relocation R_X86_64_32 / -fPIC issues with certain ports

[Conrad J. Sabatier]

I've encountered this problem before while building certain ports for
amd64, but I've decided it's time to ask for some details as to what it
means exactly.

Here's a sample from a failed build of devel/subversion:

/usr/bin/ld:
../libsvn_swig_perl/.libs/libsvn_swig_perl-1.a(swigutil_pl.o):
relocation R_X86_64_32 can not be used when making a shared object;
recompile with -fPIC

OK, I know that adding "-fPIC" to this or that Makefile resolves this
issue, but can anyone explain what this is actually all about?

Thanks!

-- 
Conrad J. Sabatier <conrads at cox.net> -- "In Unix veritas"