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From: "ed at catmur dot uk" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug libstdc++/110493] New: 'is not a constant expression' for
 function-local static std::initializer_list<std::string> with
 fsanitize=undefined
Date: Fri, 30 Jun 2023 04:29:43 +0000
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X-Bugzilla-Type: new
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X-Bugzilla-Product: gcc
X-Bugzilla-Component: libstdc++
X-Bugzilla-Version: 12.3.0
X-Bugzilla-Keywords: 
X-Bugzilla-Severity: normal
X-Bugzilla-Who: ed at catmur dot uk
X-Bugzilla-Status: UNCONFIRMED
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X-Bugzilla-Priority: P3
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D110493

            Bug ID: 110493
           Summary: 'is not a constant expression' for function-local
                    static std::initializer_list<std::string> with
                    fsanitize=3Dundefined
           Product: gcc
           Version: 12.3.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: ed at catmur dot uk
  Target Milestone: ---

Since 12.3.0, under -fsanitize=3Dundefined -std=3Dc++20:

#include <initializer_list>
#include <string>
void f() {
    static auto a =3D {std::string()};
}

error: '(((const std::__cxx11::basic_string<char>*)(& <temporary>)) !=3D 0)=
' is
not a constant expression

Clearly this is an instance of bug 71962, but this is in fairly unexception=
al
code and could make ubsan unusable; it's not obvious that this code should =
have
anything to do with constant evaluation.

Since it only appears in a point release I would hope it might be possible =
to
fix in library for this specific case, within <initializer_list>?=