https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89976
Martin Sebor <msebor at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Component|c++ |tree-optimization Summary|missing uninitialized |[9/10/11 Regression] |warning for uninitialized |missing -Wuninitialized for |struct member (VOPs) |struct member due to sra | |and TREE_NO_WARNING Last reconfirmed|2019-11-02 00:00:00 |2021-4-16 CC| |msebor at gcc dot gnu.org Known to fail| |10.2.0, 11.0, 4.5.3, 4.6.4, | |4.9.4, 5.5.0, 6.4.0, 7.2.0, | |8.3.0, 9.1.0 --- Comment #4 from Martin Sebor <msebor at gcc dot gnu.org> --- In all cases and with -O1 and above, the uninitialized read is clearly visible in the IL but it's suppressed because the variable (such as x$x in case 1) has the TREE_NO_WARNING bit set. This appears to be regression introduced in GCC 4.5 in r147980. gcc -O1 -S -Wall -std=c++14 -fdump-tree-uninit=/dev/stdout pr89976.C ;; Function foo (_Z3foov, funcdef_no=3, decl_uid=2098, cgraph_uid=4, symbol_order=3) struct X foo () { int x$x; <<< TREE_NO_WARNING == 1 struct X D.2133; <bb 2> [local count: 1073741824]: D.2133.x = x$x_2(D); <<< uninitialized read D.2133.y = 0; return D.2133; } ;; Function main (main, funcdef_no=4, decl_uid=2129, cgraph_uid=5, symbol_order=4) (executed once) int main () { int x$x; <<< TREE_NO_WARNING == 1 struct X D.2156; struct X x; <bb 2> [local count: 1073741824]: x ={v} {CLOBBER}; return x$x_5(D); <<< uninitialized read }