Re: [PATCH] Remove any mention of feature test macro requirements for mmap()

Re: [PATCH] Remove any mention of feature test macro requirements for mmap()

[Alejandro Colomar]

[-- Attachment #1.1: Type: text/plain, Size: 2472 bytes --]

Hi John, Andreas,

On 10/19/22 14:25, John Scott wrote:
> I'm not subscribed, please CC me.
> 
> glibc doesn't require_GNU_SOURCE to expose certain MAP_* constants
> anymore (MAP_ANONYMOUS being particularly noteworthy among them for
> being on track for POSIX Issue 8). See this commit:
> https://sourceware.org/git/?p=glibc.git;a=commit;h=954b8f38958de72c4712088735eb175118f17b51
> 
> or my glibc bug report which triggered the change at
> https://sourceware.org/bugzilla/show_bug.cgi?id=29375
> 
> This is because POSIX reserves MAP_ constants to the implementation, so
> their unconditional visibility in sys/mman.h is always allowed. This is
> also helpful for portable application writers.
> 
> Other C libraries like musl already exhibit this behavior.
> 
> Because mmap() is in a POSIX-specific header already, using it with any
> combination of MAP_ constants doesn't require feature test macros.
> 
> Thanks for your consideration
> 
> 
> 0001-Remove-any-feature-test-macro-requirements-for-mmap.patch
> 
>  From 47632888627cac3d0547a969c55d3848b3b350b7 Mon Sep 17 00:00:00 2001
> From: John Scott<jscott@posteo.net>
> Date: Wed, 19 Oct 2022 06:25:25 -0400
> Subject: [PATCH] Remove any feature test macro requirements for mmap()
> 
> No feature test macros are required anymore, not even
> to expose certain constants. See
> https://sourceware.org/bugzilla/show_bug.cgi?id=29375
> ---
>   man2/mmap.2 | 35 -----------------------------------
>   1 file changed, 35 deletions(-)
> 
> diff --git a/man2/mmap.2 b/man2/mmap.2
> index 9c343f2..8a2bddf 100644
> --- a/man2/mmap.2
> +++ b/man2/mmap.2
> @@ -32,8 +32,6 @@ Standard C library
>   .BI "           int " fd ", off_t " offset );
>   .BI "int munmap(void *" addr ", size_t " length );
>   .fi
> -.PP
> -See NOTES for information on feature test macro requirements.
>   .SH DESCRIPTION
>   .BR mmap ()
>   creates a new mapping in the virtual address space of
> @@ -727,39 +725,6 @@ flag is specified, and
>   .I addr
>   is 0 (NULL), then the mapped address will be 0 (NULL).
>   .PP
> -Certain
> -.I flags
> -constants are defined only if suitable feature test macros are defined
> -(possibly by default):
> -.B _DEFAULT_SOURCE
> -with glibc 2.19 or later;

We should keep some notice that in the past it was needed.  BTW, is 
glibc backporting the fix to old supported versions?

Thanks,

Alex

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

[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 833 bytes --]