Gerald Pfeifer gerald@pfeifer.com writes:
On Wed, 16 Apr 2014, Paul Chitescu wrote:
Digging into this in more detail I see
../msvcp90/ios.c: In function 'basic_streambuf_char__Xsgetn_s': ../msvcp90/msvcp90.h:529:75: warning: right-hand operand of comma expression has no effect [-Wunused-value] #define memcpy_s( dst, size, src, count ) (memcpy( (dst), (src), (count) ), 0) ^ ../msvcp90/ios.c:1218:13: note: in expansion of macro 'memcpy_s' memcpy_s(ptr+copied, size, *this->prpos, chunk); ^
memcpy_s() returns an errno_t so the author tried to force returning zero (no error).
Since, clearly, the result is never intended to be used, we can as well simply cast the result away instead of using ", 0".
memcpy_s is supposed to return a value, and callers could (and probably should) check it.