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From: "sbergman at redhat dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/98305] New: Incomprehensible -Wmismatched-new-delete warning
Date: Tue, 15 Dec 2020 22:10:25 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D98305

            Bug ID: 98305
           Summary: Incomprehensible -Wmismatched-new-delete warning
           Product: gcc
           Version: 11.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: sbergman at redhat dot com
  Target Milestone: ---

With recent GCC 11 trunk (at git commit
8dede2411195eb2fd672d8d0c758f94732bd6d77):

> $ cat test.cc
> #include <cstddef>
> template<typename> struct Reference {};
> template<typename> struct S2 {
>   static void * operator new(std::size_t);
>   static void operator delete(void *);
>   S2();
> };
> void f() { new S2<Reference<int>>; }

> $ g++ -Wmismatched-new-delete -c test.cc
> test.cc: In function =E2=80=98void f()=E2=80=99:
> test.cc:8:16: warning: =E2=80=98static void S2< <template-parameter-1-1> =
>::operator delete(void*) [with <template-parameter-1-1> =3D Reference<int>=
]=E2=80=99 called on pointer returned from a mismatched allocation function=
 [-Wmismatched-new-delete]
>     8 | void f() { new S2<Reference<int>>; }
>       |                ^~~~~~~~~~~~~~~~~~
> test.cc:8:16: note: returned from =E2=80=98static void* S2< <template-par=
ameter-1-1> >::operator new(std::size_t) [with <template-parameter-1-1> =3D=
 Reference<int>]=E2=80=99

(And oddly enough, the warning disappears when Reference is renamed to e.g.
S1.)=