Introduce I_STDCKDINT config macro to indicate <stdckdint.h> availability

[t-a-k]

This patch will define I_STDCKDINT macro in config.h if C23 <stdckdint.h> is available.

This will complement the recently merged patch (0f2b1e6, GH #23503) to make the new code available to C23-compliant compilers, not only to GCC-compatible ones.

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• This set of changes requires a perldelta entry, and it is included.

[sisyphus]

Looks good to me, on 32-bit and 64-bit gcc-15.2.0 builds on Windows 11.
A default build of Windows will specify the -std=c99 switch as part of ccflags - so I guess that will prevent most Windows users from defining I_STDCKDINT (in win32/config_H.gc) and i_stdckdint (in win32/config.c).

I build my windows perls without that repressive switch, so I get a perl built at the same level as the compiler's default (which is C23 in this case).
Perl's test suite passes all tests.
perl -V:i_stdckdint reports "defined", and I ran an Inline::C script that confirmed that the I_STDCKDINT symbol is defined at the XS level.

That's about it. Is there some other aspect that I should be looking at ?

[sisyphus]

A default build of Windows will specify the -std=c99 switch as part of ccflags - so I guess that will prevent most Windows users from defining I_STDCKDINT (in win32/config_H.gc) and i_stdckdint (in win32/config.c).

No - I was wrong about that. A Windows perl built with gcc-15 can still access stdckint.h even if the C level is set to C99, so long as win32/config_H.gc and win32/config.gc have been edited to include the relevant definitions.

[t-a-k]

@sisyphus Thank you for comments.
I think that config.gc's i_stdckdint should be undef as README.win32 seems to say that minimum supported GCC version is 3.4.5 which don't have <stdckdint.h>. config_sh.PL could be modified to tweak this depending on detected GCC version, but unfortunately I don't have Win32 test environment.

[sisyphus]

On Thu, Sep 18, 2025 at 4:33 AM TAKAI Kousuke ***@***.***> wrote: *t-a-k* left a comment (Perl/perl5#23703) <#23703 (comment)> @sisyphus <https://github.com/sisyphus> Thank you for comments. I think that config.gc's i_stdckdint should be undef as README.win32 <http://../blob/blead/README.win32> seems to say that minimum supported GCC version is 3.4.5 which don't have <stdckdint.h>. config_sh.PL could be modified to tweak this depending on detected GCC version, but unfortunately I don't have Win32 test environment.

Yes, having config_sh.PL deal with this is the correct solution. For now, it was just easier for me to manually edit config.gc and config_H.gc - but I'll work on implementing the option properly with the devel release of 5.43.3, and submit a PR when I've got it functioning correctly.