[FFmpeg-devel] [PATCH 3/3] configure: Remove -Wredundant-decls on OS/2 to suppress noise.

KO Myung-Hun komh78 at gmail.com
Thu Apr 28 14:13:21 CEST 2016

Dmitriy Kuminov wrote:
> On 2016-04-21 06:46:38 +0000, Reimar Döffinger said:
>> Have something that results in adding -I/usr/include to the compile
>> options or to C_INCLUDE_PATH? Probably your compiler is misconfigured
>> to not consider that a system include path.
>> Adding -isystem /usr/include should fix it.
> I finally had some time to research. No, our compiler (at least the RPM
> releases from BWW) is not misconfigured, /@unixroot/usr/include is the
> system include path and a simple `gcc -Zomf -Wredundant-decls -c
> hello.c` works well. However, when building FFmpeg stuff,
> -I/@unxroot/usr/include indeed ends up in CFLAGS multiple times and all
> these come from .pc files (namely, fontconfig.pc and vpx.pc). And from
> what I see in the sources, -I${includedir} a very common thing which is
> often used in Cflags: in .pc.in, including fontconfig.pc.in (and
> {includedir} is normally /usr/include or such). So all other platforms
> should be suffering from -Wredundant-decls as well (unless their libc
> headers are very clean and don't contain duplicate decls).

Then, it may be a problem of pkg-config. pkg-config does not output
system header directories such as /usr/include unless
PKG_CONFIG_ALLOW_SYSTEM_CFLAGS is set. However, pkg-config seems not to
think of /@unixroot/usr/include as a system header directory.

As a result, the correct way is to fix pkg-config itself to understand
/@unixroot notation. Or remove /@unixroot prefix from .pc files as a

> So unless I miss something else, we should still apply this patch (as
> fixing OS/2 libc headers won't happen any time soon).

KO Myung-Hun

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