[Bug c++/110824] New: Gcc crashing on a lambda capture

[Bug c++/110824] New: Gcc crashing on a lambda capture

[denis.yaroshevskij at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110824

            Bug ID: 110824
           Summary: Gcc crashing on a lambda capture
           Product: gcc
           Version: 11.3.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: denis.yaroshevskij at gmail dot com
  Target Milestone: ---

Created attachment 55646
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=55646&action=edit
ninja.log and .ii file

Attaching ninja log and a .ii file
Let me know if you need anyting else.

[Bug c++/110824] Gcc crashing on a lambda capture

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110824

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Reducing to see if it is reproducible on the trunk ...

[Bug c++/110824] Gcc crashing on a lambda capture

[denis.yaroshevskij at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110824

--- Comment #2 from Denis Yaroshevskiy <denis.yaroshevskij at gmail dot com> ---
FYI, this is my workaround:

```

template<typename Selector> struct just_shuffle_test_selector
{
  Selector sel;

  template<typename... Args>
  auto operator()(Args... args) const
  requires(std::invocable<Selector, Args...>)
  {
    auto r = sel(args...);
    if constexpr( !eve::detail::matched_shuffle<decltype(r)> )
    {
      return kumi::tuple {r, eve::index<-1>};
    }
    else return kumi::tuple {r, eve::index<0>};
  }
};

template<typename Selector>
just_shuffle_test_selector(Selector) -> just_shuffle_test_selector<Selector>;

template<typename WrappedShuffleV2> struct just_shuffle_test_
{
  WrappedShuffleV2 sh2;


  template<typename... Args>
  auto operator()(Args... args) const
  requires(std::invocable<WrappedShuffleV2, Args...>)
  {
    return get<0>(sh2(args...));
  }
};

template<typename WrappedShuffleV2>
just_shuffle_test_(WrappedShuffleV2) -> just_shuffle_test_<WrappedShuffleV2>;


template<typename Selector>
constexpr auto
just_shuffle_test(Selector selector)
{
  return
just_shuffle_test_{eve::detail::make_shuffle_v2(just_shuffle_test_selector{selector})};
}
```

[Bug c++/110824] Gcc crashing on a lambda capture

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110824

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|---                         |DUPLICATE

--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Reduced testcase:
```
namespace t {
struct tt {};
template <int a> int get(tt b) { return 1; }
}
void g() {
  auto wrapped = [](int) { return t::tt{}; };
  [&wrapped](auto t) -> decltype(get<0>(wrapped(t))) { return 1; }(1);
}

```

Which makes this a dup of bug 110524.

*** This bug has been marked as a duplicate of bug 110524 ***

[Bug c++/110824] Gcc crashing on a lambda capture

[denis.yaroshevskij at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110824

--- Comment #4 from Denis Yaroshevskiy <denis.yaroshevskij at gmail dot com> ---
Appreciate it.

I'm still going to support gcc11 for the forseable future. Is there some easy
way you see I can confirm that this is this issue?
So that I don't create more duplicates?

[Bug c++/110824] Gcc crashing on a lambda capture

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110824

--- Comment #5 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to Denis Yaroshevskiy from comment #4)
> Appreciate it.
> 
> I'm still going to support gcc11 for the forseable future. Is there some
> easy way you see I can confirm that this is this issue?
> So that I don't create more duplicates?

In this case, the pattern is simple is there a trailing return type and does it
use decltype with a template function and is that template function defined
(and in that scope or outer scope) then this will be a dup of that issue. (it
is only valid C++20 rather than being valid C++17 too).

Hope that helps. 

Also note C++20 support in GCC is still being fixed in many areas too so using
GCC 11 which came out less than 4 months after C++20 was ratification and
published is definitely going to be an issue.