https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69602
--- Comment #16 from Martin Sebor <msebor at gcc dot gnu.org> --- There are straightforward ways to avoid interspersing code with preprocessor conditionals: #if EAGAIN == EWOULDBLOCK # #define EAGAIN_OR_WOULDBLOCK(e) (e == EAGAIN) #else # #define EAGAIN_OR_WOULDBLOCK(e) (e == EAGAIN || e == EWOULDBLOCK) #endif ... if (cchRead < 0 && EAGAIN_OR_WOULDBLOCK (errno)) The point is that the warning is simple and works as designed. As others have noted, handling this case is non-trivial and as with any non-trivial solution could easily have unforeseen side-effects and even lead to bugs (at a minimum, likely false negatives). I ended up here because I've been researching just such a problem. So unless the idiom in comment #0 is pervasive and leads to many warnings I would suggest to leave it to programs to deal with. Marek and Jakub will likely have an idea of how common it is once they rebuild Fedora with GCC 7. If you have data of your own that might be helpful as well.
