Update libc++ to 1 May 2022 639b9618f46d75f4dabd2082b3f6ba8433c287bf

1 files changed, 20 insertions, 7 deletions

diff --git a/contrib/libs/cxxsupp/libcxx/include/fstream b/contrib/libs/cxxsupp/libcxx/include/fstream
index 907c59e888..7608daa3f9 100644
--- a/contrib/libs/cxxsupp/libcxx/include/fstream
+++ b/contrib/libs/cxxsupp/libcxx/include/fstream
@@ -419,25 +419,38 @@ basic_filebuf<_CharT, _Traits>::swap(basic_filebuf& __rhs)
     basic_streambuf<char_type, traits_type>::swap(__rhs);
     if (__extbuf_ != __extbuf_min_ && __rhs.__extbuf_ != __rhs.__extbuf_min_)
     {
-        _VSTD::swap(__extbuf_, __rhs.__extbuf_);
-        _VSTD::swap(__extbufnext_, __rhs.__extbufnext_);
-        _VSTD::swap(__extbufend_, __rhs.__extbufend_);
+        // Neither *this nor __rhs uses the small buffer, so we can simply swap the pointers.
+        std::swap(__extbuf_, __rhs.__extbuf_);
+        std::swap(__extbufnext_, __rhs.__extbufnext_);
+        std::swap(__extbufend_, __rhs.__extbufend_);
     }
     else
     {
-        ptrdiff_t __ln = __extbufnext_ - __extbuf_;
-        ptrdiff_t __le = __extbufend_ - __extbuf_;
-        ptrdiff_t __rn = __rhs.__extbufnext_ - __rhs.__extbuf_;
-        ptrdiff_t __re = __rhs.__extbufend_ - __rhs.__extbuf_;
+        ptrdiff_t __ln = __extbufnext_       ? __extbufnext_ - __extbuf_             : 0;
+        ptrdiff_t __le = __extbufend_        ? __extbufend_ - __extbuf_              : 0;
+        ptrdiff_t __rn = __rhs.__extbufnext_ ? __rhs.__extbufnext_ - __rhs.__extbuf_ : 0;
+        ptrdiff_t __re = __rhs.__extbufend_  ? __rhs.__extbufend_ - __rhs.__extbuf_  : 0;
         if (__extbuf_ == __extbuf_min_ && __rhs.__extbuf_ != __rhs.__extbuf_min_)
         {
+            // *this uses the small buffer, but __rhs doesn't.
             __extbuf_ = __rhs.__extbuf_;
             __rhs.__extbuf_ = __rhs.__extbuf_min_;
+            std::memmove(__rhs.__extbuf_min_, __extbuf_min_, sizeof(__extbuf_min_));
         }
         else if (__extbuf_ != __extbuf_min_ && __rhs.__extbuf_ == __rhs.__extbuf_min_)
         {
+            // *this doesn't use the small buffer, but __rhs does.
             __rhs.__extbuf_ = __extbuf_;
             __extbuf_ = __extbuf_min_;
+            std::memmove(__extbuf_min_, __rhs.__extbuf_min_, sizeof(__extbuf_min_));
+        }
+        else
+        {
+            // Both *this and __rhs use the small buffer.
+            char __tmp[sizeof(__extbuf_min_)];
+            std::memmove(__tmp, __extbuf_min_, sizeof(__extbuf_min_));
+            std::memmove(__extbuf_min_, __rhs.__extbuf_min_, sizeof(__extbuf_min_));
+            std::memmove(__rhs.__extbuf_min_, __tmp, sizeof(__extbuf_min_));
         }
         __extbufnext_ = __extbuf_ + __rn;
         __extbufend_ = __extbuf_ + __re;