https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111009
Bug ID: 111009 Summary: [12/13/14 regression] -fno-strict-overflow erroneously elides null pointer checks and causes SIGSEGV on perf from linux-6.4.10 Product: gcc Version: 14.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: middle-end Assignee: unassigned at gcc dot gnu.org Reporter: slyfox at gcc dot gnu.org Target Milestone: --- Initially observed the failure as a perf SIGSEGV when running against r14-3191-g614052dd4ea083. I hope I did not break it too much when minimizing. Self-contained example: // $ cat bug c.c struct dso { struct dso * next; int maj; }; __attribute__((noipa)) static void __dso_id__cmp_(void) {} __attribute__((noipa)) static int bug(struct dso * d, struct dso *dso) { struct dso **p = &d; struct dso *curr = 0; while (*p) { curr = *p; // prevent null deref below if (!dso) return 1; if (dso == curr) return 1; int *a = &dso->maj; // null deref if (!(a && *a)) __dso_id__cmp_(); p = &curr->next; } return 0; } __attribute__((noipa)) int main(void) { struct dso d = { 0, 0, }; bug(&d, 0); } Triggering the bug: $ gcc -fno-strict-overflow -O3 bug.c.c -o bug3 && ./bug3 Segmentation fault (core dumped) $ gcc -fno-strict-overflow -O2 bug.c.c -o bug2 && ./bug2 <ok> $ gcc -v Using built-in specs. COLLECT_GCC=/<<NIX>>/gcc-14.0.0/bin/gcc COLLECT_LTO_WRAPPER=/<<NIX>>/gcc-14.0.0/libexec/gcc/x86_64-unknown-linux-gnu/14.0.0/lto-wrapper Target: x86_64-unknown-linux-gnu Configured with: ../source/configure --prefix=/<<NIX>>/gcc-14.0.0 --with-gmp-include=/<<NIX>>/gmp-6.3.0-dev/include --with-gmp-lib=/<<NIX>>/gmp-6.3.0/lib --with-mpfr-include=/<<NIX>>/mpfr-4.2.0-12-dev/include --with-mpfr-lib=/<<NIX>>/mpfr-4.2.0-12/lib --with-mpc=/<<NIX>>/libmpc-1.3.1 --with-native-system-header-dir=/<<NIX>>/glibc-2.38-dev/include --with-build-sysroot=/ --program-prefix= --enable-lto --disable-libstdcxx-pch --without-included-gettext --with-system-zlib --enable-checking=release --enable-static --enable-languages=c,c++ --disable-multilib --enable-plugin --disable-libcc1 --with-isl=/<<NIX>>/isl-0.20 --disable-bootstrap --build=x86_64-unknown-linux-gnu --host=x86_64-unknown-linux-gnu --target=x86_64-unknown-linux-gnu Thread model: posix Supported LTO compression algorithms: zlib gcc version 14.0.0 99999999 (experimental) (GCC)