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* [Bug c++/100687] New: [modules, concepts] imported concept gives different result
@ 2021-05-19 22:56 webrown.cpp at gmail dot com
2021-11-25 0:37 ` [Bug c++/100687] " johelegp at gmail dot com
` (2 more replies)
0 siblings, 3 replies; 4+ messages in thread
From: webrown.cpp at gmail dot com @ 2021-05-19 22:56 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100687
Bug ID: 100687
Summary: [modules, concepts] imported concept gives different
result
Product: gcc
Version: 12.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: webrown.cpp at gmail dot com
Target Milestone: ---
Using recent trunk [g++-HEAD (Homebrew GCC HEAD-5380e3c) 12.0.0 20210513],
compiling with significant flags -std=c++23 -fmodules-ts -c.
I have two source files, as follows:
//////////////////////
export module bug_a;
template< class T >
inline constexpr bool probe = false;
//
template< class R, class C >
inline constexpr bool probe<R C::* > = true;
export
template< class T >
concept mbr_ptr = probe<T>;
struct S { int f( ); };
using mf_t = decltype( &S::f );
static_assert( mbr_ptr< mf_t > );
//////////////////////
This bug_a module compiles successfully. In particular, the static_assert
passes.
//////////////////////
export module bug_b;
import bug_a;
struct S { int f( ); };
using mf_t = decltype( &S::f );
static_assert( mbr_ptr< mf_t > );
//////////////////////
This bug_b module does not compile. The diagnostics are reproduced below,
including the somewhat mysterious lone apostrophe:
bug_b.cc:8:16: error: static assertion failed
8 | static_assert( mbr_ptr< mf_t > );
| ^~~~~~~~~~~~~~~
bug_b.cc:8:16: note: constraints not satisfied
'
bug_a.cc:12: confused by earlier errors, bailing out
Please note that the static_assert and supporting declarations in module bug_a
are identical to those in module bug_a, yet one compiles while the other does
not.
Thus we seem to have two problems: (1) the lone apostrophe amongst the
diagnostics, and (2) the inconsistent evaluation of identical expressions.
Finally, please note that if I use a class template (instead of the variable
template) in module bug_a, both modules' static_asserts now compile without
complaint:
//////////////////////
template< class T >
struct probe { static constexpr bool value = false; };
//
template< class R, class C >
struct probe<R C::*> { static constexpr bool value = true; };
export
template< class T >
concept
mbr_ptr = probe<T>::value;
//////////////////////
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug c++/100687] [modules, concepts] imported concept gives different result
2021-05-19 22:56 [Bug c++/100687] New: [modules, concepts] imported concept gives different result webrown.cpp at gmail dot com
@ 2021-11-25 0:37 ` johelegp at gmail dot com
2022-03-23 22:23 ` johelegp at gmail dot com
2022-09-22 12:57 ` ppalka at gcc dot gnu.org
2 siblings, 0 replies; 4+ messages in thread
From: johelegp at gmail dot com @ 2021-11-25 0:37 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100687
Johel Ernesto Guerrero Peña <johelegp at gmail dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |johelegp at gmail dot com
--- Comment #1 from Johel Ernesto Guerrero Peña <johelegp at gmail dot com> ---
I happened upon the same bug when changing a trait to be specialized directly
through the variable template rather than a class template. In my case, I
asserted through the variable template, so I can confirm that it's solely a bug
with modules and not with concepts.
See https://godbolt.org/z/jPT9T6ovP.
mod.cpp:
```C++
export module mod;
export
template< class T >
inline constexpr bool probe = false;
//
template< class R, class C >
inline constexpr bool probe<R C::* > = true;
struct S { int f( ); };
using mf_t = decltype( &S::f );
static_assert( probe< mf_t > );
```
test.cpp:
```C++
import mod;
struct S { int f( ); };
using mf_t = decltype( &S::f );
static_assert( probe< mf_t > );
```
Output:
```
test.cpp:6:16: error: static assertion failed
6 | static_assert( probe< mf_t > );
| ^~~~~~~~~~~~~
```
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug c++/100687] [modules, concepts] imported concept gives different result
2021-05-19 22:56 [Bug c++/100687] New: [modules, concepts] imported concept gives different result webrown.cpp at gmail dot com
2021-11-25 0:37 ` [Bug c++/100687] " johelegp at gmail dot com
@ 2022-03-23 22:23 ` johelegp at gmail dot com
2022-09-22 12:57 ` ppalka at gcc dot gnu.org
2 siblings, 0 replies; 4+ messages in thread
From: johelegp at gmail dot com @ 2022-03-23 22:23 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100687
--- Comment #2 from Johel Ernesto Guerrero Peña <johelegp at gmail dot com> ---
Another use case (Clang: https://godbolt.org/z/hTPsPbEhe) (GCC:
https://godbolt.org/z/96MqTvrKv):
`mod.cpp`:
```C++
export module mod;
export template<class T, class U>
inline constexpr bool is_same_v = false;
export template<class T>
inline constexpr bool is_same_v<T, T> = true;
```
`test.cpp`:
```C++
import mod;
static_assert(is_same_v<int, int>);
int main() {
}
```
Output:
```
test.cpp:2:15: error: static assertion failed
2 | static_assert(is_same_v<int, int>);
| ^~~~~~~~~~~~~~~~~~~
```
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug c++/100687] [modules, concepts] imported concept gives different result
2021-05-19 22:56 [Bug c++/100687] New: [modules, concepts] imported concept gives different result webrown.cpp at gmail dot com
2021-11-25 0:37 ` [Bug c++/100687] " johelegp at gmail dot com
2022-03-23 22:23 ` johelegp at gmail dot com
@ 2022-09-22 12:57 ` ppalka at gcc dot gnu.org
2 siblings, 0 replies; 4+ messages in thread
From: ppalka at gcc dot gnu.org @ 2022-09-22 12:57 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100687
Patrick Palka <ppalka at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |ppalka at gcc dot gnu.org
Status|UNCONFIRMED |RESOLVED
Resolution|--- |DUPLICATE
--- Comment #3 from Patrick Palka <ppalka at gcc dot gnu.org> ---
Should be fixed for GCC 13 by the fix for PR106826.
*** This bug has been marked as a duplicate of bug 106826 ***
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2022-09-22 12:57 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2021-05-19 22:56 [Bug c++/100687] New: [modules, concepts] imported concept gives different result webrown.cpp at gmail dot com
2021-11-25 0:37 ` [Bug c++/100687] " johelegp at gmail dot com
2022-03-23 22:23 ` johelegp at gmail dot com
2022-09-22 12:57 ` ppalka at gcc dot gnu.org
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