Bug in libtool

[Carlo Wood]

As a developer of C++ libraries, I need to have multiple
versions of g++ installed, in order to test if my libraries
work with each of them.

These compilers are simply configured with a different
prefix and installed.  My default compiler is redhat 2.96
and resides in prefix /usr.  All other versions have
prefix /usr/local/gcc-VERSION.

When I do tests that involve a third party C++ library,
then I compile that library several times, using the same
prefix as the compiler version that I use at that moment.
For example, I have installed libgmpxx for versions 2.96
and 3.2:

~/c++/libecc>locate libgmpxx
/usr/local/gcc-3.2/lib/libgmpxx.so.3.0.2
/usr/local/gcc-3.2/lib/libgmpxx.so.3
/usr/local/gcc-3.2/lib/libgmpxx.so
/usr/local/gcc-3.2/lib/libgmpxx.la
/usr/lib/libgmpxx.so.3
/usr/lib/libgmpxx.so.3.0.2
/usr/lib/libgmpxx.a
/usr/lib/libgmpxx.la
/usr/lib/libgmpxx.so

When using g++-2.96, this will of course find and link with
the one in /usr/lib, which was also compiled with 2.96.
When I use g++-3.2, then it DOES find and link with the
one in /usr/local/gcc-3.2/lib.  In other words: this works
perfectly and as it should.

Now comes libtool :( ...
In my current project I use in the configure.in file:

AC_CHECK_LIB(gmpxx, __gmpz_set)

When I have set CC=gcc-3.2 and CXX=g++-3.2, then it
uses that compiler version to find -lgmpxx ... and then
links in the end as:

gcc-3.2 -shared  libecc_la-debug.lo libecc_la-rng.lo libecc_la-sha.lo
    libecc_la-square.lo  -L/usr/lib/gcc-lib/i386-redhat-linux/2.96/../../..
    -L/usr/lib/gcc-lib/i386-redhat-linux/2.96/../../../../i386-redhat-linux/lib
    -L/usr/lib/gcc-lib/i386-redhat-linux/2.96 -L/usr/lib /usr/lib/libgmpxx.so
    -Wl,-soname -Wl,libecc.so.0 -o .libs/libecc.so.0.4.0

HORRIBLE!

Sorry, but only libtool can fuck up like that :/

Obviously it uses /usr/lib/libgmpxx.la for this '2.96' info.  That is 
ridiculous,
the compiler (g++-3.2) does NOT link with that - so why use it?

You should find out what the compiler actually USES and then search for a
'libgmpxx.la' in the same directory!

-- 
Carlo Wood <address@hidden>