[Bug c++/107222] New: const qualifier appears in mangled NTTP value when the original object is so qualified

[Bug c++/107222] New: const qualifier appears in mangled NTTP value when the original object is so qualified

[johelegp at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107222

            Bug ID: 107222
           Summary: const qualifier appears in mangled NTTP value when the
                    original object is so qualified
           Product: gcc
           Version: 13.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: johelegp at gmail dot com
                CC: johelegp at gmail dot com
  Target Milestone: ---

See https://compiler-explorer.com/z/63f9sxnec.

```C++
struct A { int i; };
union Y { A a; };
constexpr Y make_y(const A a) { return {a}; }
template<auto> struct q { };
template<auto V> constexpr q<V> make_q() { return {}; }
template<auto> void print();
int main() {
  constexpr q x = make_q<make_y({1})>();
  print<x>();
  // +x;
}
```

```
main:
        sub     rsp, 8
        call    void print<q<Y{.a=A const{1}}>{}>()
        xor     eax, eax
        add     rsp, 8
        ret
```

Alternatively, when uncommenting `+x;`:
```
<source>: In function 'int main()':
<source>:10:3: error: no match for 'operator+' (operand type is 'const
q<Y{const A{1}}>')
   10 |   +x;
      |   ^~
```

[Bug c++/107222] const qualifier appears in mangled NTTP value when the original object is so qualified

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107222

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
     Ever confirmed|0                           |1
   Last reconfirmed|                            |2022-10-11
             Status|UNCONFIRMED                 |NEW
           Keywords|                            |ABI, wrong-code

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Here is one which shows the issue at link time.
This should link and run.
One testcase:
```
struct A { int i; };
union Y { A a; };
constexpr Y make_y(const A a) { return {a}; }
template<auto> struct q { };
template<auto V> constexpr q<V> make_q() { return {}; }
template<auto> void print();
template<> void print<q<(Y){.a={1}}>{}>()
{
}
int main() {
  constexpr q x = make_q<make_y({1})>();
  constexpr q x1 = make_q<(Y){.a={1}}>();
  print<x>();
  print<x1>();
}
```
Another one:
```
struct A { int i; };
union Y { A a; };
constexpr Y make_y(const A a) { return {a}; }
template<auto> struct q { };
template<auto V> constexpr q<V> make_q() { return {}; }
void print(q<(Y){.a={1}}> a)
{

}
void print(...);
int main() {
  constexpr q x = make_q<make_y({1})>();
  constexpr q x1 = make_q<(Y){.a={1}}>();
  print(x);
  print(x1);
}
```
clang mangles both x and x1 the same ...