Re: libgmp: link to the correct shared library

[Paul Eggert]

On 7/23/20 3:30 PM, Bruno Haible wrote:

> If, say, we change the 'factor' program in GNU coreutils
> to use GMP, so that it can factor integers with more than 20 digits, anyone who
> wants to use their own installed GMP would get programs (from 'expr' to 'mkdir')
> that all spend time, during program startup, to look up their libraries in
> /PREFIX64/lib.
This may not be perfect, but it's good enough for many applications. Coreutils 
has been doing it this way since Coreutils 7.0 (2008) and it doesn't appear to 
have been a significant problem in practice. (Plus, Coreutils 'expr' already 
links to GMP anyway. :-)

> Also, adding -Wl,-rpath=/PREFIX64/lib to LDFLAGS will have ill consequences
> when the package contains shared libraries and uses libtool to create them. See
> <https://lists.gnu.org/archive/html/bug-gnulib/2020-05/msg00102.html>.

That's OK too, since Emacs and coreutils don't use libtool to create packages.

> Do you think there is something to add to the documentation
> https://www.gnu.org/software/gnulib/manual/html_node/Searching-for-Libraries.html
>  ?

I am hoping that I do not have to read that documentation; I just want to keep 
building Coreutils the way it's been built for quite some time. I introduced 
libgmp in order make it easier to use GMP in other apps like Emacs; I didn't 
want the module to complicate configuration in coreutils or in other packages 
that don't need the complication. Emacs in particular prefers to use pkg-config 
and PKG_CHECK_MODULES to configure libraries, and I don't want to have to worry 
about how that interacts with libtool.

I'm not saying I'm against having a libtool-aware GMP module in Gnulib; I merely 
want to be able to use GMP without worrying about libtool.