Re: problem setting up interlibrary dependencies

["Marcelo E. Magallon" <mmagallo@debian.org>]

On Sun, Jul 13, 2003 at 11:30:43AM -0400, Aaron M. Ucko wrote:

 > Right.  I would moreover like for the GL variant to supersede the
 > non-GL variant when both are installed, since that's what the
 > GL-neutral higher-level libraries will be linking against.

 Let me sketch something for you...

     Package: libvibrant6
     Depends: whatever

     Package: libvibrant6-gl
     Depends: whatever, libgl1
     Provides: libvibrant6
     Replaces: libvibrant6
     Conflicts: libvibrant6

     Package: libvibrant-dev
     Depends: whatever, libvibrant6

     Package: libvibrant-gl-dev
     Depends: whatever, libvibrant6-gl, libgl-dev
     Provides: libvibrant-dev
     Replaces: libvibrant-dev
     Conflicts: libvibrant-dev

 How does this look on the filesystem?

     Package: libvibrant6

        /usr/lib/libvibrant.so.6.0.0
        /usr/lib/libvibrant.so.6 -> libvibrant.so.6.0.0

     Package: libvibrant-dev
        /usr/lib/libvibrant.so -> libvibrant.so.6

     Package: libvibrant6-gl

        /usr/lib/libvibrant.so.6.0.0
        /usr/lib/libvibrant.so.6 -> libvibrant.so.6.0.0

     Package: libvibrant-gl-dev
        /usr/lib/libvibrant.so -> libvibrant.so.6

 The NEEDS of libvibrant6's libvibrant.so.6:

        libc.so.6
        libsomething.so.1
        libanother.so.2

 The NEEDS of libvibrant6-gl's libvibrant.so.6:

        libc.so.6
        libsomething.so.1
        libanother.so.2
        libGL.so.1

 The shlibs for libvibrant6:

        libvibrant 6 libvibrant6

 The shlibs for libvibrant6-gl:

        libvibrant 6 libvibrant6-gl

 Now let's compile something:

     gcc -c doesntneedGL.c
     gcc -o doesntneedGL doesntneedGL.o -lvibrant

 That works with either of the -dev libraries.  The resulting binary
 works with either library.  What about needsGL.c?

     gcc -c needsGL.c
     gcc -o needsGL needsGL.o -lvibrant

 That will work only if libvibrant-gl-dev is installed.  The resulting
 binary will only work if libvibrant6-gl is installed.

 Now there's a package that needs to make sure it won't be compiled with
 the GL variant (for whatever reason):

     Build-Depends: libvibrant-dev
     Build-Conflicts: libvibrant-gl-dev

 Does that satisfy your needs?  Note that I have simply ignored your
 (implicit) request for a solution that let's you install libvibrant6
 and libvibrant6-gl at the same time.  I have also made the assumption
 that libvibrant's API is sane (and ABI likewise).  This solution
 depends on knowledge about the innerworkings of dpkg-shlibdeps _and_
 the GNU linker _and_ the Linux dynamic linker.  Note furthermore that
 there's a certain assumption about upstream not being of the "it's
 binary forwards compatible" persuassion (what happens if upstream
 decides to introduce a new function call but not modify the SONAME --
 hint, think versioned provides).

 Question: does upstream make a distinction at the link-line level if
 the library has or hasn't OpenGL support?  It's important for
 compatibility with other distributions.

 HTH,

 Marcelo