On Sat, 13 Jun 2026, Alejandro Colomar via Gcc wrote:
> I was reviewing the feature_test_macros(7) page, and found the
> documentation of the _ISOC{99,11,23,...}_SOURCE macros to be incorrect.
> And thinking about fixing that led me to think that the design of those
> macros is less than ideal.
Users should normally use -std= options with the compiler to get matching
language and library features. These feature test macros are mainly for
niche cases with old compilers. So I don't think any new user-facing
design for them should be added (the C23 and later ones already use the
newer __GLIBC_USE style of conditionals in the header implementation).
--
Joseph S. Myers
[email protected]
