https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108996
--- Comment #10 from Jakub Jelinek <jakub at gcc dot gnu.org> --- (In reply to Ulrich Weigand from comment #8) > (In reply to Jakub Jelinek from comment #5) > > Though, relying on DW_OP_entry_value is not reliable, if e.g. tail calls are > > (or could be) involved, then GDB needs to punt. > > The only way a tail call could happen is if the return value is > passed through directly to the (caller's) caller, so the return > buffer address should still be correct, right? If there is just a single possible tail call, I think GDB still handles it, so that would be ok. But if you have multiple possible tail calls, I think GDB for DW_OP_entry_value evaluation punts (at least should, because it doesn't know which sequence of calls has been taken). > I don't think it is possible to track the value in the callee - the value > may not be available *anywhere* because it is no longer needed. (Also, I > don't think the implicit return buffer address is guaranteed to be spilled > to the stack even at -O0.) Well, at -O0 we can certainly guarantee it is available somewhere, even if we currently don't do it already (it would surprise me if it is not spilled).
