[x264-devel] Dynamic linker uses the "versioned" x264 library, not generic

[Elliot Saba]

The names aren't mangled with the version number inside the shared library,
if that's what you mean, and yes, almost all *nix libraries create a
library of the form *libfoo.x.y.dylib* (or *.so*, if you prefer linux) but
they also almost invariably generate a *libfoo.dylib* that is a symlink to
the "versioned" one, along with a *libfoo.x.dylib*, where *x* denotes the
"major" version and *y* denotes the "minor" version.  Most libraries are
setup in such a way that the "major" version preserves the API so that
bugfixes, etc... can be transparently applied to applications without
needing those applications to be relinked, whereas major breaking changes
force a bump up in the major API version number, thus forcing a relink.  My
guess is the dynamic linker is getting confused by the nonstandard naming
convention used by libx264, thinking that the *125* in *libx264.125.dylib* is
a major version number.
-E

On Sun, Oct 7, 2012 at 8:09 AM, Jan Ekström <jeebjp at gmail.com> wrote:

> On 2012/10/07 1:45, Elliot Saba wrote:
> > Hello, all.  I'm here trying to figure out why, on my machine (OSX
> 10.8.2, clang compiler, using Homebrew as a package manager) my dynamic
> linker picks out the "versioned" x264 library, not the generic one.  As I
> am on OSX, this turns out to be *libx264.125.dylib*, as opposed to the
> generic symlink *libx264.dylib*.
> >
> > This is a problem as whenever libx264 gets a version bump, I then have
> to re-link all software that uses libx264.  A real-world example:
> >
> > *$ otool -L `which ffmpeg` | grep x264*
> > */Users/sabae/.homebrew/lib/libx264.125.dylib (compatibility version
> 0.0.0, current version 0.0.0)*
> >
> > No other software on my computer does this, and it's not something
> inherent in the Homebrew method of compiling ffmpeg, because even if I
> download ffmpeg-1.0 source, configure with *--enable-gpl --enable-libx264*
> and *make*, I still end up with an *ffmpeg* executable dynamically linked
> to *libx264.125.dylib*.
> >
> > Thank you,
> > -E
> >
> >
> > _______________________________________________
> > x264-devel mailing list
> > x264-devel at videolan.org
> > http://mailman.videolan.org/listinfo/x264-devel
> Linking to the versioned library is intentional as far as I can tell.
> Every time the API version gets bumped, there is absolutely no guarantee
> that what you were linking will still work (actually, I'm pretty sure it
> will fail because the main API calls are IIRC also "versioned" as well).
> This is not limited to x264, either. Actually, most of the libraries I have
> on the *nix systems I have access to have "versioned" library files.
>
> Jan E
> _______________________________________________
> x264-devel mailing list
> x264-devel at videolan.org
> http://mailman.videolan.org/listinfo/x264-devel
>
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