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author | Andreas Rheinhardt <andreas.rheinhardt@outlook.com> | 2022-05-13 00:16:30 +0200 |
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committer | Andreas Rheinhardt <andreas.rheinhardt@outlook.com> | 2022-05-24 21:30:52 +0200 |
commit | a78173374a897e659b16a53b0a04a7ed550a0e32 (patch) | |
tree | 87bd14bb5c995d2a3939772338a08d0488d90eaf /libavfilter/vf_vidstabdetect.c | |
parent | b033913d1c5998a29dfd13e9906dd707ff6eff12 (diff) | |
download | ffmpeg-a78173374a897e659b16a53b0a04a7ed550a0e32.tar.gz |
ffbuild/common: Fix CPPFLAGS applied for compiling C++ files
Currently, $(CPPFLAGS) and $(CFLAGS) are prepended to CXXFLAGS
(the flags for compiling C++) like this:
CXXFLAGS := $(CPPFLAGS) $(CFLAGS) $(CXXFLAGS)
Using ":=" creates a simply expanded variable, i.e. the values
of the variable at the time of assignment are used and later
modifications to them are ignored (using a recursively expanding
variable (i.e. "=" instead of ":=") is not really possible here,
as there would be an infinite loop when evaluating CXXFLAGS).
Yet we perform later additions to CPPFLAGS: HAVE_AV_CONFIG_H and
BUILDING_libfoo are defined. These do not reach C++ compilations.
To fix this a trick is employed to prepend to a recursively
expanded variable while keeping it recursively expanded.
There are two practical consequences of this: C++ files now no longer
include the version.h header, but only the version_major.h header
of their library, saving some recompilations. Furthermore, they
now get some optimized math functions (namely the ones from
lavu/intmath.h instead of the ones from lavu/common.h).
(av_parity() is the only one for which it makes a difference.)
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
Diffstat (limited to 'libavfilter/vf_vidstabdetect.c')
0 files changed, 0 insertions, 0 deletions