On 8/11/14, Andreas Cadhalpun <andreas.cadhal...@googlemail.com> wrote: > Hi Ivan, > > On 11.08.2014 01:23, Ivan Kalvachev wrote: >> The patch is inspired by something I read in the Debian discussion. >> Libav and FFmpeg could be installed side by side without conflicts in >> the libraries, thanks to using additional suffixes. > > Thanks for your interest in the matter. > >> However development/include files are still conflicting, so I thought >> of a simple configure hack to give more control to FFmpeg. >> >> With this patch you can do `./configure --extra-incdir="/ffmpeg" >> --prefix="/usr"` , >> as result the header files would be installed in >> "/usr/include/ffmpeg" >> e.g. >> "/usr/include/ffmpeg/libavcodec/avcodec.h" >> ... > > Assuming it would be possible to install development packages for both > at the same time, which one should be used, when building a program?
It would be decided by the gcc -I inclusion option. It modifies the search paths for header files, so that it checks these paths before the system/default ones (When using `#include "libavcodec/avcodec.h" `) Libav headers are probably going to remain in the default /usr/include/ . Usually this should not be a problem, unless a program uses `#include <libavcodec/avcodec.h> ` that should be used for system headers (aka checks the system/default paths first). There might still be problems if there are explicit -I/usr/include inserted by other libraries that mix the inclusion order. To avoid hard to debug compiling problems, that the -dev packages may still be marked as conflicting, even though no files are overwritten. This final conflict however cannot be resolved on FFmpeg side. >> The change is reflected in the pkgconfig files too. Since applications >> that link to libraries with addition suffixes should be using >> pkgconfig, they would be using the correct header includes >> automatically. > > If that's to be determined via pkg-config files, then the obvious > problem is that both install these files in the same location, and if > one doesn't, programs can't find the library. The problem is not that they are installed in the same location, but that they have same names. However I just checked and when you define library suffix (e.g. --build-suffix="_ffmpeg"), it also adds the same suffix to the .pc files. So you have /usr/lib/share/pkgconfig/libavcodec_ffmpeg.pc /usr/lib/libavcodec_ffmpeg.so In short, assuming if Libav doesn't change their library names and pkgconfig files, the programs that are looking for 'libavcodec.pc' would get the Libav one, the programs that are looking for 'libavcodec_ffmpeg.pc' would get FFmpeg. I believe that you should already be using --build-suffix, so that should already be in the package. Is there something else I'm missing? >> I did just a rudimentary test and I couldn't spot anything wrong. >> Please test it before inclusion. > > The patch seems to be alright, but it doesn't make it possible to make > the development packages of FFmpeg and Libav co-installable. Unfortunately not. But without the patch the problem is entirely in how FFmpeg installs its header. With it, it is entirely Libav problem for using system/common directory. Then, if Debian wants to resolve the conflict, Libav header files could be moved in their own directory. The patch should be trivial to port. >> As for the future, it might be good idea next major release (e.g. 3.0) >> to have the $prefix/include/ffmpeg as default include path (for >> non-comapt build). > > So this would also not help. At the moment FFmpeg is trying to mimic 100% Libav API/ABI, and to be perfect drop-in replacement. This means using the same library names, locations and header files. This is what I call compat build. It is 100% compatible with Libav from application/program point of view. When using --build-suffix, you obviously want to differentiate from Libav, so I call that non-compat build. Sorry if this is caused confusion. I hope that the way Debian packages FFmpeg would actually turn out to be the new default. Best Regards Ivan Kalvachev iive _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
