Re: [PATCH v2 2/2] feature_test_macros.7: document _TIME_BITS

[Alejandro Colomar <alx.manpages@gmail.com>]

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Hi Sam,

On 10/13/22 20:30, Sam James wrote:
> Reference: https://wiki.gentoo.org/wiki/Project:Toolchain/time64_migration
> Reference: https://sourceware.org/pipermail/libc-alpha/2022-January/134985.html
> Signed-off-by: Sam James <sam@gentoo.org>
> ---
>   man7/feature_test_macros.7 | 13 +++++++++++++
>   1 file changed, 13 insertions(+)
> 
> diff --git a/man7/feature_test_macros.7 b/man7/feature_test_macros.7
> index cdd962f7f..d33041001 100644
> --- a/man7/feature_test_macros.7
> +++ b/man7/feature_test_macros.7
> @@ -412,6 +412,15 @@ large files with only a recompilation being required.)
>   64-bit systems naturally permit file sizes greater than 2 Gigabytes,
>   and on those systems this macro has no effect.
>   .TP
> +.B _TIME_BITS
> +Defining this macro with the value 64
> +changes the width of
> +.BR time_t (3type)
> +to 64-bit which allows handling of timestamps beyond
> +2038. It is closely related to

Please use semantic newlines.  See man-pages(7):

    Use semantic newlines
        In the source of a manual page, new sentences  should  be
        started on new lines, long sentences should be split into
        lines  at  clause breaks (commas, semicolons, colons, and
        so on), and long clauses should be split at phrase bound‐
        aries.  This convention,  sometimes  known  as  "semantic
        newlines",  makes it easier to see the effect of patches,
        which often operate at the level of individual sentences,
        clauses, or phrases.

That is: 's/2038. /2038.\n/'

> +.B _FILE_OFFSET_BITS
> +and depending on implementation, may require it set.

Am I understanding this right?  _FILE_OFFSET_BITS is required to be set 
for _TIME_BITS to be also set (in some archs)?  Could you please link 
directly to a source for that in the commit log?  They are somewhat 
related, but I'm quite surprised that something to do with file sizes 
interferes at all with something to do with time.

Thanks,

Alex

> +.TP
>   .BR _BSD_SOURCE " (deprecated since glibc 2.20)"
>   Defining this macro with any value causes header files to expose
>   BSD-derived definitions.
> @@ -854,6 +863,10 @@ main(int argc, char *argv[])
>       printf("_FILE_OFFSET_BITS defined: %d\en", _FILE_OFFSET_BITS);
>   #endif
>   
> +#ifdef _TIME_BITS
> +    printf("_TIME_BITS defined: %d\en", _TIME_BITS);
> +#endif
> +
>   #ifdef _BSD_SOURCE
>       printf("_BSD_SOURCE defined\en");
>   #endif

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

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