[FFmpeg-devel] [PATCH v2 1/1] configure: Refactor setting of feature test macro _XOPEN_SOURCE

Michael Niedermayer michaelni at gmx.at
Thu Sep 18 17:26:05 CEST 2014

On Thu, Sep 18, 2014 at 04:22:27PM +0200, Jörg Krause wrote:
> glibc, uclibc, and musl uses feature test macros to expose definitions 
> conforming to the standards ISO C, POSIX and extensions. According to
> which feature test macros are defined by the user or the compiler, 
> the header file <features.h> used by these libraries internally defines
> various other macros.
> glibc and uclibc also defines release test macros, eg __GLIBC__ and
> __UCLIBC__ in <features.h>. musl does not have (and do not want) such 
> a macro like __MUSL__. 
> Building ffmpeg with the musl toolchain needs the feature test macro
> _XOPEN_SOURCE=600 to be defined. As it is not possible to detect musl  
> check for the <features.h> header file, which is assumed to be specific 
> to glibc, uclibc, and musl. 
> Signed-off-by: Jörg Krause <jkrause at posteo.de>
> ---
> Changes  v1 -> v2:
>   - do not set _XOPEN_SOURCE twice for glibc and uclibc

why do you not add the musl check at the end of the if/elif chain as
suggested ?
does that have some issue or problem ?

now your patch removes POSIX_C_SOURCE=200112 for glibc & uclibc
maybe thats ok, maybe its not but it certainly doesnt belong in a
patch that adds musl support
If you think this change is desireable, please submit a seperate

also seperating the existing checks between a group which has
features.h and one that does not, would need someone to check if thats
correct for each
if any thats in the "no features.h" group has a header with the name
features.h then it would break

and the patch also breaks mingw cross compile

i get

> +        elif check_${pfx}cpp_condition features.h "defined __GLIBC__"; then
> +            eval ${pfx}libc_type=glibc
> +    fi

the "fi" is misleadingly indented or rather not indented

Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

It is dangerous to be right in matters on which the established authorities
are wrong. -- Voltaire
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