Weak symbols vs. ptr-to-function: invalid optimisation or undefined behaviour?

[Paolo Bonzini]

>   if (!register_frame_fn)
>     register_frame_fn = __register_frame_info;

Yes, here __register_frame_info is assumed to be non-zero *for non-weak 
functions*, see tree_single_nonzero_warnv_p.  I don't know why your 
__register_frame_info is not seen as weak.

Paolo