https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78391
Martin Sebor <msebor at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Known to fail| |10.2.0, 11.0, 7.3.0, 8.3.0, | |9.2.0 CC| |msebor at gcc dot gnu.org Last reconfirmed|2016-11-17 00:00:00 |2021-3-31 --- Comment #4 from Martin Sebor <msebor at gcc dot gnu.org> --- Reconfirmed with GCC 11. GCC does issue -Wuninitialized without optimization on an equivalent test case with an explicit ctor. The difference between the two ctors is that B's has a clobber: $ cat pr78391.C && PRED_DUMP=euninit gcc -S -Wall pr78391.C struct A { int x = w; int w = 10; }; int f () { A a; return a.x; } struct B { int x, w; B (): x(w), w (10) { } }; int g () { B b; return b.x; } void A::A (struct A * const this) { int _1; <bb 2> : # VUSE <.MEM_2(D)> <<< no clobber _1 = this_3(D)->w; <<< -Wuninitialized # .MEM_4 = VDEF <.MEM_2(D)> this_3(D)->x = _1; # .MEM_5 = VDEF <.MEM_4> this_3(D)->w = 10; # VUSE <.MEM_5> return; } int f () { struct A a; int D.2439; int _3; <bb 2> : # .MEM_2 = VDEF <.MEM_1(D)> A::A (&a); # VUSE <.MEM_2> _3 = a.x; # .MEM_4 = VDEF <.MEM_2> a ={v} {CLOBBER}; <bb 3> : <L1>: # VUSE <.MEM_4> return _3; } void B::B (struct B * const this) { int _1; <bb 2> : # .MEM_4 = VDEF <.MEM_2(D)> *this_3(D) ={v} {CLOBBER}; <<< clobber here # VUSE <.MEM_4> _1 = this_3(D)->w; <<< -Wuninitialized # .MEM_5 = VDEF <.MEM_4> this_3(D)->x = _1; # .MEM_6 = VDEF <.MEM_5> this_3(D)->w = 10; # VUSE <.MEM_6> return; } pr78391.C: In constructor ‘B::B()’: pr78391.C:9:30: warning: ‘*this.B::w’ is used uninitialized [-Wuninitialized] 9 | struct B { int x, w; B (): x(w), w (10) { } }; | ^ int g () { struct B b; int D.2442; int _3; <bb 2> : # .MEM_2 = VDEF <.MEM_1(D)> B::B (&b); # VUSE <.MEM_2> _3 = b.x; # .MEM_4 = VDEF <.MEM_2> b ={v} {CLOBBER}; <bb 3> : <L1>: # VUSE <.MEM_4> return _3; }