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Re: Build failure with GCC 15 (defaults to -std=gnu23)

Thomas Munro <thomas.munro@gmail.com>

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From: Thomas Munro <thomas.munro@gmail.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Sam James <sam@gentoo.org>, pgsql-bugs@lists.postgresql.org
Date: 2024-11-17T19:30:56Z
Lists: pgsql-bugs 
On Mon, Nov 18, 2024 at 7:12 AM Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Sam James <sam@gentoo.org> writes:
> > postgres-17.1 fails to build with upcoming GCC 15 which defaults to
> > -std=gnu23 as follows:
>
> I do not think we claim to support C23 yet.
>
> Having said that, I can reproduce this on gcc 14 using -std=gnu23.
> It appears that configure is deciding that <stdbool.h> is not
> conformant to C99 because it doesn't declare "bool" as a macro.
> Did C23 really remove that !?

Yes, seems to be a general pattern: features introduced as keyword
_Xxx with a library macro xxx -> _Xxx (usually where xxx is already a
keyword in C++ but the C committee was afraid to unleash a new keyword
directly on the world, I guess?), and now xxx is finally graduating to
real keyword status.  Other examples: static_assert, thread_local,
alignas.

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Require sizeof(bool) == 1.

  2. If a C23 compiler is detected, try asking for C17.

  3. Fix C23 compiler warning

  4. Rename C23 keyword

  5. Assume that <stdbool.h> conforms to the C standard.

  6. Revise tree-walk APIs to improve spec compliance & silence warnings.