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From: "egallager at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug tree-optimization/89976] [9/10/11/12 Regression] missing
 -Wuninitialized for struct member due to sra and TREE_NO_WARNING
Date: Sat, 26 Jun 2021 15:17:53 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D89976

--- Comment #6 from Eric Gallager <egallager at gcc dot gnu.org> ---
(In reply to Martin Sebor from comment #4)
> 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$x in
> case 1) has the TREE_NO_WARNING bit set.  This appears to be regression
> introduced in GCC 4.5 in r147980.
>=20
> gcc -O1 -S -Wall -std=3Dc++14 -fdump-tree-uninit=3D/dev/stdout pr89976.C=
=20
>=20
> ;; Function foo (_Z3foov, funcdef_no=3D3, decl_uid=3D2098, cgraph_uid=3D4,
> symbol_order=3D3)
>=20
> struct X foo ()
> {
>   int x$x;                             <<< TREE_NO_WARNING =3D=3D 1
>   struct X D.2133;
>=20
>   <bb 2> [local count: 1073741824]:
>   D.2133.x =3D x$x_2(D);                 <<< uninitialized read
>   D.2133.y =3D 0;
>   return D.2133;
>=20
> }
>=20
>=20
>=20
> ;; Function main (main, funcdef_no=3D4, decl_uid=3D2129, cgraph_uid=3D5,
> symbol_order=3D4) (executed once)
>=20
> int main ()
> {
>   int x$x;                             <<< TREE_NO_WARNING =3D=3D 1
>   struct X D.2156;
>   struct X x;
>=20
>   <bb 2> [local count: 1073741824]:
>   x =3D{v} {CLOBBER};
>   return x$x_5(D);                     <<< uninitialized read
>=20
> }

did your TREE_NO_WARNING overhaul affect this at all?=