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From: "ed at catmur dot uk" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/111090] New: Bogus -Wuninitialized for trivial copy of
 nested struct with partially initialized array
Date: Mon, 21 Aug 2023 16:18:07 +0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: new
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: c++
X-Bugzilla-Version: 14.0
X-Bugzilla-Keywords: 
X-Bugzilla-Severity: normal
X-Bugzilla-Who: ed at catmur dot uk
X-Bugzilla-Status: UNCONFIRMED
X-Bugzilla-Resolution: 
X-Bugzilla-Priority: P3
X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D111090

            Bug ID: 111090
           Summary: Bogus -Wuninitialized for trivial copy of nested
                    struct with partially initialized array
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: ed at catmur dot uk
  Target Milestone: ---

struct A {
    A() { buf[0] =3D 0; }
    int buf[2];
};
struct B { A a; };
struct C {
    C(B const& b) : b(b) {}
    B b;
};
struct D {
    D(C c) : c(c) {}
    C c;
};
D f() { return D(C(B())); }

In constructor 'C::C(const B&)',
    inlined from 'D f()' at <source>:14:16:
<source>:7:21: warning: '<unnamed>.B::a.A::a[1]' is used uninitialized
[-Wuninitialized]
    7 |     C(B const& b) : b(b) {}
      |                     ^~~~
<source>: In function 'D f()':
<source>:14:22: note: '<anonymous>' declared here
   14 | D f() { return D(C(B())); }
      |                      ^

This appears to have started in 7.1.=