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Message-ID: <54119475.1090208@posteo.de>
Date: Thu, 11 Sep 2014 14:24:21 +0200
From: Jörg Krause <jkrause@...teo.de>
To: musl@...ts.openwall.com
Subject: Re: why is there no __MUSL__ macro?
On 09/11/2014 01:17 PM, Jens wrote:
>
> On Thu, 11 Sep 2014, Jörg Krause wrote:
>> Hi,
>>
>> I am trying to add support for the musl toolchain to FFmpeg.
>>
>> FFmpeg needs support for library features defined in POSIX.1-2001
>> with XSI extension and the standards
>> below. Currently configure probes the host and target libc by
>> checking for defined macros like __GLIBC__ and
>> __UCLIBC__. In case of glibc and uclibc it sets -D_XOPEN_SOURCE=600
>> properly.
>>
>> After this it checks for some combinations of hardware and the probed
>> libc to set some more compile options,
>> if necessary.
>>
>> I know that musl does not have a macro __MUSL__ and I have read the
>> explanation. However, I don't understand
>> what's meant by "[..] it's a bug to assume a certain implementation
>> has particular properties rather than
>> testing." and how does it affect the way FFmpeg probes for the libc.
>
> Maybe the explanation in the FAQ could be a bit more verbose.
Maybe that would help :-)
> But if you stop and think for a bit you'll realize that __MUSL__ would
> tell you next to nothing. musl and any other libc that is maintained
> will change with time. You cannot assume a specific functionality by
> checking for __MUSL__. Bugs will be fixed, functionality will be
> implemented etc.
I see.
>
> Even if you could check for a specific version of musl you will do
> most people a disservice since their libc/version wont be handled.
> If instead you check for a specific functionality, it will be
> independent of libc and version of libc.
I am not sure what you mean with "check for a specific functionality"?
>
> A somewhat limited build of ffmpeg, atleast, works fine with musl:
> OPTPREFIX=opt/av
> configure --prefix=/$OPTPREFIX \
> --enable-gpl\
> --enable-small --disable-ffplay --disable-ffprobe --disable-ffserver\
> --enable-libmp3lame\
> --enable-libx264 \
> --disable-network --cc=musl-gcc
I'm using a musl cross-compiling toolchain and the limited build even
without mp3 and x264 fails for me:
./configure --enable-cross-compile\
--cross-prefix=/home/joerg/x86_64-linux-musl/bin/x86_64-linux-musl-\
--arch=x86_64 --target-os=linux\
--prefix=/home/joerg/test/ffmpeg\
--enable-gpl\
--enable-small --disable-ffplay --disable-ffprobe --disable-ffserver\
--disable-network
[...]
make: *** [libavformat/segment.o] Error 1
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