MacOS X 10.7.5 Lion. MacPro 4,1Intel dual CPU quad cores.
I've been away for a while so haven't worked on this. Back now and picking up the thread.

The bug is 13342 (see also 10015 and 10681) triggered by running
make check

> bad return from expression `(f-sum -1 2000 -30000 40000000000)': expected 39999971999; got 39999972255
> FAIL: test-ffi


There are 2 compilers available from Apple for C/C++ 
i686-apple-darwin11-llvm-gcc-4.2 (GCC) 4.2.1 (Based on Apple Inc. build 5658) (LLVM build 2336.1.00)
Apple clang version 3.0 (tags/Apple/clang-211.12) (based on LLVM 3.0svn)

I've built a standalone test with both of these compilers and they seem not to be the problem
Using the configure/make/make install is routine. But I am not familiar with the details of the make system.

I built guile-2.0.7 using the default configure/make and have 2 questions:
   (a) How can I find out which compiler/linker combo is used?
   (b) How can I change configure.ac to use the other one? (If that's the right place to make the change)

Thanks…

Peter