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* [Bug c++/108234] New: GCC accepts invalid program involving nontype template parameter of auto with non constexpr variable
@ 2022-12-27 13:54 jlame646 at gmail dot com
2022-12-28 19:22 ` [Bug c++/108234] " pinskia at gcc dot gnu.org
` (3 more replies)
0 siblings, 4 replies; 5+ messages in thread
From: jlame646 at gmail dot com @ 2022-12-27 13:54 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108234
Bug ID: 108234
Summary: GCC accepts invalid program involving nontype template
parameter of auto with non constexpr variable
Product: gcc
Version: 13.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: jlame646 at gmail dot com
Target Milestone: ---
GCC trunk accepts the following invalid program:
https://godbolt.org/z/h5q7589Tr
```
template <int&> struct X{};
template <auto V> int func(X<V>) { return 1; }
int i;
int main() { return func(X<i>{}); }
```
Clang rejects the above program while gcc and msvc accepts it.
^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug c++/108234] GCC accepts invalid program involving nontype template parameter of auto with non constexpr variable
2022-12-27 13:54 [Bug c++/108234] New: GCC accepts invalid program involving nontype template parameter of auto with non constexpr variable jlame646 at gmail dot com
@ 2022-12-28 19:22 ` pinskia at gcc dot gnu.org
2022-12-28 19:35 ` pinskia at gcc dot gnu.org
` (2 subsequent siblings)
3 siblings, 0 replies; 5+ messages in thread
From: pinskia at gcc dot gnu.org @ 2022-12-28 19:22 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108234
--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
If I change func to:
template <auto &V> int func(X<V>) { return 1; }
And then clang accepts it.
The question becomes what can be deduced as the type of V.
Here is a slightly different testcase:
```
template <int&> struct X{};
template <typename T>
void ff(){};
template <typename T, T V> int func(X<V>) { return 1; }
int i;
int main() { return func(X<i>{}); }
```
Note GCC rejects the above testcase for C++14 but accepts it for C++17.
So I am not 100% this is invalid and clang just does not implement some rule of
C++17 correctly dealing with reference types ...
^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug c++/108234] GCC accepts invalid program involving nontype template parameter of auto with non constexpr variable
2022-12-27 13:54 [Bug c++/108234] New: GCC accepts invalid program involving nontype template parameter of auto with non constexpr variable jlame646 at gmail dot com
2022-12-28 19:22 ` [Bug c++/108234] " pinskia at gcc dot gnu.org
@ 2022-12-28 19:35 ` pinskia at gcc dot gnu.org
2022-12-28 19:37 ` pinskia at gcc dot gnu.org
2022-12-28 19:38 ` pinskia at gcc dot gnu.org
3 siblings, 0 replies; 5+ messages in thread
From: pinskia at gcc dot gnu.org @ 2022-12-28 19:35 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108234
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |RESOLVED
Resolution|--- |INVALID
--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0127r2.html
Looks like clang does not implement this paper correctly for reference types
...
Modified testcase from that paper using reference types, C++17 should reject
this while c++14 will accept it:
template <const int &N> struct A;
template <typename T, T N> int foo(A<N> *) = delete;
void foo(void *);
constexpr int t = 1;
void bar(A<t> *p) {
foo(p); // ill-formed; previously well-formed
}
^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug c++/108234] GCC accepts invalid program involving nontype template parameter of auto with non constexpr variable
2022-12-27 13:54 [Bug c++/108234] New: GCC accepts invalid program involving nontype template parameter of auto with non constexpr variable jlame646 at gmail dot com
2022-12-28 19:22 ` [Bug c++/108234] " pinskia at gcc dot gnu.org
2022-12-28 19:35 ` pinskia at gcc dot gnu.org
@ 2022-12-28 19:37 ` pinskia at gcc dot gnu.org
2022-12-28 19:38 ` pinskia at gcc dot gnu.org
3 siblings, 0 replies; 5+ messages in thread
From: pinskia at gcc dot gnu.org @ 2022-12-28 19:37 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108234
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
See Also| |https://github.com/llvm/llv
| |m-project/issues/40328
--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
See:
https://github.com/llvm/llvm-project/issues/40328
^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug c++/108234] GCC accepts invalid program involving nontype template parameter of auto with non constexpr variable
2022-12-27 13:54 [Bug c++/108234] New: GCC accepts invalid program involving nontype template parameter of auto with non constexpr variable jlame646 at gmail dot com
` (2 preceding siblings ...)
2022-12-28 19:37 ` pinskia at gcc dot gnu.org
@ 2022-12-28 19:38 ` pinskia at gcc dot gnu.org
3 siblings, 0 replies; 5+ messages in thread
From: pinskia at gcc dot gnu.org @ 2022-12-28 19:38 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108234
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
See Also| |https://github.com/llvm/llv
| |m-project/issues/38721
--- Comment #4 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Also:
https://github.com/llvm/llvm-project/issues/38721
^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2022-12-28 19:38 UTC | newest]
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2022-12-27 13:54 [Bug c++/108234] New: GCC accepts invalid program involving nontype template parameter of auto with non constexpr variable jlame646 at gmail dot com
2022-12-28 19:22 ` [Bug c++/108234] " pinskia at gcc dot gnu.org
2022-12-28 19:35 ` pinskia at gcc dot gnu.org
2022-12-28 19:37 ` pinskia at gcc dot gnu.org
2022-12-28 19:38 ` pinskia at gcc dot gnu.org
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