Re: _ISOCxx_SOURCE

Alejandro Colomar <[email protected]> Mon, 15 Jun 2026 23:06:44 +0200

Newsgroups	org.kernel.vger.linux-man
Message-ID	<ajBpIbEH_7KkJrld@devuan>

Hi Joseph,

On 2026-06-15T17:20:17+0000, Joseph Myers wrote:
> 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).

Makes sense.  Should I document that users should avoid setting them
directly (and that they should use the corresponding compiler flag)?


Have a lovely night!
Alex

-- 
<https://www.alejandro-colomar.es>

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