using AC_CHECK_LIB across different libc versions

[Rob Benton]

I could be trying this in the wrong way but the only way I've been able 
to get
AC_CHECK_LIB to work is by using the symbol of a function from one of my 
libraries.
Also I set the AC_LANG to C++.  But across different machines with different
compilers and versions of C++ libraries the symbols are different.  I've 
thought
about just writing my simple 'nm | grep' test but I wanted to get some 
advice first.
Am I going about this in the wrong way?

Thanks,
Rob