You do mean gcc 4.3 right (either a snapshot, or from svn)?
Since you're running on x86_64, do you know that the libraries are the correct bitness (running 'file' on the mpfr and gmp libraries will tell). By default gcc on x86_64 will build 64-bit, but libraries in /usr/local/lib should only be 32-bit (versus /usr/local/ lib64). The linker will ignore any 32-bit libraries when linking a 64- bit executable. How did you install gmp/mpfr (note the package from fedora is broken -- very old)?
It took me quite a while to get 4.1 with fortran installed on RHEL until I got this all sorted out (I was new to multilibs). I just upgraded to fc6 and was able to install gcc from svn once I used -- with-gmp-lib=/usr/local/lib64 (etc for include and mpfr) and setting LD_LIBRARY_PATH=/usr/local/lib64 appropriately. Alternatively one could (carefully!) setup /etc/ld.so.conf and run ldconfig (I did this on RHEL).
I might be able to help tomorrow AM (US mountain time) if you email me directly.
FWIW, I understand the reason to keep mpfr out of the gcc tree, but not doing so makes gcc more difficult to bootstrap for a novice such as myself. Fedora's outdated gmp/mpfr package doesn't help either ...
- Matt
