Where does VMError::print_native_stack and os::get_sender_for_C_frame load/use the frame pointer?

[Julian Waters]

Hi Dean,

I eventually did find frame::link(), but ultimately it didn't seem to help as VMError::print_native_stack still doesn't work properly on Windows. It seems as though frame::link() calls addr_at on x86, which in turn calls frame::fp(), which returns _fp. I think whatever sets _fp for VMError::print_native_stack is the missing link here, but unfortunately I don't know where it's set

The code that I tried on Windows x64 is attached below

best regards,
Julian

// VC++ does not save frame pointer on stack in optimized build. It
// can be turned off by -Oy-. If we really want to walk C frames,
// we can use the StackWalk() API.
frame os::get_sender_for_C_frame(frame* fr) {
#ifdef __GNUC__
  return frame(fr->sender_sp(), fr->link(), fr->sender_pc());
#elif defined(_MSC_VER)
  ShouldNotReachHere();
  return frame();
#endif
}

frame os::current_frame() {
#ifdef __GNUC__
  frame f(reinterpret_cast<intptr_t*>(os::current_stack_pointer()),
          reinterpret_cast<intptr_t*>(__builtin_frame_address(1)),
          CAST_FROM_FN_PTR(address, &os::current_frame));
  if (os::is_first_C_frame(&f)) {
    // stack is not walkable
    return frame();
  } else {
    return os::get_sender_for_C_frame(&f);
  }
#elif defined(_MSC_VER)
  return frame();  // cannot walk Windows frames this way.  See os::get_native_stack
                   // and os::platform_print_native_stack
#endif
}