Re: Avoid gawkextlib as a separate shared library

[Eli Zaretskii]

> Cc: aschorr@telemetry-investments.com, arnold@skeeve.com, bug-gawk@gnu.org
> From: Manuel Collado <mcollado2011@gmail.com>
> Date: Wed, 18 May 2022 23:54:19 +0200
> 
> $ ./configure --prefix=/c/gnu --with-gawk=/c/gnu --with-gawkextlib=/c/gnu

Btw, while looking into this, I found another subtle problem with the
gawk-mpfr's configure script:  when configured like this:

  $ ./configure --prefix=/d/usr --with-gawk=/d/usr --with-gawkextlib=/d/usr

the configure script told me that I don't have GMP installed:

  checking gawkextlib.h usability... yes
  checking gawkextlib.h presence... yes
  checking for gawkextlib.h... yes
  checking for __gmpz_init in -lgmp... no
  configure: error: GMP was not found. Go install GMP 4.1.4 or later from 
http://www.swox.com/gmp and try again.

This happens because the configure script does this:

  # Check whether --with-gmp was given.
  if test "${with_gmp+set}" = set; then :
    withval=$with_gmp;
                  # some platforms use lib64 and others use lib
                  wldfound=0
                  for wldir in "$withval"/lib* ; do
                          if test -d "$wldir"; then
                                  LDFLAGS="-L${wldir} ${LDFLAGS}"
                                  wldfound=1
                          fi
                  done
                  if test "$wldfound" = 0; then
                          LDFLAGS="-L${withval} ${LDFLAGS}"
                  fi
                  if test -d "$withval/include"; then
                          CPPFLAGS="-I${withval}/include ${CPPFLAGS}"
                  else
                          CPPFLAGS="-I${withval} ${CPPFLAGS}"
                  fi


  fi

The loop over all the matches for "$withval"/lib* adds to LDFLAGS
directories that could cause trouble.  In my case, some of the matches
for lib* included old and incompatible libraries, which failed the
link with -lgmp for reasons completely unrelated to GMP itself.

This means that --with-gmp, --with-mpfr, and --with-gawkextlib cannot
be safely given with a value of $prefix, but should instead be
given with the value of $prefix/lib.

One possible fix would be to explicitly check for lib64, but even that
could be problematic, since one could have, say, 32-bit and 64-bit
libraries in 2 separate directories, and the above test could pick up
the wrong one.