https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106171
--- Comment #7 from Zhendong Su <zhendong.su at inf dot ethz.ch> --- (In reply to Jakub Jelinek from comment #5) > And -O1 -Wall warns: > pr106171.c: In function ‘c’: > pr106171.c:10:15: warning: ‘e[0]’ is used uninitialized [-Wuninitialized] > 10 | return e[0]; > | ~^~~ > pr106171.c:6:9: note: ‘e’ declared here > 6 | int e[2]; > | ^ Ah, this is quite clever of GCC :) Clang fails to detect and warn about it. CompCert lifts "int e[2]" to the same scope as "int d", thus also misses the UB.
