https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112550
--- Comment #2 from David Binderman <dcb314 at hotmail dot com> --- (In reply to Sam James from comment #1) > Not sure if I'm misunderstanding you, but it's not trivial to go from -O0 > and -O1 and it's "normal" to have a difference in output in either the case > of: a) UB, or b) a compiler bug (miscompilation). The source code I provided is produced by csmith and then preprocessed. I tried the upstream unpreprocessed source code on clang -O0 and gcc -O0 and they agreed on the output, so it looked to me like csmith was working ok. Only when I changed over from gcc -O0 to gcc -O1 did I see a difference.
