[FFmpeg-devel] [PATCH]Allow libspeex detection also without pkg-config

[Clément Bœsch]

On Wed, Dec 31, 2014 at 02:57:43PM +0100, Reimar Döffinger wrote:
> On Wed, Dec 31, 2014 at 02:38:20PM +0100, Clément Bœsch wrote:
> > On Wed, Dec 31, 2014 at 02:23:54PM +0100, Reimar Döffinger wrote:
> > > On Wed, Dec 31, 2014 at 02:09:42PM +0100, Nicolas George wrote:
> > > > Le primidi 11 nivôse, an CCXXIII, Reimar Döffinger a écrit :
> > > > > I don't care much, but I still find not having to use pkg-config
> > > > > somewhat more convenient in a cross-compilation environment where
> > > > > you don't want to install all dependencies just to make it work with
> > > > > pkg-config (or alternatively manually hack those files).
> > > > 
> > > > Can you elaborate on that? I suspect there are ways of making this work
> > > > easily with pkg-config, but you are to vague about the dependencies you want
> > > > to avoid, so I can not suggest a way.
> > > 
> > > If I just download libspeex, libfdk_aac, libsdl etc. and build them
> > > with CC=i686-mingw32-gcc ./configure, then without pkg-config I can
> > > just add a few paths to -I and -L and I can link against them.
> > > With pkg-config things tend to get inconsistent and more complicated.
> > > For example some programs (no, I haven't tried lately so I don't
> > > remember examples) generate them only on install, so you have to
> > > make install. But to do that you have to figure out how to specify
> > > a install directory.
> > 
> > The .pc files are obviously generally generated because the library they
> > depend on (for static stuff) depends on your configure options, so
> > obviously that's what you want: flags automatically added that way.
> 
> The problem isn't them being generated.
> The problem is if it is only "make install" that generates them.
> 

How is that really a problem? You can just ./configure
--prefix=$PWD/install (or wherever you fancy) from the library source
directory

> > > Even if they don't, you still have to add the .pc paths in addition.
> > > From my point of view it's only more convenient if all you want to
> > > use are things that are pre-packaged by your distribution.
> > > Btw. would you be less opposed to a patch that added less obfuscation?
> > 
> > > It looks to me like we would just require an extra "fallback -l" option
> > > (preferably also a fallback extra cflags one) to use_pkg_config to allow
> > > hiding all the extra complexity in one place, inside that function.
> > 
> > The problem is that the fallback is really broken. pkg-config has a
> > mechanism to check for version, it also has a mechanism to raise different
> > flags depending on the build, and it also has a system to differenciate
> > the flags necessary for static or dynamic building.
> > 
> > Look at the current multiline and unreliable (no pkg-config + x264 with
> > opencl will badly break)
> 
> That is not obvious to me, why would it badly break?
> If it does, doesn't that mean require_pkg_config will break the same
> way if your .pc happens to be from a non-opencl x264 by mistake,
> and thus it would be better to fix anyway?
> 

You're supposed to have your .pc file in $PREFIX/lib/pkgconfig/x264.pc
along with $PREFIX/lib/x264.pc

You obviously need to make pkg-config point on the appropriate directory
if it's in a special place (with PKG_CONFIG_PATH). And this process is
widely documented.

> > And if the user doesn't have pkg-config, an explicit error is raise: "you
> > must install pkg-config", which is simpler to solve than a weird linkage
> > error on opencl in the config.log and an error saying "i can't find x264"
> 
> It's not necessarily easier to solve when users end up with broken .pc files.
> Which happens easily if they e.g. have a system x264.pc file and try to
> use a locally compiled one (with OpenCL enabled for example).
> If we don't have a reliable detection, these issues will happen even
> with pkg-config.
> And if we have a reliable detection, except for the complexity we need
> to handle I don't see a big issue with making a least-effort attempt
> without pkg-config.

-- 
Clément B.
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