https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103543

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |diagnostic
            Summary|Potential compiler warning  |Potential compiler warning
                   |for return of temporary?    |for return of temporary
                   |                            |with std::function<const
                   |                            |T&()> converting from
                   |                            |T(*)()

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
That is because the lambda itself returns a S and not a const reference.

You do get a warning with -Wsystem-headers inside invoke.

With:
[]() -> S const&  { return S{}; };

You do get the correct warning.

Also this has nothing to do with lambdas really but really std::function as
shown by:
struct S
{
  int s{};
};
using F = std::function<S const& ()>;
auto fn()
{
  return S{};
}
int main()
{
  F f = fn; // No warning
  __builtin_printf("%d.\n", f().s);
}
---- CUT ----
The above code is the same as the lambda case really.

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