Direct C function call using GCC's inline assembly

I got the answer from GCC's mailing list:

asm("call %P0" : : "i"(callee));

Now I just need to find out what %P0 actually means because it seems to be an undocumented feature...

Edit: After looking at the GCC source code, it's not exactly clear what the code P in front of a constraint means. But, among other things, it prevents GCC from putting a $ in front of constant values. Which is exactly what I need in this case.

Maybe I am missing something here, but

extern "C" void callee(void) 
{

}

void caller(void)
{
  asm("call callee\n");
}

should work fine. You need extern "C" so that the name won't be decorated based on C++ naming mangling rules.