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From: "igkper at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug sanitizer/109991] New: stack-use-after-scope
Date: Fri, 26 May 2023 14:43:38 +0000
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X-Bugzilla-Component: sanitizer
X-Bugzilla-Version: 14.0
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D109991

            Bug ID: 109991
           Summary: stack-use-after-scope
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: sanitizer
          Assignee: unassigned at gcc dot gnu.org
          Reporter: igkper at gmail dot com
                CC: dodji at gcc dot gnu.org, dvyukov at gcc dot gnu.org,
                    jakub at gcc dot gnu.org, kcc at gcc dot gnu.org, marxi=
n at gcc dot gnu.org
  Target Milestone: ---

Hi,

I believe the below code should result in sanitizer complaining about
stack-use-after-scope, but it does not. I've noted that clang catches this =
but
not gcc. I've annotated where I've noted it seems to depend on whether or n=
ot
constexpr is used. See  https://godbolt.org/z/Y3YKcfGda.

using T =3D int;

struct Wrap
{
    T const& v;

    // Shouldn't extend lifetime of temporary
    constexpr Wrap(T const& in) : v{in} {}
};

struct BadWrapUse final
{
    T i{};

    constexpr BadWrapUse()  // issue not caught with constexpr
    // BadWrapUse()  // issue caught without constexpr
    {
        Wrap w{T{}};  // temporary T's lifetime ends after this expression
        i =3D w.v;      // This should lead to stack-use-after-scope.
    }
};

int main()
{
    BadWrapUse c;
}=