Best practice for extracting information from a makefile

[Michael Schwendt]

On Tue, 16 Aug 2011 10:38:43 -0500, RS (Richard) wrote:

> > cd %{buildroot}%{libdir}
> > ldconfig -n $(pwd)
> > ln -s %{name}.so.? %{name}.so
> > cd -
> 
> Wouldn't that create a symlink of a symlink?

That isn't a problem, is it? All that matters is that the final symlink would
point at a usable library the build-time linker can load

  libfoo.so -> libfoo.so.1 > libfoo.so.1.0.0

and ldconfig adjusts libfoo.so.1 to point at the latest version anyway.
Or just the direct:

  libfoo.so -> libfoo.so.1.0.0

Both types of symlinks exist in Fedora packages.
You could

  shopt -s failglob
  ln -s %{name}.so.*.* %{name}.so

enforcing existence of a fully versioned library, and else an error.
All that matters is that the final symlink would point at a usable
library.

> I ended up doing it this way:
> 
> # Extract library name from Makefile
> LIBNAME=$(make -f Makefile -f - <<<'lib_so:; @echo $(lib_so)' lib_so)
> 
> # Create symbolic link for -devel subpackage.
> ldconfig -n %{buildroot}%{_libdir}
> pushd %{buildroot}%{_libdir}
> ln -s $LIBNAME %{name}.so
> popd

Enjoy it if it works for you. :)
Note though that if the make command fails, you would end up with an
empty $LIBNAME and a  %{name}.so -> %{name}.so  most likely, so some guard
in the spec file would be beneficial.