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From: "msebor at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug middle-end/100684] New: spurious -Wnonnull with -O1 on a C++
 lambda
Date: Wed, 19 May 2021 15:59:19 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D100684

            Bug ID: 100684
           Summary: spurious -Wnonnull with -O1 on a C++ lambda
           Product: gcc
           Version: 11.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: middle-end
          Assignee: unassigned at gcc dot gnu.org
          Reporter: msebor at gcc dot gnu.org
  Target Milestone: ---

>>From James Legg in comment pr98109 comment 2:

> The false positives can often be seen when converting a lambda to a funct=
ion
> pointer at lower optimisation levels too. For example, in g++ 11.1.1,
> compiling:
> int main()
> {
> 	return static_cast<int (*)(int)>([](int x){ return x; })(0);
> }
>=20
> with -Og -Wall -fsanitize=3Dundefined results in:
> /tmp/a.cc: In static member function =E2=80=98static constexpr int
> main()::<lambda(int)>::_FUN(int)=E2=80=99:
> /tmp/a.cc:3:63: warning: =E2=80=98this=E2=80=99 pointer is null [-Wnonnul=
l]
>     3 |         return static_cast<int (*)(int)>([](int x){ return x; })(=
0);
>       |                                                               ^
> /tmp/a.cc:3:42: note: in a call to non-static member function
> =E2=80=98main()::<lambda(int)>=E2=80=99
>     3 |         return static_cast<int (*)(int)>([](int x){ return x; })(=
0);
>       |                                          ^=