https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80756
--- Comment #5 from joseph at codesourcery dot com <joseph at codesourcery dot com> --- On Mon, 15 May 2017, vincent-gcc at vinc17 dot net wrote: > GCC misses a diagnostic when the fabs() or fma() function is used in an > initializer. For instance, consider: There are pedwarns-if-pedantic for these cases. > Note that <math.h> is not included, so that fabs() and fma() must not be > regarded as special. But even when these functions are regarded as ISO C's > specified ones, the diagnostic should probably still be present (it seems that > the C standard does not make an exception for such functions, unfortunately). The reservations with external linkage in C99/C11 7.1.3#1 are not conditional on whether the corresponding header is included. (Only C90 Amendment 1 had such reservations conditional on inclusion of the corresponding header, for the new functions it added, and that condition would only be relevant with -std=iso9899:199409.)