Undefined reference to member function found in static library - c++

Question

I know what you're thinking - this has been answered a million times. I wish I could put something in the Title that would make it clear that I already know that the order of libraries is important.
I'm using g++ on Centos 6 64. I have a simple test program:
#include <ptlib.h>
int main()
{
PTimer indirectTimer1_;
indirectTimer1_.SetNotifier(0);
return 0;
}
and I compile and link it with this command:
g++ -I./ptlib/include/ mm.cpp ptlib/lib_linux_x86_64/libpt_s.a -lpthread -lrt
and I get this as an answer back:
/tmp/cc53itXb.o: In function `main':
mm.cpp:(.text+0x52): undefined reference to `PTimer::SetNotifier(PNotifierTemplate<int> const&)'
collect2: ld returned 1 exit status
But I know that PTimer::SetNotifier is in the .a file:
nm -AC ptlib/lib_linux_x86_64/libpt_s.a | grep SetNotifier
ptlib/lib_linux_x86_64/libpt_s.a:osutil.o:0000000000003dd8 T PTimer::SetNotifier(PNotifierTemplate<long> const&)
To make matters more confusing, when I compile the library on Centos 5, 32bit, and run the same test, it links just fine.
I've tried using '-Lptlib/lib_linux_x86_64 -lpt_s' and I've tried using the -Wl,--start-group / -Wl,--end-group args to no avail. If I add 'ptlib/src/ptlib/unix/osutil.cxx' to the g++ line, it compiles and links just fine. Unfortunately, this is but a sample of the unreferenced functions in our main program. Not all of the, just a few seemingly random methods like this one are undefined (which also links just fine on Centos 5, 32 bit).
As you can see, I've tried a lot of things but still haven't figured it out. I need something else to try! Or someone to point out something terribly easy that I am doing wrong.

Answer 1

undefined reference to `PTimer::SetNotifier(PNotifierTemplate<int> const&)'
PTimer::SetNotifier(PNotifierTemplate<long> const&)
Notice the difference in int vs. long?