Sure, but I think that's independent of what eMSF was describing. From libgcc/gthr.h:
/* If this file is compiled with threads support, it must
#define __GTHREADS 1
to indicate that threads support is present. Also it has define
function
int __gthread_active_p ()
that returns 1 if thread system is active, 0 if not.
I think the mechanism eMSF was describing (and the mechanism in the blogpost I linked) corresponds to __gthread_active_p().
I think the distinction between the two should be visible in some cases - for example, what happens for shared libraries that use std::shared_ptr and don't link libpthread, but are later used with a binary that does link libpthread?
