtime/toolchains into //java (#7190)

  Python
  * [experimental] Added proto3 presence support.
  * [experimental] fast import protobuf module, only works with cpp generated code linked in.
  * Truncate 'float' fields to 4 bytes of precision in setters for pure-Python
    implementation (C++ extension was already doing this).
  * Fixed a memory leak in C++ bindings.
  * Added a deprecation warning when code tries to create Descriptor objects
    directly.
  * Fix unintended comparison between bytes and string in descriptor.py.
  * Avoid printing excess digits for float fields in TextFormat.
  * Remove Python 2.5 syntax compatibility from the proto compiler generated _pb2.py module code.
  * Drop 3.3, 3.4 and use single version docker images for all python tests (#7396)

  JavaScript
  * Fix js message pivot selection (#6813)

  PHP
  * Persistent Descriptor Pool (#6899)
  * Implement lazy loading of php class for proto messages (#6911)
  * Correct @return in Any.unpack docblock (#7089)
  * Ignore unknown enum value when ignore_unknown specified (#7455)

  Ruby
  * [experimental] Implemented proto3 presence for Ruby. (#7406)
  * Stop building binary gems for ruby <2.5 (#7453)
  * Fix for wrappers with a zero value (#7195)
  * Fix for JSON serialization of 0/empty-valued wrapper types (#7198)
  * Call "Class#new" over rb_class_new_instance in decoding (#7352)
  * Build extensions for Ruby 2.7 (#7027)
  * assigning 'nil' to submessage should clear the field. (#7397)

  C#
  * [experimental] Add support for proto3 presence fields in C# (#7382)
  * Mark GetOption API as obsolete and expose the "GetOptions()" method on descriptors instead (#7491)
  * Remove Has/Clear members for C# message fields in proto2 (#7429)
  * Enforce recursion depth checking for unknown fields (#7132)
  * Fix conformance test failures for Google.Protobuf (#6910)
  * Cleanup various bits of Google.Protobuf (#6674)
  * Fix latest ArgumentException for C# extensions (#6938)
  * Remove unnecessary branch from ReadTag (#7289)

  Objective-C
  * [experimental] ObjC Proto3 optional support (#7421)
  * Block subclassing of generated classes (#7124)
  * Use references to Obj C classes instead of names in descriptors. (#7026)
  * Revisit how the WKTs are bundled with ObjC. (#7173)

  Other
  * Add a proto_lang_toolchain for javalite (#6882)
  * [bazel] Update gtest and deprecate //external:{gtest,gtest_main} (#7237)
  * Add application note for explicit presence tracking. (#7390)
  * Howto doc for implementing proto3 presence in a code generator. (#7407)


2020-02-14 version 3.11.4 (C++/Java/Python/PHP/Objective-C/C#/Ruby/JavaScript)
  
  C#
  * Fix latest ArgumentException for C# extensions (#7188)
  * Enforce recursion depth checking for unknown fields (#7210)
  
  Ruby
  * Fix wrappers with a zero value (#7195)
  * Fix JSON serialization of 0/empty-valued wrapper types (#7198)

2020-01-31 version 3.11.3 (C++/Java/Python/PHP/Objective-C/C#/Ruby/JavaScript)

  C++
  * Add OUT and OPTIONAL to windows portability files (#7087)

  PHP
  * Refactored ulong to zend_ulong for php7.4 compatibility (#7147)
  * Call register_class before getClass from desc to fix segfault (#7077)
  

2019-12-10 version 3.11.2 (C++/Java/Python/PHP/Objective-C/C#/Ruby/JavaScript)

  PHP
  * Make c extension portable for php 7.4 (#6968)
  

2019-12-02 version 3.11.1 (C++/Java/Python/PHP/Objective-C/C#/Ruby/JavaScript)

  PHP
  * Extern declare protobuf_globals (#6946)


2019-11-19 version 3.11.0 (C++/Java/Python/PHP/Objective-C/C#/Ruby/JavaScript)

  C++
  * Make serialization method naming consistent
  * Make proto runtime + generated code free of deprecation warnings
  * Moved ShutdownProtobufLibrary() to message_lite.h.  For backward compatibility a declaration is still available in stubs/common.h, but users should prefer message_lite.h
  * Removed non-namespace macro EXPECT_OK()
  * Removed mathlimits.h from stubs in favor of using std::numeric_limits from C++11
  * Fixed bug in parser when ending on a group tag
  * Add a helper function to UnknownFieldSet to deal with the changing return value of message::unknown_fields()
  * Fix incorrect use of string_view iterators
  * Support direct pickling of nested messages
  * Skip extension tag validation for MessageSet if unknown dependencies are allowed
  * Updated deprecation macros to annotate deprecated code (#6612)
  * Remove conversion warning in MapEntryFuncs::ByteSizeLong (#6766)
  * Revert "Make shared libraries be able to link to MSVC static runtime libraries, so that VC runtime is not required." (#6914)

  Java
  * Remove the usage of MethodHandle, so that Android users prior to API version 26 can use protobuf-java
  * Publish ProGuard config for javalite
  * Fix for StrictMode disk read violation in ExtensionRegistryLite
  * Include part of the ByteString's content in its toString().
  * Include unknown fields when merging proto3 messages in Java lite builders

  Python
  * Add float_precision option in json format printer
  * Optionally print bytes fields as messages in unknown fields, if possible
  * FieldPath: fix testing IsSet on root path ''
  * Experimental code gen (fast import protobuf module) which only work with cpp generated code linked in

  JavaScript
  * Remove guard for Symbol iterator for jspb.Map

  PHP
  * Avoid too much overhead in layout_init (#6716)
  * Lazily Create Singular Wrapper Message (#6833)
  * Implement lazy loading of php class for proto messages (#6911)

  Ruby
  * Ruby lazy wrappers optimization (#6797)

  C#
  * (RepeatedField): Capacity property to resize the internal array (#6530)
  * Experimental proto2 support is now officially available (#4642, #5183, #5350, #5936)
  * Getting started doc: https://github.com/protocolbuffers/protobuf/blob/master/docs/csharp/proto2.md
  * Add length checks to ExtensionCollection (#6759)
  * Optimize parsing of some primitive and wrapper types (#6843)
  * Use 3 parameter Encoding.GetString for default string values (#6828)
  * Change _Extensions property to normal body rather than expression (#6856)

  Objective C
  * Fixed unaligned reads for 32bit arm with newer Xcode versions (#6678)


2019-09-03 version 3.10.0 (C++/Java/Python/PHP/Objective-C/C#/Ruby/JavaScript)

  C++
  * Switch the proto parser to the faster MOMI parser.
  * Properly escape Struct keys in the proto3 JSON serializer.
  * Fix crash on uninitialized map entries.
  * Informed the compiler of has-bit invariant to produce better code
  * Unused imports of files defining descriptor extensions will now be reported
  * Add proto2::util::RemoveSubranges to remove multiple subranges in linear time.
  * Added BaseTextGenerator::GetCurrentIndentationSize()
  * Made implicit weak fields compatible with the Apple linker
  * Support 32 bit values for ProtoStreamObjectWriter to Struct.
  * Removed the internal-only header coded_stream_inl.h and the internal-only methods defined there.
  * Enforced no SWIG wrapping of descriptor_database.h (other headers already had this restriction).
  * Implementation of the equivalent of the MOMI parser for serialization. This removes one of the two serialization routines, by making the fast array serialization routine completely general. SerializeToCodedStream can now be implemented in terms of the much much faster array serialization. The array serialization regresses slightly, but when array serialization is not possible this wins big. 
  * Do not convert unknown field name to snake case to accurately report error.
  * Fix a UBSAN warnings. (#6333)
  * Add podspec for C++ (#6404)
  * protoc: fix source code info location for missing label (#6436)
  * C++ Add move constructor for Reflection's SetString (#6477)

  Java
  * Call loadDescriptor outside of synchronized block to remove one possible source of deadlock.
  * Have oneof enums implement a separate interface (other than EnumLite) for clarity.
  * Opensource Android Memory Accessors
  * Update TextFormat to make use of the new TypeRegistry.
  * Support getFieldBuilder and getRepeatedFieldBuilder in ExtendableBuilder
  * Update JsonFormat to make use of the new TypeRegistry.
  * Add proguard config generator for GmmBenchmarkSuiteLite.
  * Change ProtobufArrayList to use Object[] instead of ArrayList for 5-10% faster parsing
  * Implement ProtobufArrayList.add(E) for 20% (5%-40%) faster overall protolite2 parsing
  * Make a copy of JsonFormat.TypeRegistry at the protobuf top level package. This will eventually replace JsonFormat.TypeRegistry.
  * Fix javadoc warnings in generated files (#6231)
  * Java: Add Automatic-Module-Name entries to the Manifest (#6568)

  Python
  * Add descriptor methods in descriptor_pool are deprecated.
  * Uses explicit imports to prevent multithread test failures in py3.
  * Added __delitem__ for Python extension dict
  * Update six version to 1.12.0 and fix legacy_create_init issue (#6391)

  JavaScript
  * Remove deprecated boolean option to getResultBase64String().
  * Fix sint64 zig-zag encoding.
  * Simplify hash64 string conversion to avoid DIGIT array. Should reduce overhead if these functions aren't used, and be more efficient by avoiding linear array searches.
  * Change the parameter types of binaryReaderFn in ExtensionFieldBinaryInfo to (number, ?, ?).
  * Create dates.ts and time_of_days.ts to mirror Java versions. This is a near-identical conversion of c.g.type.util.{Dates,TimeOfDays} respectively.
  * Migrate moneys to TypeScript.
  
  PHP
  * Fix incorrect leap day for Timestamp (#6696)
  * Initialize well known type values (#6713)

  Ruby
  * Fix scope resolution for Google namespace (#5878)
  * Support hashes for struct initializers (#5716)
  * Optimized away the creation of empty string objects. (#6502)
  * Roll forward Ruby upb changes now that protobuf Ruby build is fixed (#5866)
  * Optimized layout_mark() for Ruby (#6521)
  * Optimization for layout_init() (#6547)
  * Fix for GC of Ruby map frames. (#6533)
  * Fixed leap year handling by reworking upb_mktime() -> upb_timegm(). (#6695)
  
  Objective C
  * Remove OSReadLittle* due to alignment requirements (#6678)
  * Don't use unions and instead use memcpy for the type swaps. (#6672)

  Other
  * Override CocoaPods module to lowercase (#6464)


2019-06-28 version 3.9.0 (C++/Java/Python/PHP/Objective-C/C#/Ruby/JavaScript)

  C++
  * Optimize and simplify implementation of RepeatedPtrFieldBase
  * Don't create unnecessary unknown field sets.
  * Remove branch from accessors to repeated field element array.
  * Added delimited parse and serialize util.
  * Reduce size by not emitting constants for fieldnumbers
  * Fix a bug when comparing finite and infinite field values with explicit tolerances.
  * TextFormat::Parser should use a custom Finder to look up extensions by number if one is provided.
  * Add MessageLite::Utf8DebugString() to make MessageLite more compatible with Message.
  * Fail fast for better performance in DescriptorPool::FindExtensionByNumber() if descriptor has no defined extensions.
  * Adding the file name to help debug colliding extensions
  * Added FieldDescriptor::PrintableNameForExtension() and DescriptorPool::FindExtensionByPrintableName().
    The latter will replace Reflection::FindKnownExtensionByName().
  * Replace NULL with nullptr
  * Created a new Add method in repeated field that allows adding a range of elements all at once.
  * Enabled enum name-to-value mapping functions for C++ lite
  * Avoid dynamic initialization in descriptor.proto generated code
  * Move stream functions to MessageLite from Message.
  * Move all zero_copy_stream functionality to io_lite.
  * Do not create array of matched fields for simple repeated fields
  * Enabling silent mode by default to reduce make compilation noise. (#6237)

  Java
  * Expose TextFormat.Printer and make it configurable. Deprecate the static methods.
  * Library for constructing google.protobuf.Struct and google.protobuf.Value
  * Make OneofDescriptor extend GenericDescriptor.
  * Expose streamingness of service methods from MethodDescriptor.
  * Fix a bug where TextFormat fails to parse Any filed with > 1 embedded message sub-fields.
  * Establish consistent JsonFormat behavior for nulls in oneofs, regardless of order.
  * Update GSON version to 3.8.5. (#6268)
  * Add `protobuf_java_lite` Bazel target. (#6177)

  Python
  * Change implementation of Name() for enums that allow aliases in proto2 in Python
    to be in line with claims in C++ implementation (to return first value).
  * Explicitly say what field cannot be set when the new value fails a type check.
  * Duplicate register in descriptor pool will raise errors
  * Add __slots__ to all well_known_types classes, custom attributes are not allowed anymore.
  * text_format only present 8 valid digits for float fields by default

  JavaScript
  * Add Oneof enum to the list of goog.provide

  PHP
  * Make php message class final to avoid mocking. (#6277)
  * Rename get/setXXXValue to get/setXXXWrapper. (#6295)

  Ruby
  * Remove to_hash methods. (#6166)


2019-04-29 version 3.8.0 (C++/Java/Python/PHP/Objective-C/C#/Ruby/JavaScript)

  C++
  * Use std::atomic<int32> in case of myriad2 platform
  * Always declare enums to be int-sized
  * Added DebugString() and ShortDebugString() methods on MessageLite
  * Specialized different parse loop control flows
  * Make hasbits potentially in register. The or's start forming an obstacle because it's a read modify store on the same mem address on each iteration.
  * Move to an internal MACRO for parser validity checks.
  * Improve map parsing performance.
  * Make MergePartialFromCodedStream non virtual. This allows direct calls, potential inlining and is also a code health improvement
  * Add an overall limit to parse_context to prevent reading past it. This allows to remove a annoying level of indirection.
  * Fix a mistake, we shouldn't verify map key/value strings for utf8 in opt mode for proto2.
  * Further improvements to cut binary size.
  * Prepare to make MergePartialFromCodedStream non-virtual.
  * A report on some interesting behavior change in python (caused by b/27494216) made me realize there is a check that needs to be done in case the parse ended on a end group tag.
  * Add a note of caution to the comments around skip in CodedOutputStream.
  * Simplify end check.
  * Add overload for ParseMessage for MessageLite/Message types. If the explicit type is not known inlining won't help de-virtualizing the virtual call.
  * Reduce linker input. It turns out that ParseMessage is not inlined, producing  template instantiations that are used only once and save nothing but cost more.
  * Improve the parser.
  * [c++17] Changed proto2::RepeatedPtrField iterators to no longer derive from the deprecated std::iterator class.
  * Change the default value of case_insensitive_enum_parsing to false for JsonStringToMessage.
  * Add a warning if a field name doesn't match the style guide.
  * Fix TextFormat not round-trip correctly when float value is max float.
  * Added locationed info for some errors at compiler
  * Python reserved keywords are now working with getattr()/setattr() for most descriptors.
  * Added AllowUnknownField() in text_format
  * Append '_' to C++ reserved keywords for message, enum, extension
  * Fix MSVC warning C4244 in protobuf's parse_context.h.
  * Updating Iterators to be compatible with C++17 in MSVC.
  * Use capability annotation in mutex.h
  * Fix "UndefinedBehaviorSanitizer: cfi-bad-type"
  * CriticalSectionLock class as a lightweight replacement for std::mutex on Windows platforms.
  * Removed vestigial wire_format_lite_inl.h

  C#
  * Added System.Memory dependency.

  Java
  * Make Java protoc code generator ignore optimize_for LITE_RUNTIME. Users should instead use the Java lite protoc plugin.
  * Change Extension getMessageDefaultInstance() to return Message instead of MessageLite.
  * Prevent malicious input streams from leaking buffers for ByteString or ByteBuffer parsing.
  * Release new Javalite runtime.
  * Show warning in case potential file name conflict.
  * Allow Java reserved keywords to be used in extensions.
  * Added setAllowUnknownFields() in text format
  * Add memoization to ExtensionRegistryLite.getEmptyRegistry()
  * Improve performance of CodedOutputStream.writeUInt32NoTag
  * Add an optimized mismatch-finding algorithm to UnsafeUtil.
  * When serializing uint32 varints, check that we have MAX_VARINT32_SIZE bytes left, not just MAX_VARINT_SIZE.
  * Minor optimization to RopeByteString.PieceIterator

  JavaScript
  * Simplify generated toObject code when the default value is used.

  Python
  * Changes implementation of Name() for enums that allow aliases in proto2 in Python to be in line with claims in C++ implementation (to return first value).
  * Added double_format option in text format printer.
  * Added iter and __contains__ to extension dict
  * Added allow_unknown_field option in python text format parser
  * Fixed Timestamp.ToDatetime() loses precision issue
  * Support unknown field in text format printer.
  * Float field will be convert to inf if bigger than struct.unpack('f', b'\xff\xff\x7f\x7f')[0] which is about 3.4028234664e+38,
  convert to -inf if smaller than -3.4028234664e+38
  * Allowed casting str->bytes in Message.__setstate__

  Ruby
  * Helper methods to get enum name for Ruby.


2019-01-24 version 3.7.0 (C++/Java/Python/PHP/Objective-C/C#/Ruby/JavaScript)

  C++
  * Introduced new MOMI (maybe-outside-memory-interval) parser.
  * Add an option to json_util to parse enum as case-insensitive. In the future, enum parsing in json_util will become case-sensitive.
  * Added conformance test for enum aliases
  * Added support for --cpp_out=speed:...
  * Added use of C++ override keyword where appropriate
  * Many other cleanups and fixes.

  Java
  * Fix illegal reflective access warning in JDK 9+
  * Add BOM

  Python
  * Added Python 3.7 compatibility.
  * Modified ParseFromString to return bytes parsed .
  * Introduce Proto C API.
  * FindFileContainingSymbol in descriptor pool is now able to find field and enum values.
  * reflection.MakeClass()  and  reflection.ParseMessage() are deprecated.
  * Added DescriptorPool.FindMethodByName() method in pure python (c extension already has it)
  * Flipped proto3 to preserve unknown fields by default.
  * Added support for memoryview in python3 proto message parsing.
  * Added MergeFrom for repeated scalar fields in c extension (pure python already has it)
  * Surrogates are now rejected at setters in python3.
  * Added public unknown field API.
  * RecursionLimit is also set to max if allow_oversize_protos is enabled.
  * Disallow duplicate scalars in proto3 text_format parse.
  * Fix some segment faults for c extension map field.

  PHP
  * Most issues for json encoding/decoding in the c extension have been fixed. There are still some edge cases not fixed. For more details, check conformance/failure_list_php_c.txt.
  * Supports php 7.3
  * Added helper methods to convert between enum values and names.
  * Allow setting/getting wrapper message fields using primitive values.
  * Various bug fixes.

  Ruby
  * Ruby 2.6 support.
  * Drops support for ruby < 2.3.
  * Most issues for json encoding/decoding in the c extension have been fixed. There are still some edge cases not fixed. For more details, check conformance/failure_list_ruby.txt.
  * Json parsing can specify an option to ignore unknown fields: msg.decode_json(data, {ignore_unknown_fields: true}).
  * Added support for proto2 syntax (partially).
  * Various bug fixes.

  Csharp
  * More support for FieldMask include merge, intersect and more.
  * Increasing the default recursion limit to 100.
  * Support loading FileDescriptors dynamically.
  * Provide access to comments from descriptors.
  * Added Any.Is method.
  * Compatible with C# 6
  * Added IComparable and comparison operators on Timestamp.

  Objective C
  * Add ability to introspect list of enum values (#4678)
  * Copy the value when setting message/data fields (#5215)
  * Support suppressing the objc package prefix checks on a list of files (#5309)
  * More complete keyword and NSObject method (via categories) checks for field names, can result in more fields being rename, but avoids the collisions at runtime (#5289)
  * Small fixes to TextFormat generation for extensions (#5362)
  * Provide more details/context in deprecation messages (#5412)
  * Array/Dictionary enumeration blocks NS_NOESCAPE annotation for Swift (#5421)
  * Properly annotate extensions for ARC when their names imply behaviors (#5427)
  * Enum alias name collision improvements (#5480)


2018-07-27 version 3.6.1 (C++/Java/Python/PHP/Objective-C/C#/Ruby/JavaScript)

  C++
  * Introduced workaround for Windows issue with std::atomic and std::once_flag
    initialization (#4777, #4773).

  PHP
  * Added compatibility with PHP 7.3 (#4898).

  Ruby
  * Fixed Ruby crash involving Any encoding (#4718).

2018-06-01 version 3.6.0 (C++/Java/Python/PHP/Objective-C/C#/Ruby/JavaScript)

  C++
  * Starting from this release, we now require C++11. For those we cannot yet
    upgrade to C++11, we will try to keep the 3.5.x branch updated with
    critical bug fixes only. If you have any concerns about this, please
    comment on issue #2780.
  * Moved to C++11 types like std::atomic and std::unique_ptr and away from our
    old custom-built equivalents.
  * Added support for repeated message fields in lite protos using implicit
    weak fields. This is an experimental feature that allows the linker to
    strip out more unused messages than previously was possible.
  * Fixed SourceCodeInfo for interpreted options and extension range options.
  * Fixed always_print_enums_as_ints option for JSON serialization.
  * Added support for ignoring unknown enum values when parsing JSON.
  * Create std::string in Arena memory.
  * Fixed ValidateDateTime to correctly check the day.
  * Fixed bug in ZeroCopyStreamByteSink.
  * Various other cleanups and fixes.

  Java
  * Dropped support for Java 6.
  * Added a UTF-8 decoder that uses Unsafe to directly decode a byte buffer.
  * Added deprecation annotations to generated code for deprecated oneof
    fields.
  * Fixed map field serialization in DynamicMessage.
  * Cleanup and documentation for Java Lite runtime.
  * Various other fixes and cleanups
  * Fixed unboxed arraylists to handle an edge case
  * Improved performance for copying between unboxed arraylists
  * Fixed lite protobuf to avoid Java compiler warnings
  * Improved test coverage for lite runtime
  * Performance improvements for lite runtime

  Python
  * Fixed bytes/string map key incompatibility between C++ and pure-Python
    implementations (issue #4029)
  * Added __init__.py files to compiler and util subpackages
  * Use /MT for all Windows versions
  * Fixed an issue affecting the Python-C++ implementation when used with
    Cython (issue #2896)
  * Various text format fixes
  * Various fixes to resolve behavior differences between the pure-Python and
    Python-C++ implementations

  PHP
  * Added php_metadata_namespace to control the file path of generated metadata
    file.
  * Changed generated classes of nested message/enum. E.g., Foo.Bar, which
    previously generates Foo_Bar, now generates Foo/Bar
  * Added array constructor. When creating a message, users can pass a php
    array whose content is field name to value pairs into constructor. The
    created message will be initialized according to the array. Note that
    message field should use a message value instead of a sub-array.
  * Various bug fixes.

  Objective-C
  * We removed some helper class methods from GPBDictionary to shrink the size
    of the library, the functionary is still there, but you may need to do some
    specific +alloc / -init… methods instead.
  * Minor improvements in the performance of object field getters/setters by
    avoiding some memory management overhead.
  * Fix a memory leak during the raising of some errors.
  * Make header importing completely order independent.
  * Small code improvements for things the undefined behaviors compiler option
    was flagging.

  Ruby
  * Added ruby_package file option to control the module of generated class.
  * Various bug fixes.

  Javascript
  * Allow setting string to int64 field.

  Csharp
  * Unknown fields are now parsed and then sent back on the wire. They can be
    discarded at parse time via a CodedInputStream option.
  * Movement towards working with .NET 3.5 and Unity
  * Expression trees are no longer used
  * AOT generics issues in Unity/il2cpp have a workaround (see this commit for
    details)
  * Floating point values are now compared bitwise (affects NaN value
    comparisons)
  * The default size limit when parsing is now 2GB rather than 64MB
  * MessageParser now supports parsing from a slice of a byte array
  * JSON list parsing now accepts null values where the underlying proto
    representation does

2017-12-20 version 3.5.1 (C++/Java/Python/PHP/Objective-C/C#/Ruby/JavaScript)
  Planned Future Changes
  * Make C++ implementation C++11 only: we plan to require C++11 to build
    protobuf code starting from 3.6.0 release. Please join this github issue:
    https://github.com/protocolbuffers/protobuf/issues/2780 to provide your feedback.

  protoc
  * Fixed a bug introduced in 3.5.0 and protoc in Windows now accepts non-ascii
    characters in paths again.

  C++
  * Removed several usages of C++11 features in the code base.
  * Fixed some compiler warnings.

  PHP
  * Fixed memory leak in C-extension implementation.
  * Added discardUnknokwnFields API.
  * Removed duplicated typedef in C-extension headers.
  * Avoided calling private php methods (timelib_update_ts).
  * Fixed Any.php to use fully-qualified name for DescriptorPool.

  Ruby
  * Added Google_Protobuf_discard_unknown for discarding unknown fields in
    messages.

  C#
  * Unknown fields are now preserved by default.
  * Floating point values are now bitwise compared, affecting message equality
    check and Contains() API in map and repeated fields.


2017-11-13 version 3.5.0 (C++/Java/Python/PHP/Objective-C/C#/Ruby/JavaScript)
  Planned Future Changes
  * Make C++ implementation C++11 only: we plan to require C++11 to build
    protobuf code starting from 3.6.0 release. Please join this github issue:
    https://github.com/protocolbuffers/protobuf/issues/2780 to provide your feedback.

  General
  * Unknown fields are now preserved in proto3 for most of the language
    implementations for proto3 by default. See the per-language section for
    details.
  * reserve keyword are now supported in enums

  C++
  * Proto3 messages are now preserving unknown fields by default. If you rely on
    unknowns fields being dropped. Please use DiscardUnknownFields() explicitly.
  * Deprecated the unsafe_arena_release_* and unsafe_arena_add_allocated_*
    methods for string fields.
  * Added move constructor and move assignment to RepeatedField,
    RepeatedPtrField and google::protobuf::Any.
  * Added perfect forwarding in Arena::CreateMessage
  * In-progress experimental support for implicit weak fields with lite protos.
    This feature allows the linker to strip out more unused messages and reduce
    binary size.
  * Various performance optimizations.

  Java
  * Proto3 messages are now preserving unknown fields by default. If you’d like
    to drop unknown fields, please use the DiscardUnknownFieldsParser API. For
    example:
      Parser<Foo> parser = DiscardUnknownFieldsParser.wrap(Foo.parser());
      Foo foo = parser.parseFrom(input);
  * Added a new CodedInputStream decoder for Iterable<ByteBuffer> with direct
    ByteBuffers.
  * TextFormat now prints unknown length-delimited fields as messages if
    possible.
  * FieldMaskUtil.merge() no longer creates unnecessary empty messages when a
    message field is unset in both source message and destination message.
  * Various performance optimizations.

  Python
  * Proto3 messages are now preserving unknown fields by default. Use
    message.DiscardUnknownFields() to drop unknown fields.
  * Add FieldDescriptor.file in generated code.
  * Add descriptor pool FindOneofByName in pure python.
  * Change unknown enum values into unknown field set .
  * Add more Python dict/list compatibility for Struct/ListValue.
  * Add utf-8 support for text_format.Merge()/Parse().
  * Support numeric unknown enum values for proto3 JSON format.
  * Add warning for Unexpected end-group tag in cpp extension.

  PHP
  * Proto3 messages are now preserving unknown fields.
  * Provide well known type messages in runtime.
  * Add prefix ‘PB’ to generated class of reserved names.
  * Fixed all conformance tests for encode/decode json in php runtime. C
    extension needs more work.

  Objective-C
  * Fixed some issues around copying of messages with unknown fields and then
    mutating the unknown fields in the copy.

  C#
  * Added unknown field support in JsonParser.
  * Fixed oneof message field merge.
  * Simplify parsing messages from array slices.

  Ruby
  * Unknown fields are now preserved by default.
  * Fixed several bugs for segment fault.

  Javascript
  * Decoder can handle both paced and unpacked data no matter how the proto is
    defined.
  * Decoder now accept long varint for 32 bit integers.


2017-08-14 version 3.4.0 (C++/Java/Python/PHP/Objective-C/C#/Ruby/JavaScript)
  Planned Future Changes
  * There are some changes that are not included in this release but are planned
    for the near future
      - Preserve unknown fields in proto3: We are going to bring unknown fields
        back into proto3. In this release, some languages start to support
        preserving unknown fields in proto3, controlled by flags/options. Some
        languages also introduce explicit APIs to drop unknown fields for
        migration. Please read the change log sections by languages for details.
        For general timeline and plan:

          https://docs.google.com/document/d/1KMRX-G91Aa-Y2FkEaHeeviLRRNblgIahbsk4wA14gRk/view

        For issues and discussions:

          https://github.com/protocolbuffers/protobuf/issues/272

      - Make C++ implementation C++11 only: we plan to require C++11 to build
        protobuf code starting from 3.5.0 or 3.6.0 release, after unknown fields
        semantic changes are finished. Please join this
        github issue:

          https://github.com/protocolbuffers/protobuf/issues/2780

        to provide your feedback.

  General
  * Extension ranges now accept options and are customizable.
  * "reserve" keyword now supports “max” in field number ranges,
    e.g.  reserve 1000 to max;

  C++
  * Proto3 messages are now able to preserve unknown fields. The default
    behavior is still to drop unknowns, which will be flipped in a future
    release. If you rely on unknowns fields being dropped. Please use
    Message::DiscardUnknownFields() explicitly.
  * Packable proto3 fields are now packed by default in serialization.
  * Following C++11 features are introduced when C++11 is available:
      - move-constructor and move-assignment are introduced to messages
      - Repeated fields constructor now takes std::initializer_list
      - rvalue setters are introduced for string fields
  * Experimental Table-Driven parsing and serialization available to test. To
    enable it, pass in table_driven_parsing table_driven_serialization protoc
    generator flags for C++

      $ protoc --cpp_out=table_driven_parsing,table_driven_serialization:./ \
        test.proto

  * lite generator parameter supported by the generator. Once set, all generated
    files, use lite runtime regardless of the optimizer_for setting in the
    .proto file.
  * Various optimizations to make C++ code more performant on PowerPC platform
  * Fixed maps data corruption when the maps are modified by both reflection API
    and generated API.
  * Deterministic serialization on maps reflection now uses stable sort.
  * file() accessors are introduced to various *Descriptor classes to make
    writing template function easier.
  * ByteSize() and SpaceUsed() are deprecated.Use ByteSizeLong() and
    SpaceUsedLong() instead
  * Consistent hash function is used for maps in DEBUG and NDEBUG build.
  * "using namespace std" is removed from stubs/common.h
  * Various performance optimizations and bug fixes

  Java
  * Introduced new parser API DiscardUnknownFieldsParser in preparation of
    proto3 unknown fields preservation change. Users who want to drop unknown
    fields should migrate to use this new parser API. For example:

      Parser<Foo> parser = DiscardUnknownFieldsParser.wrap(Foo.parser());
      Foo foo = parser.parseFrom(input);

  * Introduced new TextFormat API printUnicodeFieldValue() that prints field
    value without escaping unicode characters.
  * Added Durations.compare(Duration, Duration) and
    Timestamps.compare(Timestamp, Timestamp).
  * JsonFormat now accepts base64url encoded bytes fields.
  * Optimized CodedInputStream to do less copies when parsing large bytes
    fields.
  * Optimized TextFormat to allocate less memory when printing.

  Python
  * SerializeToString API is changed to SerializeToString(self, **kwargs),
    deterministic parameter is accepted for deterministic serialization.
  * Added sort_keys parameter in json format to make the output deterministic.
  * Added indent parameter in json format.
  * Added extension support in json format.
  * Added __repr__ support for repeated field in cpp implementation.
  * Added file in FieldDescriptor.
  * Added pretty-print filter to text format.
  * Services and method descriptors are always printed even if generic_service
    option is turned off.
  * Note: AppEngine 2.5 is deprecated on June 2017 that AppEngine 2.5 will
    never update protobuf runtime. Users who depend on AppEngine 2.5 should use
    old protoc.

  PHP
  * Support PHP generic services. Specify file option php_generic_service=true
    to enable generating service interface.
  * Message, repeated and map fields setters take value instead of reference.
  * Added map iterator in c extension.
  * Support json  encode/decode.
  * Added more type info in getter/setter phpdoc
  * Fixed the problem that c extension and php implementation cannot be used
    together.
  * Added file option php_namespace to use custom php namespace instead of
    package.
  * Added fluent setter.
  * Added descriptor API in runtime for custom encode/decode.
  * Various bug fixes.

  Objective-C
  * Fix for GPBExtensionRegistry copying and add tests.
  * Optimize GPBDictionary.m codegen to reduce size of overall library by 46K
    per architecture.
  * Fix some cases of reading of 64bit map values.
  * Properly error on a tag with field number zero.
  * Preserve unknown fields in proto3 syntax files.
  * Document the exceptions on some of the writing apis.

  C#
  * Implemented IReadOnlyDictionary<K,V> in MapField<K,V>
  * Added TryUnpack method for Any message in addition to Unpack.
  * Converted C# projects to MSBuild (csproj) format.

  Ruby
  * Several bug fixes.

  Javascript
  * Added support of field option js_type. Now one can specify the JS type of a
    64-bit integer field to be string in the generated code by adding option
    [jstype = JS_STRING] on the field.

2017-04-05 version 3.3.0 (C++/Java/Python/PHP/Objective-C/C#/Ruby/JavaScript)
  Planned Future Changes
  * There are some changes that are not included in this release but are
    planned for the near future:
      - Preserve unknown fields in proto3: please read this doc:

          https://docs.google.com/document/d/1KMRX-G91Aa-Y2FkEaHeeviLRRNblgIahbsk4wA14gRk/view

        for the timeline and follow up this github issue:

          https://github.com/protocolbuffers/protobuf/issues/272

        for discussion.
      - Make C++ implementation C++11 only: we plan to require C++11 to build
        protobuf code starting from 3.4.0 or 3.5.0 release. Please join this
        github issue:

          https://github.com/protocolbuffers/protobuf/issues/2780

        to provide your feedback.

  C++
  * Fixed map fields serialization of DynamicMessage to correctly serialize
    both key and value regardless of their presence.
  * Parser now rejects field number 0 correctly.
  * New API Message::SpaceUsedLong() that’s equivalent to
    Message::SpaceUsed() but returns the value in size_t.
  * JSON support
    - New flag always_print_enums_as_ints in JsonPrintOptions.
    - New flag preserve_proto_field_names in JsonPrintOptions. It will instruct
      the JSON printer to use the original field name declared in the .proto
      file instead of converting them to lowerCamelCase when printing JSON.
    - JsonPrintOptions.always_print_primtive_fields now works for oneof message
      fields.
    - Fixed a bug that doesn’t allow different fields to set the same json_name
      value.
    - Fixed a performance bug that causes excessive memory copy when printing
      large messages.
  * Various performance optimizations.

  Java
  * Map field setters eagerly validate inputs and throw NullPointerExceptions
    as appropriate.
  * Added ByteBuffer overloads to the generated parsing methods and the Parser
    interface.
  * proto3 enum's getNumber() method now throws on UNRECOGNIZED values.
  * Output of JsonFormat is now locale independent.

  Python
  * Added FindServiceByName() in the pure-Python DescriptorPool. This works only
    for descriptors added with DescriptorPool.Add(). Generated descriptor_pool
    does not support this yet.
  * Added a descriptor_pool parameter for parsing Any in text_format.Parse().
  * descriptor_pool.FindFileContainingSymbol() now is able to find nested
    extensions.
  * Extending empty [] to repeated field now sets parent message presence.

  PHP
  * Added file option php_class_prefix. The prefix will be prepended to all
    generated classes defined in the file.
  * When encoding, negative int32 values are sign-extended to int64.
  * Repeated/Map field setter accepts a regular PHP array. Type checking is
    done on the array elements.
  * encode/decode are renamed to serializeToString/mergeFromString.
  * Added mergeFrom, clear method on Message.
  * Fixed a bug that oneof accessor didn’t return the field name that is
    actually set.
  * C extension now works with php7.
  * This is the first GA release of PHP. We guarantee that old generated code
    can always work with new runtime and new generated code.

  Objective-C
  * Fixed help for GPBTimestamp for dates before the epoch that contain
    fractional seconds.
  * Added GPBMessageDropUnknownFieldsRecursively() to remove unknowns from a
    message and any sub messages.
  * Addressed a threading race in extension registration/lookup.
  * Increased the max message parsing depth to 100 to match the other languages.
  * Removed some use of dispatch_once in favor of atomic compare/set since it
    needs to be heap based.
  * Fixes for new Xcode 8.3 warnings.

  C#
  * Fixed MapField.Values.CopyTo, which would throw an exception unnecessarily
    if provided exactly the right size of array to copy to.
  * Fixed enum JSON formatting when multiple names mapped to the same numeric
    value.
  * Added JSON formatting option to format enums as integers.
  * Modified RepeatedField<T> to implement IReadOnlyList<T>.
  * Introduced the start of custom option handling; it's not as pleasant as it
    might be, but the information is at least present. We expect to extend code
    generation to improve this in the future.
  * Introduced ByteString.FromStream and ByteString.FromStreamAsync to
    efficiently create a ByteString from a stream.
  * Added whole-message deprecation, which decorates the class with [Obsolete].

  Ruby
  * Fixed Message#to_h for messages with map fields.
  * Fixed memcpy() in binary gems to work for old glibc, without breaking the
    build for non-glibc libc’s like musl.

  Javascript
  * Added compatibility tests for version 3.0.0.
  * Added conformance tests.
  * Fixed serialization of extensions: we need to emit a value even if it is
    falsy (like the number 0).
  * Use closurebuilder.py in favor of calcdeps.py for compiling JavaScript.

2017-01-23 version 3.2.0 (C++/Java/Python/PHP/Ruby/Objective-C/C#/JavaScript/Lite)
  General
  * Added protoc version number to protoc plugin protocol. It can be used by
    protoc plugin to detect which version of protoc is used with the plugin and
    mitigate known problems in certain version of protoc.

  C++
  * The default parsing byte size limit has been raised from 64MB to 2GB.
  * Added rvalue setters for non-arena string fields.
  * Enabled debug logging for Android.
  * Fixed a double-free problem when using Reflection::SetAllocatedMessage()
    with extension fields.
  * Fixed several deterministic serialization bugs:
    * MessageLite::SerializeAsString() now respects the global deterministic
      serialization flag.
    * Extension fields are serialized deterministically as well.  Fixed protocol
      compiler to correctly report importing-self as an error.
  * Fixed FileDescriptor::DebugString() to print custom options correctly.
  * Various performance/codesize optimizations and cleanups.

  Java
  * The default parsing byte size limit has been raised from 64MB to 2GB.
  * Added recursion limit when parsing JSON.
  * Fixed a bug that enumType.getDescriptor().getOptions() doesn't have custom
    options.
  * Fixed generated code to support field numbers up to 2^29-1.

  Python
  * You can now assign NumPy scalars/arrays (np.int32, np.int64) to protobuf
    fields, and assigning other numeric types has been optimized for
    performance.
  * Pure-Python: message types are now garbage-collectable.
  * Python/C++: a lot of internal cleanup/refactoring.

  PHP (Alpha)
  * For 64-bit integers type (int64/uint64/sfixed64/fixed64/sint64), use PHP
    integer on 64-bit environment and PHP string on 32-bit environment.
  * PHP generated code also conforms to PSR-4 now.
  * Fixed ZTS build for c extension.
  * Fixed c extension build on Mac.
  * Fixed c extension build on 32-bit linux.
  * Fixed the bug that message without namespace is not found in the descriptor
    pool. (#2240)
  * Fixed the bug that repeated field is not iterable in c extension.
  * Message names Empty will be converted to GPBEmpty in generated code.
  * Added phpdoc in generated files.
  * The released API is almost stable. Unless there is large problem, we won't
    change it. See
    https://developers.google.com/protocol-buffers/docs/reference/php-generated
    for more details.

  Objective-C
  * Added support for push/pop of the stream limit on CodedInputStream for
    anyone doing manual parsing.

  C#
  * No changes.

  Ruby
  * Message objects now support #respond_to? for field getters/setters.
  * You can now compare “message == non_message_object” and it will return false
    instead of throwing an exception.
  * JRuby: fixed #hashCode to properly reflect the values in the message.

  Javascript
  * Deserialization of repeated fields no longer has quadratic performance
    behavior.
  * UTF-8 encoding/decoding now properly supports high codepoints.
  * Added convenience methods for some well-known types: Any, Struct, and
    Timestamp. These make it easier to convert data between native JavaScript
    types and the well-known protobuf types.

2016-09-23 version 3.1.0 (C++/Java/Python/PHP/Ruby/Objective-C/C#/JavaScript/Lite)
  General
  * Proto3 support in PHP (alpha).
  * Various bug fixes.

  C++
  * Added MessageLite::ByteSizeLong() that’s equivalent to
    MessageLite::ByteSize() but returns the value in size_t. Useful to check
    whether a message is over the 2G size limit that protobuf can support.
  * Moved default_instances to global variables. This allows default_instance
    addresses to be known at compile time.
  * Adding missing generic gcc 64-bit atomicops.
  * Restore New*Callback into google::protobuf namespace since these are used
    by the service stubs code
  * JSON support.
    * Fixed some conformance issues.
  * Fixed a JSON serialization bug for bytes fields.

  Java
  * Fixed a bug in TextFormat that doesn’t accept empty repeated fields (i.e.,
    “field: [ ]”).
  * JSON support
    * Fixed JsonFormat to do correct snake_case-to-camelCase conversion for
      non-style-conforming field names.
    * Fixed JsonFormat to parse empty Any message correctly.
    * Added an option to JsonFormat.Parser to ignore unknown fields.
  * Experimental API
    * Added UnsafeByteOperations.unsafeWrap(byte[]) to wrap a byte array into
      ByteString without copy.

  Python
  * JSON support
    * Fixed some conformance issues.

  PHP (Alpha)
  * We have added the proto3 support for PHP via both a pure PHP package and a
    native c extension. The pure PHP package is intended to provide usability
    to wider range of PHP platforms, while the c extension is intended to
    provide higher performance. Both implementations provide the same runtime
    APIs and share the same generated code. Users don’t need to re-generate
    code for the same proto definition when they want to switch the
    implementation later. The pure PHP package is included in the php/src
    directory, and the c extension is included in the php/ext directory.

    Both implementations provide idiomatic PHP APIs:
    * All messages and enums are defined as PHP classes.
    * All message fields can only be accessed via getter/setter.
    * Both repeated field elements and map elements are stored in containers
      that act like a normal PHP array.

    Unlike several existing third-party PHP implementations for protobuf, our
    implementations are built on a "strongly-typed" philosophy: message fields
    and array/map containers will throw exceptions eagerly when values of the
    incorrect type (not including those that can be type converted, e.g.,
    double <-> integer <-> numeric string) are inserted.

    Currently, pure PHP runtime supports php5.5, 5.6 and 7 on linux. C
    extension runtime supports php5.5 and 5.6 on linux.

    See php/README.md for more details about installment. See
    https://developers.google.com/protocol-buffers/docs/phptutorial for more
    details about APIs.

  Objective-C
  * Helpers are now provided for working the Any well known type (see
    GPBWellKnownTypes.h for the api additions).
  * Some improvements in startup code (especially when extensions aren’t used).

  Javascript
  * Fixed missing import of jspb.Map
  * Fixed valueWriterFn variable name

  Ruby
  * Fixed hash computation for JRuby's RubyMessage
  * Make sure map parsing frames are GC-rooted.
  * Added API support for well-known types.

  C#
  * Removed check on dependency in the C# reflection API.

2016-09-06 version 3.0.2 (C++/Java/Python/Ruby/Objective-C/C#/JavaScript/Lite)
  General
  * Various bug fixes.

  Objective C
  * Fix for oneofs in proto3 syntax files where fields were set to the zero
    value.
  * Fix for embedded null character in strings.
  * CocoaDocs support

  Ruby
  * Fixed memory corruption bug in parsing that could occur under GC pressure.

  Javascript
  * jspb.Map is now properly exported to CommonJS modules.

  C#
  * Removed legacy_enum_values flag.


2016-07-27 version 3.0.0 (C++/Java/Python/Ruby/Objective-C/C#/JavaScript/Lite)
  General
  * This log only contains changes since the beta-4 release. Summarized change
    log since the last stable release (v2.6.1) can be found in the github
    release page.

  Compatibility Notice
  * v3.0.0 is the first API stable release of the v3.x series. We do not expect
    any future API breaking changes.
  * For C++, Java Lite and Objective-C, source level compatibility is
    guaranteed.  Upgrading from v3.0.0 to newer minor version releases will be
    source compatible. For example, if your code compiles against protobuf
    v3.0.0, it will continue to compile after you upgrade protobuf library to
    v3.1.0.
  * For other languages, both source level compatibility and binary level
    compatibility are guaranteed. For example, if you have a Java binary built
    against protobuf v3.0.0. After switching the protobuf runtime binary to
    v3.1.0, your built binary should continue to work.
  * Compatibility is only guaranteed for documented API and documented
    behaviors. If you are using undocumented API (e.g., use anything in the C++
    internal namespace), it can be broken by minor version releases in an
    undetermined manner.

  Ruby
  * When you assign a string field `a.string_field = "X"`, we now call
    #encode(UTF-8) on the string and freeze the copy. This saves you from
    needing to ensure the string is already encoded as UTF-8. It also prevents
    you from mutating the string after it has been assigned (this is how we
    ensure it stays valid UTF-8).
  * The generated file for `foo.proto` is now `foo_pb.rb` instead of just
    `foo.rb`. This makes it easier to see which imports/requires are from
    protobuf generated code, and also prevents conflicts with any `foo.rb` file
    you might have written directly in Ruby. It is a backward-incompatible
    change: you will need to update all of your `require` statements.
  * For package names like `foo_bar`, we now translate this to the Ruby module
    `FooBar`. This is more idiomatic Ruby than what we used to do (`Foo_bar`).

  JavaScript
  * Scalar fields like numbers and boolean now return defaults instead of
    `undefined` or `null` when they are unset. You can test for presence
    explicitly by calling `hasFoo()`, which we now generate for scalar fields.

  Java Lite
  * Java Lite is now implemented as a separate plugin, maintained in the
    `javalite` branch. Both lite runtime and protoc artifacts will be available
    in Maven.

  C#
  * Target platforms now .NET 4.5, selected portable subsets and .NET Core.
  * legacy_enum_values option is no longer supported.

2016-07-15 version 3.0.0-beta-4 (C++/Java/Python/Ruby/Objective-C/C#/JavaScript)
  General
  * Added a deterministic serialization API for C++. The deterministic
    serialization guarantees that given a binary, equal messages will be
    serialized to the same bytes. This allows applications like MapReduce to
    group equal messages based on the serialized bytes. The deterministic
    serialization is, however, NOT canonical across languages; it is also
    unstable across different builds with schema changes due to unknown fields.
    Users who need canonical serialization, e.g. persistent storage in a
    canonical form, fingerprinting, etc, should define their own
    canonicalization specification and implement the serializer using reflection
    APIs rather than relying on this API.
  * Added OneofOptions. You can now define custom options for oneof groups.
      import "google/protobuf/descriptor.proto";
      extend google.protobuf.OneofOptions {
        optional int32 my_oneof_extension = 12345;
      }
      message Foo {
        oneof oneof_group {
          (my_oneof_extension) = 54321;
          ...
        }
      }

  C++ (beta)
  * Introduced a deterministic serialization API in
    CodedOutputStream::SetSerializationDeterministic(bool). See the notes about
    deterministic serialization in the General section.
  * Added google::protobuf::Map::swap() to swap two map fields.
  * Fixed a memory leak when calling Reflection::ReleaseMessage() on a message
    allocated on arena.
  * Improved error reporting when parsing text format protos.
  * JSON
      - Added a new parser option to ignore unknown fields when parsing JSON.
      - Added convenient methods for message to/from JSON conversion.
  * Various performance optimizations.

  Java (beta)
  * File option "java_generate_equals_and_hash" is now deprecated. equals() and
    hashCode() methods are generated by default.
  * Added a new JSON printer option "omittingInsignificantWhitespace" to produce
    a more compact JSON output. The printer will pretty-print by default.
  * Updated Java runtime to be compatible with 2.5.0/2.6.1 generated protos.

  Python (beta)
  * Added support to pretty print Any messages in text format.
  * Added a flag to ignore unknown fields when parsing JSON.
  * Bugfix: "@type" field of a JSON Any message is now correctly put before
    other fields.

  Objective-C (beta)
  * Updated the code to support compiling with more compiler warnings
    enabled. (Issue 1616)
  * Exposing more detailed errors for parsing failures. (PR 1623)
  * Small (breaking) change to the naming of some methods on the support classes
    for map<>. There were collisions with the system provided KVO support, so
    the names were changed to avoid those issues.  (PR 1699)
  * Fixed for proper Swift bridging of error handling during parsing. (PR 1712)
  * Complete support for generating sources that will go into a Framework and
    depend on generated sources from other Frameworks. (Issue 1457)

  C# (beta)
  * RepeatedField optimizations.
  * Support for .NET Core.
  * Minor bug fixes.
  * Ability to format a single value in JsonFormatter (advanced usage only).
  * Modifications to attributes applied to generated code.

  Javascript (alpha)
  * Maps now have a real map API instead of being treated as repeated fields.
  * Well-known types are now provided in the google-protobuf package, and the
    code generator knows to require() them from that package.
  * Bugfix: non-canonical varints are correctly decoded.

  Ruby (alpha)
  * Accessors for oneof fields now return default values instead of nil.

  Java Lite
  * Java lite support is removed from protocol compiler. It will be supported
    as a protocol compiler plugin in a separate code branch.

2016-05-16 version 3.0.0-beta-3 (C++/Java/Python/Ruby/Nano/Objective-C/C#/JavaScript)
  General
  * Supported Proto3 lite-runtime in C++/Java for mobile platforms.
  * Any type now supports APIs to specify prefixes other than
    type.googleapis.com
  * Removed javanano_use_deprecated_package option; Nano will always has its own
    ".nano" package.

  C++ (Beta)
  * Improved hash maps.
      - Improved hash maps comments. In particular, please note that equal hash
        maps will not necessarily have the same iteration order and
        serialization.
      - Added a new hash maps implementation that will become the default in a
        later release.
  * Arenas
      - Several inlined methods in Arena were moved to out-of-line to improve
        build performance and code size.
      - Added SpaceAllocatedAndUsed() to report both space used and allocated
      - Added convenient class UnsafeArenaAllocatedRepeatedPtrFieldBackInserter
  * Any
      - Allow custom type URL prefixes in Any packing.
      - TextFormat now expand the Any type rather than printing bytes.
  * Performance optimizations and various bug fixes.

  Java (Beta)
  * Introduced an ExperimentalApi annotation. Annotated APIs are experimental
    and are subject to change in a backward incompatible way in future releases.
  * Introduced zero-copy serialization as an ExperimentalApi
      - Introduction of the `ByteOutput` interface. This is similar to
        `OutputStream` but provides semantics for lazy writing (i.e. no
        immediate copy required) of fields that are considered to be immutable.
      - `ByteString` now supports writing to a `ByteOutput`, which will directly
        expose the internals of the `ByteString` (i.e. `byte[]` or `ByteBuffer`)
        to the `ByteOutput` without copying.
      - `CodedOutputStream` now supports writing to a `ByteOutput`. `ByteString`
        instances that are too large to fit in the internal buffer will be
        (lazily) written to the `ByteOutput` directly.
      - This allows applications using large `ByteString` fields to avoid
        duplication of these fields entirely. Such an application can supply a
        `ByteOutput` that chains together the chunks received from
        `CodedOutputStream` before forwarding them onto the IO system.
  * Other related changes to `CodedOutputStream`
      - Additional use of `sun.misc.Unsafe` where possible to perform fast
        access to `byte[]` and `ByteBuffer` values and avoiding unnecessary
        range checking.
      - `ByteBuffer`-backed `CodedOutputStream` now writes directly to the
        `ByteBuffer` rather than to an intermediate array.
  * Improved lite-runtime.
      - Lite protos now implement deep equals/hashCode/toString
      - Significantly improved the performance of Builder#mergeFrom() and
        Builder#mergeDelimitedFrom()
  * Various bug fixes and small feature enhancement.
      - Fixed stack overflow when in hashCode() for infinite recursive oneofs.
      - Fixed the lazy field parsing in lite to merge rather than overwrite.
      - TextFormat now supports reporting line/column numbers on errors.
      - Updated to add appropriate @Override for better compiler errors.

  Python (Beta)
  * Added JSON format for Any, Struct, Value and ListValue
  * [ ] is now accepted for both repeated scalar fields and repeated message
    fields in text format parser.
  * Numerical field name is now supported in text format.
  * Added DiscardUnknownFields API for python protobuf message.

  Objective-C (Beta)
  * Proto comments now come over as HeaderDoc comments in the generated sources
    so Xcode can pick them up and display them.
  * The library headers have been updated to use HeaderDoc comments so Xcode can
    pick them up and display them.
  * The per message and per field overhead in both generated code and runtime
    object sizes was reduced.
  * Generated code now include deprecated annotations when the proto file
    included them.

  C# (Beta)
  In general: some changes are breaking, which require regenerating messages.
  Most user-written code will not be impacted *except* for the renaming of enum
  values.

  * Allow custom type URL prefixes in `Any` packing, and ignore them when
    unpacking
  * `protoc` is now in a separate NuGet package (Google.Protobuf.Tools)
  * New option: `internal_access` to generate internal classes
  * Enum values are now PascalCased, and if there's a prefix which matches the
    name of the enum, that is removed (so an enum `COLOR` with a value
    `COLOR_BLUE` would generate a value of just `Blue`). An option
    (`legacy_enum_values`) is temporarily available to disable this, but the
    option will be removed for GA.
  * `json_name` option is now honored
  * If group tags are encountered when parsing, they are validated more
    thoroughly (although we don't support actual groups)
  * NuGet dependencies are better specified
  * Breaking: `Preconditions` is renamed to `ProtoPreconditions`
  * Breaking: `GeneratedCodeInfo` is renamed to `GeneratedClrTypeInfo`
  * `JsonFormatter` now allows writing to a `TextWriter`
  * New interface, `ICustomDiagnosticMessage` to allow more compact
    representations from `ToString`
  * `CodedInputStream` and `CodedOutputStream` now implement `IDisposable`,
    which simply disposes of the streams they were constructed with
  * Map fields no longer support null values (in line with other languages)
  * Improvements in JSON formatting and parsing

  Javascript (Alpha)
  * Better support for "bytes" fields: bytes fields can be read as either a
    base64 string or UInt8Array (in environments where TypedArray is supported).
  * New support for CommonJS imports.  This should make it easier to use the
    JavaScript support in Node.js and tools like WebPack.  See js/README.md for
    more information.
  * Some significant internal refactoring to simplify and modularize the code.

  Ruby (Alpha)
  * JSON serialization now properly uses camelCased names, with a runtime option
    that will preserve original names from .proto files instead.
  * Well-known types are now included in the distribution.
  * Release now includes binary gems for Windows, Mac, and Linux instead of just
    source gems.
  * Bugfix for serializing oneofs.

  C++/Java Lite (Alpha)
    A new "lite" generator parameter was introduced in the protoc for C++ and
    Java for Proto3 syntax messages. Example usage:

     ./protoc --cpp_out=lite:$OUTPUT_PATH foo.proto

    The protoc will treat the current input and all the transitive dependencies
    as LITE. The same generator parameter must be used to generate the
    dependencies.

    In Proto3 syntax files, "optimized_for=LITE_RUNTIME" is no longer supported.


2015-12-30 version 3.0.0-beta-2 (C++/Java/Python/Ruby/Nano/Objective-C/C#/JavaScript)
  General
  * Introduced a new language implementation: JavaScript.
  * Added a new field option "json_name". By default proto field names are
    converted to "lowerCamelCase" in proto3 JSON format. This option can be
    used to override this behavior and specify a different JSON name for the
    field.
  * Added conformance tests to ensure implementations are following proto3 JSON
    specification.

  C++ (Beta)
  * Various bug fixes and improvements to the JSON support utility:
      - Duplicate map keys in JSON are now rejected (i.e., translation will
        fail).
      - Fixed wire-format for google.protobuf.Value/ListValue.
      - Fixed precision loss when converting google.protobuf.Timestamp.
      - Fixed a bug when parsing invalid UTF-8 code points.
      - Fixed a memory leak.
      - Reduced call stack usage.

  Java (Beta)
  * Cleaned up some unused methods on CodedOutputStream.
  * Presized lists for packed fields during parsing in the lite runtime to
    reduce allocations and improve performance.
  * Improved the performance of unknown fields in the lite runtime.
  * Introduced UnsafeByteStrings to support zero-copy ByteString creation.
  * Various bug fixes and improvements to the JSON support utility:
      - Fixed a thread-safety bug.
      - Added a new option “preservingProtoFieldNames” to JsonFormat.
      - Added a new option “includingDefaultValueFields” to JsonFormat.
      - Updated the JSON utility to comply with proto3 JSON specification.

  Python (Beta)
  * Added proto3 JSON format utility. It includes support for all field types
    and a few well-known types except for Any and Struct.
  * Added runtime support for Any, Timestamp, Duration and FieldMask.
  * [ ] is now accepted for repeated scalar fields in text format parser.
  * Map fields now have proper O(1) performance for lookup/insert/delete
    when using the Python/C++ implementation. They were previously using O(n)
    search-based algorithms because the C++ reflection interface didn't
    support true map operations.

  Objective-C (Beta)
  * Various bug-fixes and code tweaks to pass more strict compiler warnings.
  * Now has conformance test coverage and is passing all tests.

  C# (Beta)
  * Various bug-fixes.
  * Code generation: Files generated in directories based on namespace.
  * Code generation: Include comments from .proto files in XML doc
    comments (naively)
  * Code generation: Change organization/naming of "reflection class" (access
    to file descriptor)
  * Code generation and library: Add Parser property to MessageDescriptor,
    and introduce a non-generic parser type.
  * Library: Added TypeRegistry to support JSON parsing/formatting of Any.
  * Library: Added Any.Pack/Unpack support.
  * Library: Implemented JSON parsing.

  Javascript (Alpha)
  * Added proto3 support for JavaScript. The runtime is written in pure
    JavaScript and works in browsers and in Node.js. To generate JavaScript
    code for your proto, invoke protoc with "--js_out". See js/README.md
    for more build instructions.

2015-08-26 version 3.0.0-beta-1 (C++/Java/Python/Ruby/Nano/Objective-C/C#)
  About Beta
  * This is the first beta release of protobuf v3.0.0. Not all languages
    have reached beta stage. Languages not marked as beta are still in
    alpha (i.e., be prepared for API breaking changes).

  General
  * Proto3 JSON is supported in several languages (fully supported in C++
    and Java, partially supported in Ruby/C#). The JSON spec is defined in
    the proto3 language guide:

      https://developers.google.com/protocol-buffers/docs/proto3#json

    We will publish a more detailed spec to define the exact behavior of
    proto3-conformant JSON serializers and parsers. Until then, do not rely
    on specific behaviors of the implementation if it’s not documented in
    the above spec. More specifically, the behavior is not yet finalized for
    the following:
      - Parsing invalid JSON input (e.g., input with trailing commas).
      - Non-camelCase names in JSON input.
      - The same field appears multiple times in JSON input.
      - JSON arrays contain “null” values.
      - The message has unknown fields.

  * Proto3 now enforces strict UTF-8 checking. Parsing will fail if a string
    field contains non UTF-8 data.

  C++ (Beta)
  * Introduced new utility functions/classes in the google/protobuf/util
    directory:
      - MessageDifferencer: compare two proto messages and report their
                            differences.
      - JsonUtil: support converting protobuf binary format to/from JSON.
      - TimeUtil: utility functions to work with well-known types Timestamp
                  and Duration.
      - FieldMaskUtil: utility functions to work with FieldMask.

  * Performance optimization of arena construction and destruction.
  * Bug fixes for arena and maps support.
  * Changed to use cmake for Windows Visual Studio builds.
  * Added Bazel support.

  Java (Beta)
  * Introduced a new util package that will be distributed as a separate
    artifact in maven. It contains:
      - JsonFormat: convert proto messages to/from JSON.
      - TimeUtil: utility functions to work with Timestamp and Duration.
      - FieldMaskUtil: utility functions to work with FieldMask.

  * The static PARSER in each generated message is deprecated, and it will
    be removed in a future release. A static parser() getter is generated
    for each message type instead.
  * Performance optimizations for String fields serialization.
  * Performance optimizations for Lite runtime on Android:
      - Reduced allocations
      - Reduced method overhead after ProGuarding
      - Reduced code size after ProGuarding

  Python (Alpha)
  * Removed legacy Python 2.5 support.
  * Moved to a single Python 2.x/3.x-compatible codebase, instead of using 2to3.
  * Fixed build/tests on Python 2.6, 2.7, 3.3, and 3.4.
      - Pure-Python works on all four.
      - Python/C++ implementation works on all but 3.4, due to changes in the
        Python/C++ API in 3.4.
  * Some preliminary work has been done to allow for multiple DescriptorPools
    with Python/C++.

  Ruby (Alpha)
  * Many bugfixes:
      - fixed parsing/serialization of bytes, sint, sfixed types
      - other parser bugfixes
      - fixed memory leak affecting Ruby 2.2

  JavaNano (Alpha)
  * JavaNano generated code now will be put in a nano package by default to
    avoid conflicts with Java generated code.

  Objective-C (Alpha)
  * Added non-null markup to ObjC library. Requires SDK 8.4+ to build.
  * Many bugfixes:
      - Removed the class/enum filter.
      - Renamed some internal types to avoid conflicts with the well-known types
        protos.
      - Added missing support for parsing repeated primitive fields in packed or
        unpacked forms.
      - Added *Count for repeated and map<> fields to avoid auto-create when
        checking for them being set.

  C# (Alpha)
  * Namespace changed to Google.Protobuf (and NuGet package will be named
    correspondingly).
  * Target platforms now .NET 4.5 and selected portable subsets only.
  * Removed lite runtime.
  * Reimplementation to use mutable message types.
  * Null references used to represent "no value" for message type fields.
  * Proto3 semantics supported; proto2 files are prohibited for C# codegen.
    Most proto3 features supported:
      - JSON formatting (a.k.a. serialization to JSON), including well-known
        types (except for Any).
      - Wrapper types mapped to nullable value types (or string/ByteString
        allowing nullability). JSON parsing is not supported yet.
      - maps
      - oneof
      - enum unknown value preservation

2015-05-25 version 3.0.0-alpha-3 (Objective-C/C#):
  General
  * Introduced two new language implementations (Objective-C, C#) to proto3.
  * Explicit "optional" keyword are disallowed in proto3 syntax, as fields are
    optional by default.
  * Group fields are no longer supported in proto3 syntax.
  * Changed repeated primitive fields to use packed serialization by default in
    proto3 (implemented for C++, Java, Python in this release).  The user can
    still disable packed serialization by setting packed to false for now.
  * Added well-known type protos (any.proto, empty.proto, timestamp.proto,
    duration.proto, etc.). Users can import and use these protos just like
    regular proto files. Additional runtime support will be added for them in
    future releases (in the form of utility helper functions, or having them
    replaced by language specific types in generated code).
  * Added a "reserved" keyword in both proto2 and proto3 syntax. User can use
    this keyword to declare reserved field numbers and names to prevent them
    from being reused by other fields in the same message.

    To reserve field numbers, add a reserved declaration in your message:

      message TestMessage {
        reserved 2, 15, 9 to 11, 3;
      }

    This reserves field numbers 2, 3, 9, 10, 11 and 15. If a user uses any of
    these as field numbers, the protocol buffer compiler will report an error.

    Field names can also be reserved:

      message TestMessage {
        reserved "foo", "bar";
      }

  * Various bug fixes since 3.0.0-alpha-2

  Objective-C
    Objective-C includes a code generator and a native objective-c runtime
    library.  By adding “--objc_out” to protoc, the code generator will generate
    a header(*.pbobjc.h) and an implementation file(*.pbobjc.m) for each proto
    file.

    In this first release, the generated interface provides: enums, messages,
    field support(single, repeated, map, oneof), proto2 and proto3 syntax
    support, parsing and serialization. It’s  compatible with ARC and non-ARC
    usage. Besides, user can also access it via the swift bridging header.

    See objectivec/README.md for details.

  C#
    * C# protobufs are based on project
      https://github.com/jskeet/protobuf-csharp-port. The original project was
      frozen and all the new development will happen here.
    * Codegen plugin for C# was completely rewritten to C++ and is now an
      integral part of protoc.
    * Some refactorings and cleanup has been applied to the C# runtime library.
    * Only proto2 is supported in C# at the moment, proto3 support is in
      progress and will likely bring significant breaking changes to the API.

    See csharp/README.md for details.

  C++
    * Added runtime support for Any type. To use Any in your proto file, first
      import the definition of Any:

        // foo.proto
        import "google/protobuf/any.proto";
        message Foo {
          google.protobuf.Any any_field = 1;
        }
        message Bar {
          int32 value = 1;
        }

      Then in C++ you can access the Any field using PackFrom()/UnpackTo()
      methods:

        Foo foo;
        Bar bar = ...;
        foo.mutable_any_field()->PackFrom(bar);
        ...
        if (foo.any_field().IsType<Bar>()) {
          foo.any_field().UnpackTo(&bar);
          ...
        }
    * In text format, entries of a map field will be sorted by key.

  Java
    * Continued optimizations on the lite runtime to improve performance for
      Android.

  Python
    * Added map support.
      - maps now have a dict-like interface (msg.map_field[key] = value)
      - existing code that modifies maps via the repeated field interface
        will need to be updated.

  Ruby
    * Improvements to RepeatedField's emulation of the Ruby Array API.
    * Various speedups and internal cleanups.

2015-02-26 version 3.0.0-alpha-2 (Python/Ruby/JavaNano):
  General
  * Introduced three new language implementations (Ruby, JavaNano, and
    Python) to proto3.
  * Various bug fixes since 3.0.0-alpha-1

  Python:
    Python has received several updates, most notably support for proto3
    semantics in any .proto file that declares syntax="proto3".
    Messages declared in proto3 files no longer represent field presence
    for scalar fields (number, enums, booleans, or strings).  You can
    no longer call HasField() for such fields, and they are serialized
    based on whether they have a non-zero/empty/false value.

    One other notable change is in the C++-accelerated implementation.
    Descriptor objects (which describe the protobuf schema and allow
    reflection over it) are no longer duplicated between the Python
    and C++ layers.  The Python descriptors are now simple wrappers
    around the C++ descriptors.  This change should significantly
    reduce the memory usage of programs that use a lot of message
    types.

  Ruby:
    We have added proto3 support for Ruby via a native C extension.

    The Ruby extension itself is included in the ruby/ directory, and details on
    building and installing the extension are in ruby/README.md. The extension
    will also be published as a Ruby gem. Code generator support is included as
    part of `protoc` with the `--ruby_out` flag.

    The Ruby extension implements a user-friendly DSL to define message types
    (also generated by the code generator from `.proto` files).  Once a message
    type is defined, the user may create instances of the message that behave in
    ways idiomatic to Ruby. For example:

    - Message fields are present as ordinary Ruby properties (getter method
      `foo` and setter method `foo=`).
    - Repeated field elements are stored in a container that acts like a native
      Ruby array, and map elements are stored in a container that acts like a
      native Ruby hashmap.
    - The usual well-known methods, such as `#to_s`, `#dup`, and the like, are
      present.

    Unlike several existing third-party Ruby extensions for protobuf, this
    extension is built on a "strongly-typed" philosophy: message fields and
    array/map containers will throw exceptions eagerly when values of the
    incorrect type are inserted.

    See ruby/README.md for details.

  JavaNano:
    JavaNano is a special code generator and runtime library designed especially
    for resource-restricted systems, like Android. It is very resource-friendly
    in both the amount of code and the runtime overhead. Here is an an overview
    of JavaNano features compared with the official Java protobuf:

    - No descriptors or message builders.
    - All messages are mutable; fields are public Java fields.
    - For optional fields only, encapsulation behind setter/getter/hazzer/
      clearer functions is opt-in, which provide proper 'has' state support.
    - For proto2, if not opted in, has state (field presence) is not available.
      Serialization outputs all fields not equal to their defaults.
      The behavior is consistent with proto3 semantics.
    - Required fields (proto2 only) are always serialized.
    - Enum constants are integers; protection against invalid values only
      when parsing from the wire.
    - Enum constants can be generated into container interfaces bearing
      the enum's name (so the referencing code is in Java style).
    - CodedInputByteBufferNano can only take byte[] (not InputStream).
    - Similarly CodedOutputByteBufferNano can only write to byte[].
    - Repeated fields are in arrays, not ArrayList or Vector. Null array
      elements are allowed and silently ignored.
    - Full support for serializing/deserializing repeated packed fields.
    - Support  extensions (in proto2).
    - Unset messages/groups are null, not an immutable empty default
      instance.
    - toByteArray(...) and mergeFrom(...) are now static functions of
      MessageNano.
    - The 'bytes' type translates to the Java type byte[].

    See javanano/README.txt for details.

2014-12-01 version 3.0.0-alpha-1 (C++/Java):

  General
  * Introduced Protocol Buffers language version 3 (aka proto3).

    When protobuf was initially opensourced it implemented Protocol Buffers
    language version 2 (aka proto2), which is why the version number
    started from v2.0.0. From v3.0.0, a new language version (proto3) is
    introduced while the old version (proto2) will continue to be supported.

    The main intent of introducing proto3 is to clean up protobuf before
    pushing the language as the foundation of Google's new API platform.
    In proto3, the language is simplified, both for ease of use and  to
    make it available in a wider range of programming languages. At the
    same time a few features are added to better support common idioms
    found in APIs.

    The following are the main new features in language version 3:

      1. Removal of field presence logic for primitive value fields, removal
         of required fields, and removal of default values. This makes proto3
         significantly easier to implement with open struct representations,
         as in languages like Android Java, Objective C, or Go.
      2. Removal of unknown fields.
      3. Removal of extensions, which are instead replaced by a new standard
         type called Any.
      4. Fix semantics for unknown enum values.
      5. Addition of maps.
      6. Addition of a small set of standard types for representation of time,
         dynamic data, etc.
      7. A well-defined encoding in JSON as an alternative to binary proto
         encoding.

    This release (v3.0.0-alpha-1) includes partial proto3 support for C++ and
    Java. Items 6 (well-known types) and 7 (JSON format) in the above feature
    list are not implemented.

    A new notion "syntax" is introduced to specify whether a .proto file
    uses proto2 or proto3:

      // foo.proto
      syntax = "proto3";
      message Bar {...}

    If omitted, the protocol compiler will generate a warning and "proto2" will
    be used as the default. This warning will be turned into an error in a
    future release.

    We recommend that new Protocol Buffers users use proto3. However, we do not
    generally recommend that existing users migrate from proto2 from proto3 due
    to API incompatibility, and we will continue to support proto2 for a long
    time.

  * Added support for map fields (implemented in C++/Java for both proto2 and
    proto3).

    Map fields can be declared using the following syntax:

      message Foo {
        map<string, string> values = 1;
      }

    Data of a map field will be stored in memory as an unordered map and it
    can be accessed through generated accessors.

  C++
  * Added arena allocation support (for both proto2 and proto3).

    Profiling shows memory allocation and deallocation constitutes a significant
    fraction of CPU-time spent in protobuf code and arena allocation is a
    technique introduced to reduce this cost. With arena allocation, new
    objects will be allocated from a large piece of preallocated memory and
    deallocation of these objects is almost free. Early adoption shows 20% to
    50% improvement in some Google binaries.

    To enable arena support, add the following option to your .proto file:

      option cc_enable_arenas = true;

    Protocol compiler will generate additional code to make the generated
    message classes work with arenas. This does not change the existing API
    of protobuf messages and does not affect wire format. Your existing code
    should continue to work after adding this option. In the future we will
    make this option enabled by default.

    To actually take advantage of arena allocation, you need to use the arena
    APIs when creating messages. A quick example of using the arena API:

      {
        google::protobuf::Arena arena;
        // Allocate a protobuf message in the arena.
        MyMessage* message = Arena::CreateMessage<MyMessage>(&arena);
        // All submessages will be allocated in the same arena.
        if (!message->ParseFromString(data)) {
          // Deal with malformed input data.
        }
        // Must not delete the message here. It will be deleted automatically
        // when the arena is destroyed.
      }

    Currently arena does not work with map fields. Enabling arena in a .proto
    file containing map fields will result in compile errors in the generated
    code. This will be addressed in a future release.

2014-10-20 version 2.6.1:

  C++
  * Added atomicops support for Solaris.
  * Released memory allocated by InitializeDefaultRepeatedFields() and
    GetEmptyString(). Some memory sanitizers reported them as memory leaks.

  Java
  * Updated DynamicMessage.setField() to handle repeated enum values
    correctly.
  * Fixed a bug that caused NullPointerException to be thrown when
    converting manually constructed FileDescriptorProto to
    FileDescriptor.

  Python
  * Fixed WhichOneof() to work with de-serialized protobuf messages.
  * Fixed a missing file problem of Python C++ implementation.

2014-08-15 version 2.6.0:

  General
  * Added oneofs(unions) feature. Fields in the same oneof will share
    memory and at most one field can be set at the same time. Use the
    oneof keyword to define a oneof like:
      message SampleMessage {
        oneof test_oneof {
          string name = 4;
          YourMessage sub_message = 9;
        }
      }
  * Files, services, enums, messages, methods and enum values can be marked
    as deprecated now.
  * Added Support for list values, including lists of messages, when
    parsing text-formatted protos in C++ and Java.
      For example:  foo: [1, 2, 3]

  C++
  * Enhanced customization on TestFormat printing.
  * Added SwapFields() in reflection API to swap a subset of fields.
    Added SetAllocatedMessage() in reflection API.
  * Repeated primitive extensions are now packable. The
    [packed=true] option only affects serializers. Therefore, it is
    possible to switch a repeated extension field to packed format
    without breaking backwards-compatibility.
  * Various speed optimizations.

  Java
  * writeTo() method in ByteString can now write a substring to an
    output stream. Added endWith() method for ByteString.
  * ByteString and ByteBuffer are now supported in CodedInputStream
    and CodedOutputStream.
  * java_generate_equals_and_hash can now be used with the LITE_RUNTIME.

  Python
  * A new C++-backed extension module (aka "cpp api v2") that replaces the
    old ("cpp api v1") one.  Much faster than the pure Python code.  This one
    resolves many bugs and is recommended for general use over the
    pure Python when possible.
  * Descriptors now have enum_types_by_name and extension_types_by_name dict
    attributes.
  * Support for Python 3.

2013-02-27 version 2.5.0:

  General
  * New notion "import public" that allows a proto file to forward the content
    it imports to its importers. For example,
      // foo.proto
      import public "bar.proto";
      import "baz.proto";

      // qux.proto
      import "foo.proto";
      // Stuff defined in bar.proto may be used in this file, but stuff from
      // baz.proto may NOT be used without importing it explicitly.
    This is useful for moving proto files. To move a proto file, just leave
    a single "import public" in the old proto file.
  * New enum option "allow_alias" that specifies whether different symbols can
    be assigned the same numeric value. Default value is "true". Setting it to
    false causes the compiler to reject enum definitions where multiple symbols
    have the same numeric value.
    Note: We plan to flip the default value to "false" in a future release.
    Projects using enum aliases should set the option to "true" in their .proto
    files.

  C++
  * New generated method set_allocated_foo(Type* foo) for message and string
    fields. This method allows you to set the field to a pre-allocated object
    and the containing message takes the ownership of that object.
  * Added SetAllocatedExtension() and ReleaseExtension() to extensions API.
  * Custom options are now formatted correctly when descriptors are printed in
    text format.
  * Various speed optimizations.

  Java
  * Comments in proto files are now collected and put into generated code as
    comments for corresponding classes and data members.
  * Added Parser to parse directly into messages without a Builder. For
    example,
      Foo foo = Foo.PARSER.ParseFrom(input);
    Using Parser is ~25% faster than using Builder to parse messages.
  * Added getters/setters to access the underlying ByteString of a string field
    directly.
  * ByteString now supports more operations: substring(), prepend(), and
    append(). The implementation of ByteString uses a binary tree structure
    to support these operations efficiently.
  * New method findInitializationErrors() that lists all missing required
    fields.
  * Various code size and speed optimizations.

  Python
  * Added support for dynamic message creation. DescriptorDatabase,
    DescriptorPool, and MessageFactory work like their C++ counterparts to
    simplify Descriptor construction from *DescriptorProtos, and MessageFactory
    provides a message instance from a Descriptor.
  * Added pickle support for protobuf messages.
  * Unknown fields are now preserved after parsing.
  * Fixed bug where custom options were not correctly populated. Custom
    options can be accessed now.
  * Added EnumTypeWrapper that provides better accessibility to enum types.
  * Added ParseMessage(descriptor, bytes) to generate a new Message instance
    from a descriptor and a byte string.

2011-05-01 version 2.4.1:

  C++
  * Fixed the friendship problem for old compilers to make the library now gcc 3
    compatible again.
  * Fixed vcprojects/extract_includes.bat to extract compiler/plugin.h.

  Java
  * Removed usages of JDK 1.6 only features to make the library now JDK 1.5
    compatible again.
  * Fixed a bug about negative enum values.
  * serialVersionUID is now defined in generated messages for java serializing.
  * Fixed protoc to use java.lang.Object, which makes "Object" now a valid
    message name again.

  Python
  * Experimental C++ implementation now requires C++ protobuf library installed.
    See the README.txt in the python directory for details.

2011-02-02 version 2.4.0:

  General
  * The RPC (cc|java|py)_generic_services default value is now false instead of
    true.
  * Custom options can have aggregate types. For example,
      message MyOption {
        optional string comment = 1;
        optional string author = 2;
      }
      extend google.protobuf.FieldOptions {
        optional MyOption myoption = 12345;
      }
    This option can now be set as follows:
      message SomeType {
        optional int32 field = 1 [(myoption) = { comment:'x' author:'y' }];
      }

  C++
  * Various speed and code size optimizations.
  * Added a release_foo() method on string and message fields.
  * Fixed gzip_output_stream sub-stream handling.

  Java
  * Builders now maintain sub-builders for sub-messages. Use getFooBuilder() to
    get the builder for the sub-message "foo". This allows you to repeatedly
    modify deeply-nested sub-messages without rebuilding them.
  * Builder.build() no longer invalidates the Builder for generated messages
    (You may continue to modify it and then build another message).
  * Code generator will generate efficient equals() and hashCode()
    implementations if new option java_generate_equals_and_hash is enabled.
    (Otherwise, reflection-based implementations are used.)
  * Generated messages now implement Serializable.
  * Fields with [deprecated=true] will be marked with @Deprecated in Java.
  * Added lazy conversion of UTF-8 encoded strings to String objects to improve
    performance.
  * Various optimizations.
  * Enum value can be accessed directly, instead of calling getNumber() on the
    enum member.
  * For each enum value, an integer constant is also generated with the suffix
    _VALUE.

  Python
  * Added an experimental  C++ implementation for Python messages via a Python
    extension. Implementation type is controlled by an environment variable
    PROTOCOL_BUFFERS_PYTHON_IMPLEMENTATION (valid values: "cpp" and "python")
    The default value is currently "python" but will be changed to "cpp" in
    future release.
  * Improved performance on message instantiation significantly.
    Most of the work on message instantiation is done just once per message
    class, instead of once per message instance.
  * Improved performance on text message parsing.
  * Allow add() to forward keyword arguments to the concrete class.
      E.g. instead of
        item = repeated_field.add()
        item.foo = bar
        item.baz = quux
      You can do:
        repeated_field.add(foo=bar, baz=quux)
  * Added a sort() interface to the BaseContainer.
  * Added an extend() method to repeated composite fields.
  * Added UTF8 debug string support.

2010-01-08 version 2.3.0:

  General
  * Parsers for repeated numeric fields now always accept both packed and
    unpacked input.  The [packed=true] option only affects serializers.
    Therefore, it is possible to switch a field to packed format without
    breaking backwards-compatibility -- as long as all parties are using
    protobuf 2.3.0 or above, at least.
  * The generic RPC service code generated by the C++, Java, and Python
    generators can be disabled via file options:
      option cc_generic_services = false;
      option java_generic_services = false;
      option py_generic_services = false;
    This allows plugins to generate alternative code, possibly specific to some
    particular RPC implementation.

  protoc
  * Now supports a plugin system for code generators.  Plugins can generate
    code for new languages or inject additional code into the output of other
    code generators.  Plugins are just binaries which accept a protocol buffer
    on stdin and write a protocol buffer to stdout, so they may be written in
    any language.  See src/google/protobuf/compiler/plugin.proto.
    **WARNING**:  Plugins are experimental.  The interface may change in a
    future version.
  * If the output location ends in .zip or .jar, protoc will write its output
    to a zip/jar archive instead of a directory.  For example:
      protoc --java_out=myproto_srcs.jar --python_out=myproto.zip myproto.proto
    Currently the archive contents are not compressed, though this could change
    in the future.
  * inf, -inf, and nan can now be used as default values for float and double
    fields.

  C++
  * Various speed and code size optimizations.
  * DynamicMessageFactory is now fully thread-safe.
  * Message::Utf8DebugString() method is like DebugString() but avoids escaping
    UTF-8 bytes.
  * Compiled-in message types can now contain dynamic extensions, through use
    of CodedInputStream::SetExtensionRegistry().
  * Now compiles shared libraries (DLLs) by default on Cygwin and MinGW, to
    match other platforms.  Use --disable-shared to avoid this.

  Java
  * parseDelimitedFrom() and mergeDelimitedFrom() now detect EOF and return
    false/null instead of throwing an exception.
  * Fixed some initialization ordering bugs.
  * Fixes for OpenJDK 7.

  Python
  * 10-25 times faster than 2.2.0, still pure-Python.
  * Calling a mutating method on a sub-message always instantiates the message
    in its parent even if the mutating method doesn't actually mutate anything
    (e.g. parsing from an empty string).
  * Expanded descriptors a bit.

2009-08-11 version 2.2.0:

  C++
  * Lite mode:  The "optimize_for = LITE_RUNTIME" option causes the compiler
    to generate code which only depends libprotobuf-lite, which is much smaller
    than libprotobuf but lacks descriptors, reflection, and some other features.
  * Fixed bug where Message.Swap(Message) was only implemented for
    optimize_for_speed.  Swap now properly implemented in both modes
    (Issue 91).
  * Added RemoveLast and SwapElements(index1, index2) to Reflection
    interface for repeated elements.
  * Added Swap(Message) to Reflection interface.
  * Floating-point literals in generated code that are intended to be
    single-precision now explicitly have 'f' suffix to avoid pedantic warnings
    produced by some compilers.
  * The [deprecated=true] option now causes the C++ code generator to generate
    a GCC-style deprecation annotation (no-op on other compilers).
  * google::protobuf::GetEnumDescriptor<SomeGeneratedEnumType>() returns the
    EnumDescriptor for that type -- useful for templates which cannot call
    SomeGeneratedEnumType_descriptor().
  * Various optimizations and obscure bug fixes.

  Java
  * Lite mode:  The "optimize_for = LITE_RUNTIME" option causes the compiler
    to generate code which only depends libprotobuf-lite, which is much smaller
    than libprotobuf but lacks descriptors, reflection, and some other features.
  * Lots of style cleanups.

  Python
  * Fixed endianness bug with floats and doubles.
  * Text format parsing support.
  * Fix bug with parsing packed repeated fields in embedded messages.
  * Ability to initialize fields by passing keyword args to constructor.
  * Support iterators in extend and __setslice__ for containers.

2009-05-13 version 2.1.0:

  General
  * Repeated fields of primitive types (types other that string, group, and
    nested messages) may now use the option [packed = true] to get a more
    efficient encoding.  In the new encoding, the entire list is written
    as a single byte blob using the "length-delimited" wire type.  Within
    this blob, the individual values are encoded the same way they would
    be normally except without a tag before each value (thus, they are
    tightly "packed").
  * For each field, the generated code contains an integer constant assigned
    to the field number.  For example, the .proto file:
      message Foo { optional int bar_baz = 123; }
    would generate the following constants, all with the integer value 123:
      C++:     Foo::kBarBazFieldNumber
      Java:    Foo.BAR_BAZ_FIELD_NUMBER
      Python:  Foo.BAR_BAZ_FIELD_NUMBER
    Constants are also generated for extensions, with the same naming scheme.
    These constants may be used as switch cases.
  * Updated bundled Google Test to version 1.3.0.  Google Test is now bundled
    in its verbatim form as a nested autoconf package, so you can drop in any
    other version of Google Test if needed.
  * optimize_for = SPEED is now the default, by popular demand.  Use
    optimize_for = CODE_SIZE if code size is more important in your app.
  * It is now an error to define a default value for a repeated field.
    Previously, this was silently ignored (it had no effect on the generated
    code).
  * Fields can now be marked deprecated like:
      optional int32 foo = 1 [deprecated = true];
    Currently this does not have any actual effect, but in the future the code
    generators may generate deprecation annotations in each language.
  * Cross-compiling should now be possible using the --with-protoc option to
    configure.  See README.txt for more info.

  protoc
  * --error_format=msvs option causes errors to be printed in Visual Studio
    format, which should allow them to be clicked on in the build log to go
    directly to the error location.
  * The type name resolver will no longer resolve type names to fields.  For
    example, this now works:
      message Foo {}
      message Bar {
        optional int32 Foo = 1;
        optional Foo baz = 2;
      }
    Previously, the type of "baz" would resolve to "Bar.Foo", and you'd get
    an error because Bar.Foo is a field, not a type.  Now the type of "baz"
    resolves to the message type Foo.  This change is unlikely to make a
    difference to anyone who follows the Protocol Buffers style guide.

  C++
  * Several optimizations, including but not limited to:
    - Serialization, especially to flat arrays, is 10%-50% faster, possibly
      more for small objects.
    - Several descriptor operations which previously required locking no longer
      do.
    - Descriptors are now constructed lazily on first use, rather than at
      process startup time.  This should save memory in programs which do not
      use descriptors or reflection.
    - UnknownFieldSet completely redesigned to be more efficient (especially in
      terms of memory usage).
    - Various optimizations to reduce code size (though the serialization speed
      optimizations increased code size).
  * Message interface has method ParseFromBoundedZeroCopyStream() which parses
    a limited number of bytes from an input stream rather than parsing until
    EOF.
  * GzipInputStream and GzipOutputStream support reading/writing gzip- or
    zlib-compressed streams if zlib is available.
    (google/protobuf/io/gzip_stream.h)
  * DescriptorPool::FindAllExtensions() and corresponding
    DescriptorDatabase::FindAllExtensions() can be used to enumerate all
    extensions of a given type.
  * For each enum type Foo, protoc will generate functions:
      const string& Foo_Name(Foo value);
      bool Foo_Parse(const string& name, Foo* result);
    The former returns the name of the enum constant corresponding to the given
    value while the latter finds the value corresponding to a name.
  * RepeatedField and RepeatedPtrField now have back-insertion iterators.
  * String fields now have setters that take a char* and a size, in addition
    to the existing ones that took char* or const string&.
  * DescriptorPool::AllowUnknownDependencies() may be used to tell
    DescriptorPool to create placeholder descriptors for unknown entities
    referenced in a FileDescriptorProto.  This can allow you to parse a .proto
    file without having access to other .proto files that it imports, for
    example.
  * Updated gtest to latest version.  The gtest package is now included as a
    nested autoconf package, so it should be able to drop new versions into the
    "gtest" subdirectory without modification.

  Java
  * Fixed bug where Message.mergeFrom(Message) failed to merge extensions.
  * Message interface has new method toBuilder() which is equivalent to
    newBuilderForType().mergeFrom(this).
  * All enums now implement the ProtocolMessageEnum interface.
  * Setting a field to null now throws NullPointerException.
  * Fixed tendency for TextFormat's parsing to overflow the stack when
    parsing large string values.  The underlying problem is with Java's
    regex implementation (which unfortunately uses recursive backtracking
    rather than building an NFA).  Worked around by making use of possessive
    quantifiers.
  * Generated service classes now also generate pure interfaces.  For a service
    Foo, Foo.Interface is a pure interface containing all of the service's
    defined methods.  Foo.newReflectiveService() can be called to wrap an
    instance of this interface in a class that implements the generic
    RpcService interface, which provides reflection support that is usually
    needed by RPC server implementations.
  * RPC interfaces now support blocking operation in addition to non-blocking.
    The protocol compiler generates separate blocking and non-blocking stubs
    which operate against separate blocking and non-blocking RPC interfaces.
    RPC implementations will have to implement the new interfaces in order to
    support blocking mode.
  * New I/O methods parseDelimitedFrom(), mergeDelimitedFrom(), and
    writeDelimitedTo() read and write "delimited" messages from/to a stream,
    meaning that the message size precedes the data.  This way, you can write
    multiple messages to a stream without having to worry about delimiting
    them yourself.
  * Throw a more descriptive exception when build() is double-called.
  * Add a method to query whether CodedInputStream is at the end of the input
    stream.
  * Add a method to reset a CodedInputStream's size counter; useful when
    reading many messages with the same stream.
  * equals() and hashCode() now account for unknown fields.

  Python
  * Added slicing support for repeated scalar fields. Added slice retrieval and
    removal of repeated composite fields.
  * Updated RPC interfaces to allow for blocking operation.  A client may
    now pass None for a callback when making an RPC, in which case the
    call will block until the response is received, and the response
    object will be returned directly to the caller.  This interface change
    cannot be used in practice until RPC implementations are updated to
    implement it.
  * Changes to input_stream.py should make protobuf compatible with appengine.

2008-11-25 version 2.0.3:

  protoc
  * Enum values may now have custom options, using syntax similar to field
    options.
  * Fixed bug where .proto files which use custom options but don't actually
    define them (i.e. they import another .proto file defining the options)
    had to explicitly import descriptor.proto.
  * Adjacent string literals in .proto files will now be concatenated, like in
    C.
  * If an input file is a Windows absolute path (e.g. "C:\foo\bar.proto") and
    the import path only contains "." (or contains "." but does not contain
    the file), protoc incorrectly thought that the file was under ".", because
    it thought that the path was relative (since it didn't start with a slash).
    This has been fixed.

  C++
  * Generated message classes now have a Swap() method which efficiently swaps
    the contents of two objects.
  * All message classes now have a SpaceUsed() method which returns an estimate
    of the number of bytes of allocated memory currently owned by the object.
    This is particularly useful when you are reusing a single message object
    to improve performance but want to make sure it doesn't bloat up too large.
  * New method Message::SerializeAsString() returns a string containing the
    serialized data.  May be more convenient than calling
    SerializeToString(string*).
  * In debug mode, log error messages when string-type fields are found to
    contain bytes that are not valid UTF-8.
  * Fixed bug where a message with multiple extension ranges couldn't parse
    extensions.
  * Fixed bug where MergeFrom(const Message&) didn't do anything if invoked on
    a message that contained no fields (but possibly contained extensions).
  * Fixed ShortDebugString() to not be O(n^2).  Durr.
  * Fixed crash in TextFormat parsing if the first token in the input caused a
    tokenization error.
  * Fixed obscure bugs in zero_copy_stream_impl.cc.
  * Added support for HP C++ on Tru64.
  * Only build tests on "make check", not "make".
  * Fixed alignment issue that caused crashes when using DynamicMessage on
    64-bit Sparc machines.
  * Simplify template usage to work with MSVC 2003.
  * Work around GCC 4.3.x x86_64 compiler bug that caused crashes on startup.
    (This affected Fedora 9 in particular.)
  * Now works on "Solaris 10 using recent Sun Studio".

  Java
  * New overload of mergeFrom() which parses a slice of a byte array instead
    of the whole thing.
  * New method ByteString.asReadOnlyByteBuffer() does what it sounds like.
  * Improved performance of isInitialized() when optimizing for code size.

  Python
  * Corrected ListFields() signature in Message base class to match what
    subclasses actually implement.
  * Some minor refactoring.
  * Don't pass self as first argument to superclass constructor (no longer
    allowed in Python 2.6).

2008-09-29 version 2.0.2:

  General
  * License changed from Apache 2.0 to 3-Clause BSD.
  * It is now possible to define custom "options", which are basically
    annotations which may be placed on definitions in a .proto file.
    For example, you might define a field option called "foo" like so:
      import "google/protobuf/descriptor.proto"
      extend google.protobuf.FieldOptions {
        optional string foo = 12345;
      }
    Then you annotate a field using the "foo" option:
      message MyMessage {
        optional int32 some_field = 1 [(foo) = "bar"]
      }
    The value of this option is then visible via the message's
    Descriptor:
      const FieldDescriptor* field =
        MyMessage::descriptor()->FindFieldByName("some_field");
      assert(field->options().GetExtension(foo) == "bar");
    This feature has been implemented and tested in C++ and Java.
    Other languages may or may not need to do extra work to support
    custom options, depending on how they construct descriptors.

  C++
  * Fixed some GCC warnings that only occur when using -pedantic.
  * Improved static initialization code, making ordering more
    predictable among other things.
  * TextFormat will no longer accept messages which contain multiple
    instances of a singular field.  Previously, the latter instance
    would overwrite the former.
  * Now works on systems that don't have hash_map.

  Java
  * Print @Override annotation in generated code where appropriate.

  Python
  * Strings now use the "unicode" type rather than the "str" type.
    String fields may still be assigned ASCII "str" values; they will
    automatically be converted.
  * Adding a property to an object representing a repeated field now
    raises an exception.  For example:
      # No longer works (and never should have).
      message.some_repeated_field.foo = 1

  Windows
  * We now build static libraries rather than DLLs by default on MSVC.
    See vsprojects/readme.txt for more information.

2008-08-15 version 2.0.1:

  protoc
  * New flags --encode and --decode can be used to convert between protobuf text
    format and binary format from the command-line.
  * New flag --descriptor_set_out can be used to write FileDescriptorProtos for
    all parsed files directly into a single output file.  This is particularly
    useful if you wish to parse .proto files from programs written in languages
    other than C++: just run protoc as a background process and have it output
    a FileDescriptorList, then parse that natively.
  * Improved error message when an enum value's name conflicts with another
    symbol defined in the enum type's scope, e.g. if two enum types declared
    in the same scope have values with the same name.  This is disallowed for
    compatibility with C++, but this wasn't clear from the error.
  * Fixed absolute output paths on Windows.
  * Allow trailing slashes in --proto_path mappings.

  C++
  * Reflection objects are now per-class rather than per-instance.  To make this
    possible, the Reflection interface had to be changed such that all methods
    take the Message instance as a parameter.  This change improves performance
    significantly in memory-bandwidth-limited use cases, since it makes the
    message objects smaller.  Note that source-incompatible interface changes
    like this will not be made again after the library leaves beta.
  * Heuristically detect sub-messages when printing unknown fields.
  * Fix static initialization ordering bug that caused crashes at startup when
    compiling on Mac with static linking.
  * Fixed TokenizerTest when compiling with -DNDEBUG on Linux.
  * Fixed incorrect definition of kint32min.
  * Fix bytes type setter to work with byte sequences with embedded NULLs.
  * Other irrelevant tweaks.

  Java
  * Fixed UnknownFieldSet's parsing of varints larger than 32 bits.
  * Fixed TextFormat's parsing of "inf" and "nan".
  * Fixed TextFormat's parsing of comments.
  * Added info to Java POM that will be required when we upload the
    package to a Maven repo.

  Python
  * MergeFrom(message) and CopyFrom(message) are now implemented.
  * SerializeToString() raises an exception if the message is missing required
    fields.
  * Code organization improvements.
  * Fixed doc comments for RpcController and RpcChannel, which had somehow been
    swapped.
  * Fixed text_format_test on Windows where floating-point exponents sometimes
    contain extra zeros.
  * Fix Python service CallMethod() implementation.

  Other
  * Improved readmes.
  * VIM syntax highlighting improvements.

2008-07-07 version 2.0.0:

  * First public release.