[Bug libstdc++/90943] Visiting inherited variants no longer works in 9.1

2022-04-12 Thread redi at gcc dot gnu.org via Gcc-bugs 
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90943

Jonathan Wakely  changed:

   What|Removed |Added

 Status|NEW |RESOLVED
 Resolution|--- |FIXED

--- Comment #12 from Jonathan Wakely  ---
Fixed for 11.3

[Bug libstdc++/90943] Visiting inherited variants no longer works in 9.1

2022-04-12 Thread cvs-commit at gcc dot gnu.org via Gcc-bugs 
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90943

--- Comment #11 from CVS Commits  ---
The releases/gcc-11 branch has been updated by Jonathan Wakely
:

https://gcc.gnu.org/g:90b94ca5a2ddd7834afff9ad5e1afff5554e0752

commit r11-9831-g90b94ca5a2ddd7834afff9ad5e1afff5554e0752
Author: Jonathan Wakely 
Date:   Mon Apr 19 14:49:12 2021 +0100

libstdc++: Allow visiting inherited variants [PR 90943]

Implement the changes from P2162R2 (as a DR for C++17).

Signed-off-by: Jonathan Wakely 

libstdc++-v3/ChangeLog:

PR libstdc++/90943
* include/std/variant (__cpp_lib_variant): Update value.
(__detail::__variant::__as): New helpers implementing the
as-variant exposition-only function templates.
(visit, visit): Use __as to upcast the variant parameters.
* include/std/version (__cpp_lib_variant): Update value.
* testsuite/20_util/variant/visit_inherited.cc: New test.

(cherry picked from commit c46ecb0112e91c80ee111439e79a58a953e4479d)

[Bug libstdc++/90943] Visiting inherited variants no longer works in 9.1

2021-10-01 Thread redi at gcc dot gnu.org via Gcc-bugs 
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90943

Jonathan Wakely  changed:

   What|Removed |Added

   Target Milestone|--- |11.3

--- Comment #10 from Jonathan Wakely  ---
Done for GCC 12, but I intend to backport it.

[Bug libstdc++/90943] Visiting inherited variants no longer works in 9.1

2021-10-01 Thread cvs-commit at gcc dot gnu.org via Gcc-bugs 
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90943

--- Comment #9 from CVS Commits  ---
The master branch has been updated by Jonathan Wakely :

https://gcc.gnu.org/g:c46ecb0112e91c80ee111439e79a58a953e4479d

commit r12-4067-gc46ecb0112e91c80ee111439e79a58a953e4479d
Author: Jonathan Wakely 
Date:   Mon Apr 19 14:49:12 2021 +0100

libstdc++: Allow visiting inherited variants [PR 90943]

Implement the changes from P2162R2 (as a DR for C++17).

Signed-off-by: Jonathan Wakely 

libstdc++-v3/ChangeLog:

PR libstdc++/90943
* include/std/variant (__cpp_lib_variant): Update value.
(__detail::__variant::__as): New helpers implementing the
as-variant exposition-only function templates.
(visit, visit): Use __as to upcast the variant parameters.
* include/std/version (__cpp_lib_variant): Update value.
* testsuite/20_util/variant/visit_inherited.cc: New test.

[Bug libstdc++/90943] Visiting inherited variants no longer works in 9.1

2021-05-12 Thread redi at gcc dot gnu.org via Gcc-bugs 
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90943

--- Comment #8 from Jonathan Wakely  ---
Corrected URL for downstream fix:
https://gitlab.com/jonathan-wakely/gcc/-/commit/486d89e403a18ef78f05f2efb1bc86bbd396899c

[Bug libstdc++/90943] Visiting inherited variants no longer works in 9.1

2021-04-19 Thread redi at gcc dot gnu.org via Gcc-bugs 
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90943

--- Comment #7 from Jonathan Wakely  ---
Implemented downstream:
https://gitlab.com/jonathan-wakely/gcc/-/commit/484308ad163862632ae7e710c5d909be385450aa

[Bug libstdc++/90943] Visiting inherited variants no longer works in 9.1

2021-02-23 Thread redi at gcc dot gnu.org via Gcc-bugs 
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90943

Jonathan Wakely  changed:

   What|Removed |Added

 Status|SUSPENDED   |NEW

--- Comment #6 from Jonathan Wakely  ---
http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2021/p2162r2.html says we
should support inherited variants.

[Bug libstdc++/90943] Visiting inherited variants no longer works in 9.1

2020-05-03 Thread redi at gcc dot gnu.org 
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90943

Jonathan Wakely  changed:

   What|Removed |Added

   Target Milestone|9.4 |---

[Bug libstdc++/90943] Visiting inherited variants no longer works in 9.1

2020-03-12 Thread jakub at gcc dot gnu.org 
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90943

Jakub Jelinek  changed:

   What|Removed |Added

   Target Milestone|9.3 |9.4

--- Comment #5 from Jakub Jelinek  ---
GCC 9.3.0 has been released, adjusting target milestone.

[Bug libstdc++/90943] Visiting inherited variants no longer works in 9.1

2019-08-12 Thread jakub at gcc dot gnu.org 
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90943

Jakub Jelinek  changed:

   What|Removed |Added

   Target Milestone|9.2 |9.3

--- Comment #4 from Jakub Jelinek  ---
GCC 9.2 has been released.

[Bug libstdc++/90943] Visiting inherited variants no longer works in 9.1

2019-06-20 Thread redi at gcc dot gnu.org 
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90943

Jonathan Wakely  changed:

   What|Removed |Added

 Status|ASSIGNED|SUSPENDED

--- Comment #3 from Jonathan Wakely  ---
https://wg21.link/LWG3052 would forbid us from supporting this.

[Bug libstdc++/90943] Visiting inherited variants no longer works in 9.1

2019-06-20 Thread redi at gcc dot gnu.org 
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90943

Jonathan Wakely  changed:

   What|Removed |Added

 Status|UNCONFIRMED |ASSIGNED
   Last reconfirmed||2019-06-20
   Assignee|unassigned at gcc dot gnu.org  |redi at gcc dot gnu.org
   Target Milestone|--- |9.2
 Ever confirmed|0   |1

[Bug libstdc++/90943] Visiting inherited variants no longer works in 9.1

2019-06-19 Thread barry.revzin at gmail dot com 
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90943

--- Comment #2 from Barry Revzin  ---
What if we did something like (using pretty names for a sec):

template 
struct _Extra_visit_slot_needed
{
  template 
  static bool_constant<__never_valueless<_Types...>()>
  __impl(const variant<_Types...>&);
  static false_type __impl(...);

  using _Variant_never_valueless = decltype(__impl(declval<_Variant>()));


  static constexpr bool value =
(is_same_v<_Maybe_variant_cookie, __variant_cookie>
 || is_same_v<_Maybe_variant_cookie, __variant_idx_cookie>)
 && !_Variant_never_valueless::value;
};

This should (modulo typos) work for real variant instantiations and also
anything that inherits from some variant instantiation?

[Bug libstdc++/90943] Visiting inherited variants no longer works in 9.1

2019-06-19 Thread redi at gcc dot gnu.org 
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90943

Jonathan Wakely  changed:

   What|Removed |Added

  Component|c++ |libstdc++

--- Comment #1 from Jonathan Wakely  ---
This is all it takes to compile your example:

--- a/libstdc++-v3/include/std/variant
+++ b/libstdc++-v3/include/std/variant
@@ -795,7 +795,7 @@ namespace __variant
   template 
 struct _Extra_visit_slot_needed
 {
-  template  struct _Variant_never_valueless;
+  template  struct _Variant_never_valueless : false_type { };

   template 
struct _Variant_never_valueless>

This just assumes that unrecognized types are not never-valueless variants,
which means some extra code gets generated to handle the valueless case even if
your variant base class will never be valueless.

I haven't considered if anything else would break by doing that.