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From: "moller at mollerware dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/94905] Bogus warning -Werror=maybe-uninitialized
Date: Thu, 02 Jul 2020 15:47:47 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D94905

Chris Moller <moller at mollerware dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |moller at mollerware dot c=
om

--- Comment #7 from Chris Moller <moller at mollerware dot com> ---
A little follow-up:

What's happening is that in gcc/tree-ssa-uninit.c, in
pass_late_warn_uninitialized::execute (function *fun),
warn_uninitialized_vars() is called with an argument of 1.  Then, in
warn_uninitialized_vars(), walk_aliased_vdefs (&ref, use, check_defs, &data,
NULL,&fentry_reached, limit); is called, returning with fentry_reached set =
to
false, which then leads to the warning being generated.

In gcc/tree-ssa-alias.c, in walk_aliased_vdefs_1(), *function_entry_reached=
 =3D
true; is never reached because gimple_nop_p (def_stmt) never returns true.

I've attached a bit of preprocessed sample code that reliably fails with=20

g++ -DHAVE_CONFIG_H -I. -I..    -Wall -I sql -Werror     -rdynamic -g -O2 -=
MT
apl-Shape.o -MD -MP -MF .deps/apl-Shape.Tpo -c Shape-preprocessed.cc=