https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64003
--- Comment #10 from dmalcolm at gcc dot gnu.org --- Created attachment 34167 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=34167&action=edit Log from gdb session, with a conditional breakpoint to trap uninitialized reads This is a log of a gdb session debugging cc1 compiling the reproducer from comment #7, using the instrumentation patch from comment #8. I put a breakpoint on: fancy_element::operator int () const with condition that result == 0xabababab to handle reads of uninitialized elements from insn_lengths[]. I took a backtrace both times that the conditional breakpoint occurred.