https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69602
--- Comment #6 from Manuel López-Ibáñez <manu at gcc dot gnu.org> --- (In reply to Jakub Jelinek from comment #5) > Even if we look through macros, I'd actually think we should warn here. I think we should NOT look through macros. The purpose of the warning is to catch mistakes like xxx && !!xxx or 0 < A || A > 0, but if the user writes f() && g() and both functions return the same value, it is clearly not a bug, even if GCC knows that they are the same function. For the purposes of this warning (and probably several others), we should treat macros as variables and functions. Thus, (errno == EAGAIN || errno == EWOULDBLOCK) /* no warning: EAGAIN and EWOULDBLOCK are not the same macro */ (errno == EAGAIN || EAGAIN == errno) /* warn: logical 'or' of the same expressions */ Of course, this is not trivial to implement at the moment (mostly because we don't have locations for macros that expand to constants, thus even finding that something comes from a macro is not possible in most cases).
