Re: git: 8d29d2429649 - main - libc: Restore prior C23 include guards

Devin Teske <dteske@freebsd.org> writes:
> If someone uses __STDC_VERSION_*_H__ to inject C23 syntax of their
> own, they are asking the advertisement to do visibility's job.  I may
> be missing a case where that is the right test; I have not found it in
> 7.1.2p6 yet.

Imagine a single-header library (i.e. a big collection of static inline
functions) that uses __STDC_VERSION_FOO_H__ to choose between a C23
solution and a backward-compatible solution.  This header is then
included in a C99 program and fails because we are advertising C23
features to a C99 program.  It's really not that hard to understand.

> Your predicate (__ISO_C_VISIBLE >= 2023 || __BSD_VISIBLE) would make
> the macros mean "this compilation can see C23 semantics from this
> header."  That is a policy we can talk about on its own.  I would
> rather not fold it into the _FOO_H_ restore, which was only POLA after
> gmp.

I don't know what you mean with “fold it into the _FOO_H_ restore”.  The
“_FOO_H_ restore” has already happened and we're not going to rewrite
history.  I am asking for this feature to be implemented correctly.

DES
-- 
Dag-Erling Smørgrav - des@FreeBSD.org