[Bug c/80756] missing diagnostic on non-constant expression with function call such as fabs or fma in initializer

[joseph at codesourcery dot com]

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.)