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* [Bug c++/100384] New: Compiling in c++17 mode breaks compilation of functions named visit()
@ 2021-05-02 15:38 aacid at kde dot org
2021-05-02 15:38 ` [Bug c++/100384] " aacid at kde dot org
` (10 more replies)
0 siblings, 11 replies; 12+ messages in thread
From: aacid at kde dot org @ 2021-05-02 15:38 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100384
Bug ID: 100384
Summary: Compiling in c++17 mode breaks compilation of
functions named visit()
Product: gcc
Version: 10.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: aacid at kde dot org
Target Milestone: ---
Created attachment 50733
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=50733&action=edit
main.cpp
The attached code fails to compile with
g++ --std=c++17 main.cpp
I've tried with gcc 11.1 too and it fails too.
To me it seems a bug in the implementation in which std::visit is leaking into
the non std:: namespace, but maybe it's a bug in C++ specification?
^ permalink raw reply [flat|nested] 12+ messages in thread
* [Bug c++/100384] Compiling in c++17 mode breaks compilation of functions named visit()
2021-05-02 15:38 [Bug c++/100384] New: Compiling in c++17 mode breaks compilation of functions named visit() aacid at kde dot org
@ 2021-05-02 15:38 ` aacid at kde dot org
2021-05-03 12:59 ` [Bug libstdc++/100384] " aacid at kde dot org
` (9 subsequent siblings)
10 siblings, 0 replies; 12+ messages in thread
From: aacid at kde dot org @ 2021-05-02 15:38 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100384
--- Comment #1 from Albert Astals Cid <aacid at kde dot org> ---
Created attachment 50734
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=50734&action=edit
error log
^ permalink raw reply [flat|nested] 12+ messages in thread
* [Bug libstdc++/100384] Compiling in c++17 mode breaks compilation of functions named visit()
2021-05-02 15:38 [Bug c++/100384] New: Compiling in c++17 mode breaks compilation of functions named visit() aacid at kde dot org
2021-05-02 15:38 ` [Bug c++/100384] " aacid at kde dot org
@ 2021-05-03 12:59 ` aacid at kde dot org
2021-05-03 14:08 ` redi at gcc dot gnu.org
` (8 subsequent siblings)
10 siblings, 0 replies; 12+ messages in thread
From: aacid at kde dot org @ 2021-05-03 12:59 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100384
--- Comment #2 from Albert Astals Cid <aacid at kde dot org> ---
People that know more C++ than me, told me
std::visit appears unconstrained to Variants...&& being actual std::variants
(in case you inherited one, I guess), so std::visit, as an unconstrained
perfect forwarder will win every overload set ranking. And std::visit is
brought in by ADL via std::vector
it's a misfeature, this has been adopted in C++23
http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2021/p2162r2.html
So I guess the proper resolution for this issue would be "not a bug", but will
leave you to decide on it :)
^ permalink raw reply [flat|nested] 12+ messages in thread
* [Bug libstdc++/100384] Compiling in c++17 mode breaks compilation of functions named visit()
2021-05-02 15:38 [Bug c++/100384] New: Compiling in c++17 mode breaks compilation of functions named visit() aacid at kde dot org
2021-05-02 15:38 ` [Bug c++/100384] " aacid at kde dot org
2021-05-03 12:59 ` [Bug libstdc++/100384] " aacid at kde dot org
@ 2021-05-03 14:08 ` redi at gcc dot gnu.org
2021-05-03 14:44 ` ppalka at gcc dot gnu.org
` (7 subsequent siblings)
10 siblings, 0 replies; 12+ messages in thread
From: redi at gcc dot gnu.org @ 2021-05-03 14:08 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100384
Jonathan Wakely <redi at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |RESOLVED
Resolution|--- |INVALID
--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Not a bug.
PR 90943 already exists for the P2162R3 support.
^ permalink raw reply [flat|nested] 12+ messages in thread
* [Bug libstdc++/100384] Compiling in c++17 mode breaks compilation of functions named visit()
2021-05-02 15:38 [Bug c++/100384] New: Compiling in c++17 mode breaks compilation of functions named visit() aacid at kde dot org
` (2 preceding siblings ...)
2021-05-03 14:08 ` redi at gcc dot gnu.org
@ 2021-05-03 14:44 ` ppalka at gcc dot gnu.org
2021-05-03 19:51 ` redi at gcc dot gnu.org
` (6 subsequent siblings)
10 siblings, 0 replies; 12+ messages in thread
From: ppalka at gcc dot gnu.org @ 2021-05-03 14:44 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100384
Patrick Palka <ppalka at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |ppalka at gcc dot gnu.org
--- Comment #4 from Patrick Palka <ppalka at gcc dot gnu.org> ---
Hmm, isn't problem here ultimately that std::visit is specified to have a
concrete SFINAE-friendly return type, but our implementation uses a deduced
return type?
^ permalink raw reply [flat|nested] 12+ messages in thread
* [Bug libstdc++/100384] Compiling in c++17 mode breaks compilation of functions named visit()
2021-05-02 15:38 [Bug c++/100384] New: Compiling in c++17 mode breaks compilation of functions named visit() aacid at kde dot org
` (3 preceding siblings ...)
2021-05-03 14:44 ` ppalka at gcc dot gnu.org
@ 2021-05-03 19:51 ` redi at gcc dot gnu.org
2021-05-03 20:02 ` redi at gcc dot gnu.org
` (5 subsequent siblings)
10 siblings, 0 replies; 12+ messages in thread
From: redi at gcc dot gnu.org @ 2021-05-03 19:51 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100384
--- Comment #5 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Possibly, but it needs to be constrained for p2162 anyway, which I'm doing via
the return type.
^ permalink raw reply [flat|nested] 12+ messages in thread
* [Bug libstdc++/100384] Compiling in c++17 mode breaks compilation of functions named visit()
2021-05-02 15:38 [Bug c++/100384] New: Compiling in c++17 mode breaks compilation of functions named visit() aacid at kde dot org
` (4 preceding siblings ...)
2021-05-03 19:51 ` redi at gcc dot gnu.org
@ 2021-05-03 20:02 ` redi at gcc dot gnu.org
2021-05-04 11:19 ` cvs-commit at gcc dot gnu.org
` (4 subsequent siblings)
10 siblings, 0 replies; 12+ messages in thread
From: redi at gcc dot gnu.org @ 2021-05-03 20:02 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100384
Jonathan Wakely <redi at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Resolution|INVALID |---
Ever confirmed|0 |1
Last reconfirmed| |2021-05-03
Status|RESOLVED |NEW
--- Comment #6 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Yes, we can fix this easily without the rest of P2162 (and can backport it):
--- a/libstdc++-v3/include/std/variant
+++ b/libstdc++-v3/include/std/variant
@@ -1248,7 +1248,8 @@ namespace __variant
#endif
template<typename _Visitor, typename... _Variants>
- constexpr decltype(auto) visit(_Visitor&&, _Variants&&...);
+ constexpr invoke_result_t<_Visitor, variant_alternative_t<0,
_Variants>...>
+ visit(_Visitor&&, _Variants&&...);
template<typename... _Types>
inline enable_if_t<(is_move_constructible_v<_Types> && ...)
@@ -1736,7 +1737,7 @@ namespace __variant
template<typename _Visitor, typename... _Variants>
- constexpr decltype(auto)
+ constexpr invoke_result_t<_Visitor, variant_alternative_t<0,
_Variants>...>
visit(_Visitor&& __visitor, _Variants&&... __variants)
{
if ((__variants.valueless_by_exception() || ...))
^ permalink raw reply [flat|nested] 12+ messages in thread
* [Bug libstdc++/100384] Compiling in c++17 mode breaks compilation of functions named visit()
2021-05-02 15:38 [Bug c++/100384] New: Compiling in c++17 mode breaks compilation of functions named visit() aacid at kde dot org
` (5 preceding siblings ...)
2021-05-03 20:02 ` redi at gcc dot gnu.org
@ 2021-05-04 11:19 ` cvs-commit at gcc dot gnu.org
2021-05-06 13:06 ` cvs-commit at gcc dot gnu.org
` (3 subsequent siblings)
10 siblings, 0 replies; 12+ messages in thread
From: cvs-commit at gcc dot gnu.org @ 2021-05-04 11:19 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100384
--- Comment #7 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Jonathan Wakely <redi@gcc.gnu.org>:
https://gcc.gnu.org/g:af5b2b911dd80ae9cc87404b7e7ab807cf6655d4
commit r12-436-gaf5b2b911dd80ae9cc87404b7e7ab807cf6655d4
Author: Jonathan Wakely <jwakely@redhat.com>
Date: Tue May 4 12:16:46 2021 +0100
libstdc++: Do not use deduced return type for std::visit [PR 100384]
This avoids errors outside the immediate context when std::visit is an
overload candidate because of ADL, but not actually viable.
The solution is to give std::visit a non-deduced return type. New
helpers are introduced for that, and existing ones refactored slightly.
libstdc++-v3/ChangeLog:
PR libstdc++/100384
* include/std/variant (__get_t): New alias template yielding the
return type of std::get<N> on a variant.
(__visit_result_t): New alias template yielding the result of
std::visit.
(__same_types): Move into namespace __detail::__variant.
(__check_visitor_results): Likewise. Use __invoke_result_t and
__get_t.
(__check_visitor_result): Remove.
(visit): Use __visit_result_t for return type.
* testsuite/20_util/variant/100384.cc: New test.
^ permalink raw reply [flat|nested] 12+ messages in thread
* [Bug libstdc++/100384] Compiling in c++17 mode breaks compilation of functions named visit()
2021-05-02 15:38 [Bug c++/100384] New: Compiling in c++17 mode breaks compilation of functions named visit() aacid at kde dot org
` (6 preceding siblings ...)
2021-05-04 11:19 ` cvs-commit at gcc dot gnu.org
@ 2021-05-06 13:06 ` cvs-commit at gcc dot gnu.org
2021-06-18 12:56 ` cvs-commit at gcc dot gnu.org
` (2 subsequent siblings)
10 siblings, 0 replies; 12+ messages in thread
From: cvs-commit at gcc dot gnu.org @ 2021-05-06 13:06 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100384
--- Comment #8 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-11 branch has been updated by Jonathan Wakely
<redi@gcc.gnu.org>:
https://gcc.gnu.org/g:e99763ee6da8e378073b847243d9ac2538903534
commit r11-8363-ge99763ee6da8e378073b847243d9ac2538903534
Author: Jonathan Wakely <jwakely@redhat.com>
Date: Tue May 4 12:16:46 2021 +0100
libstdc++: Do not use deduced return type for std::visit [PR 100384]
This avoids errors outside the immediate context when std::visit is an
overload candidate because of ADL, but not actually viable.
The solution is to give std::visit a non-deduced return type. New
helpers are introduced for that, and existing ones refactored slightly.
libstdc++-v3/ChangeLog:
PR libstdc++/100384
* include/std/variant (__get_t): New alias template yielding the
return type of std::get<N> on a variant.
(__visit_result_t): New alias template yielding the result of
std::visit.
(__same_types): Move into namespace __detail::__variant.
(__check_visitor_results): Likewise. Use __invoke_result_t and
__get_t.
(__check_visitor_result): Remove.
(visit): Use __visit_result_t for return type.
* testsuite/20_util/variant/100384.cc: New test.
(cherry picked from commit af5b2b911dd80ae9cc87404b7e7ab807cf6655d4)
^ permalink raw reply [flat|nested] 12+ messages in thread
* [Bug libstdc++/100384] Compiling in c++17 mode breaks compilation of functions named visit()
2021-05-02 15:38 [Bug c++/100384] New: Compiling in c++17 mode breaks compilation of functions named visit() aacid at kde dot org
` (7 preceding siblings ...)
2021-05-06 13:06 ` cvs-commit at gcc dot gnu.org
@ 2021-06-18 12:56 ` cvs-commit at gcc dot gnu.org
2021-06-18 14:43 ` cvs-commit at gcc dot gnu.org
2021-06-18 14:46 ` redi at gcc dot gnu.org
10 siblings, 0 replies; 12+ messages in thread
From: cvs-commit at gcc dot gnu.org @ 2021-06-18 12:56 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100384
--- Comment #9 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-10 branch has been updated by Jonathan Wakely
<redi@gcc.gnu.org>:
https://gcc.gnu.org/g:8ad4d9b46944db1be6f1b216b5b8e74bd9f66937
commit r10-9937-g8ad4d9b46944db1be6f1b216b5b8e74bd9f66937
Author: Jonathan Wakely <jwakely@redhat.com>
Date: Tue May 4 12:16:46 2021 +0100
libstdc++: Do not use deduced return type for std::visit [PR 100384]
This avoids errors outside the immediate context when std::visit is an
overload candidate because of ADL, but not actually viable.
The solution is to give std::visit a non-deduced return type. New
helpers are introduced for that, and existing ones refactored slightly.
libstdc++-v3/ChangeLog:
PR libstdc++/100384
* include/std/variant (__get_t): New alias template yielding the
return type of std::get<N> on a variant.
(__visit_result_t): New alias template yielding the result of
std::visit.
(__same_types): Move into namespace __detail::__variant.
(__check_visitor_results): Likewise. Use __invoke_result_t and
__get_t.
(__check_visitor_result): Remove.
(visit): Use __visit_result_t for return type.
* testsuite/20_util/variant/100384.cc: New test.
(cherry picked from commit af5b2b911dd80ae9cc87404b7e7ab807cf6655d4)
^ permalink raw reply [flat|nested] 12+ messages in thread
* [Bug libstdc++/100384] Compiling in c++17 mode breaks compilation of functions named visit()
2021-05-02 15:38 [Bug c++/100384] New: Compiling in c++17 mode breaks compilation of functions named visit() aacid at kde dot org
` (8 preceding siblings ...)
2021-06-18 12:56 ` cvs-commit at gcc dot gnu.org
@ 2021-06-18 14:43 ` cvs-commit at gcc dot gnu.org
2021-06-18 14:46 ` redi at gcc dot gnu.org
10 siblings, 0 replies; 12+ messages in thread
From: cvs-commit at gcc dot gnu.org @ 2021-06-18 14:43 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100384
--- Comment #10 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-9 branch has been updated by Jonathan Wakely
<redi@gcc.gnu.org>:
https://gcc.gnu.org/g:91d29ed563bd7e787921f997ea2f80cd87ee59b2
commit r9-9592-g91d29ed563bd7e787921f997ea2f80cd87ee59b2
Author: Jonathan Wakely <jwakely@redhat.com>
Date: Tue May 4 12:16:46 2021 +0100
libstdc++: Do not use deduced return type for std::visit [PR 100384]
This avoids errors outside the immediate context when std::visit is an
overload candidate because of ADL, but not actually viable.
The solution is to give std::visit a non-deduced return type. New
helpers are introduced for that.
libstdc++-v3/ChangeLog:
PR libstdc++/100384
* include/std/variant (__get_t): New alias template yielding the
return type of std::get<N> on a variant.
(__visit_result_t): New alias template yielding the result of
std::visit.
(__do_visit): Use __get_t.
(visit): Use __visit_result_t for return type.
* testsuite/20_util/variant/100384.cc: New test.
(cherry picked from commit af5b2b911dd80ae9cc87404b7e7ab807cf6655d4)
^ permalink raw reply [flat|nested] 12+ messages in thread
* [Bug libstdc++/100384] Compiling in c++17 mode breaks compilation of functions named visit()
2021-05-02 15:38 [Bug c++/100384] New: Compiling in c++17 mode breaks compilation of functions named visit() aacid at kde dot org
` (9 preceding siblings ...)
2021-06-18 14:43 ` cvs-commit at gcc dot gnu.org
@ 2021-06-18 14:46 ` redi at gcc dot gnu.org
10 siblings, 0 replies; 12+ messages in thread
From: redi at gcc dot gnu.org @ 2021-06-18 14:46 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100384
Jonathan Wakely <redi at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |RESOLVED
Resolution|--- |FIXED
Target Milestone|--- |9.5
--- Comment #11 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Fixed for 9.5, 10.4 and 11.2
^ permalink raw reply [flat|nested] 12+ messages in thread
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2021-05-02 15:38 [Bug c++/100384] New: Compiling in c++17 mode breaks compilation of functions named visit() aacid at kde dot org
2021-05-02 15:38 ` [Bug c++/100384] " aacid at kde dot org
2021-05-03 12:59 ` [Bug libstdc++/100384] " aacid at kde dot org
2021-05-03 14:08 ` redi at gcc dot gnu.org
2021-05-03 14:44 ` ppalka at gcc dot gnu.org
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