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From: "antoshkka at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/96121] New: Uninitialized variable copying not diagnosed
Date: Wed, 08 Jul 2020 16:10:41 +0000
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X-Bugzilla-Product: gcc
X-Bugzilla-Component: c++
X-Bugzilla-Version: 11.0
X-Bugzilla-Keywords: diagnostic
X-Bugzilla-Severity: normal
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D96121

            Bug ID: 96121
           Summary: Uninitialized variable copying not diagnosed
           Product: gcc
           Version: 11.0
            Status: UNCONFIRMED
          Keywords: diagnostic
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: antoshkka at gmail dot com
  Target Milestone: ---

Consider the example:

struct A { A(); };
struct B { B(A); };

struct composed2 {
    B b_;
    A a_;
    composed2() : b_(a_)  {}
};


GCC does not diagnose the uninitialized variable `a_` usage with -Wall and
-Wextra. Some other compiler do diagnose:

warning: field 'a_' is uninitialized when used here [-Wuninitialized]
    composed2() : b_(a_)  {}
                     ^

Godbolt playground: https://godbolt.org/z/AbqzjR=