https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66896
--- Comment #11 from Vittorio Zecca <zeccav at gmail dot com> --- I have a version of gcc 5.2.0 compiled with the -fsanitize=undefined option. This sanitized version gave me a runtime error due to dereferencing the pointer dst_ctx which was NULL. After the change I suggested the message disappeared. You may double check my finding, as I did myself, by putting assert(dst_ctx) before its dereferencing in ipa-prop.c as in assert(dst_ctx),dst_ctx->combine_with (ctx); It happens twice in isa-prop.c Then try it with the two C codes I sent, with option -O2
