osx and thread safety?

Can someone shed some light on the thread safety
switch. I am using PostgreSQL on mac os x. I have made
and installed from 7.2 through 8.0b. I now see this
feature of thread safety and I don't understand why I
would need it.

I have tried:

./configure --with-rendezvous --enable-thread-safety

I get these errors:

ld: common symbols not allowed with MH_DYLIB output
format with the -multi_module option
fe-secure.o definition of common _thread_in_send (size
4)
/usr/bin/libtool: internal link edit command failed
make[3]: *** [libpq.3.2.dylib] Error 1
make[2]: *** [all] Error 2
make[1]: *** [all] Error 2
make: *** [all] Error 2

this is os x 10.3.5 with gcc (GCC) 3.3

any ideas (If I don't know what it is, do I need it?)

Ted

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