https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80824
Bug ID: 80824 Summary: Missing 'variable-is-used-uninitialized' warning Product: gcc Version: 7.1.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c Assignee: unassigned at gcc dot gnu.org Reporter: gccbugs at dima dot secretsauce.net Target Milestone: --- Created attachment 41387 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=41387&action=edit test case Hi. I'm using gcc 7.1.0 from Debian/experimental (Debian package gcc-7 version 7.1.0-5). I ran into a case where an uninitialized variable could be returned from a function without triggering a warning. With the attached minimized source tst.c the following does not yield a warning: gcc-7 -DCALL -DTEST2 -Wall -Wextra -o /dev/null -c tst.c Here I initialize some parts of the S structure (s.x), but not others (s.y). And I return the uninitialized piece: s.y. The extra f() call at the beginning of g() triggers the bug: taking that call out with gcc-7 -DTEST2 -Wall -Wextra -o /dev/null -c tst.c produces the warning as it should. Furthermore, initializing s.x in a slightly different way makes the bug go away as well: this produces the warning also: gcc-7 -DCALL -Wall -Wextra -o /dev/null -c tst.c Finally, it looks like gcc-6 had a similar issue where the extra call to f() makes the warning go away, but it was fixed in gcc-7: the following misses the warning: gcc-6 -DCALL -DTEST2 -Wall -Wextra -o /dev/null -c tst.c Maybe the fix to THIS bug would be similar. Thanks!