[Bug c++/107151] New: Specializing a concepted template can emit bogus assembly

[Bug c++/107151] New: Specializing a concepted template can emit bogus assembly

[blubban at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107151

            Bug ID: 107151
           Summary: Specializing a concepted template can emit bogus
                    assembly
           Product: gcc
           Version: 13.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: blubban at gmail dot com
  Target Milestone: ---

#include <cstdio>
#include <concepts>

template <typename T>
void fun(T);

template <>
void fun(char c)
{
    std::puts("foo<char>()");
}

template <std::integral I>
void fun(I i)
{
    std::puts("foo<std::integral>()");
}

int main()
{
    fun<char>(' ');
}

Compile with -std=c++20.

Result:
/tmp/cctfBAWi.s: Assembler messages:
/tmp/cctfBAWi.s:63: Error: symbol `_Z3funIcEvT_' is already defined
/tmp/cctfBAWi.s: Error: .size expression for _Z3funIcEvT_ does not evaluate to
a constant

Expected: Prints foo<char>(), or at least a less cryptic error. With -O2, GCC
only emits one _Z3funIcEvT_, but the resulting program prints
foo<std::integral>().

https://godbolt.org/z/axvdbK1Eh

Clang and MSVC have similar bugs:
https://github.com/llvm/llvm-project/issues/58142
https://developercommunity.visualstudio.com/t/Template-explicit-specializationconcept/10012835

[Bug c++/107151] Specializing a concepted template can emit bogus assembly

[marxin at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107151

Martin Liška <marxin at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2022-10-05
                 CC|                            |marxin at gcc dot gnu.org
     Ever confirmed|0                           |1

--- Comment #1 from Martin Liška <marxin at gcc dot gnu.org> ---
Note clang rejects the code:

clang++ pr107151.C -c -std=c++20 -S
pr107151.C:14:6: error: definition with same mangled name '_Z3funIcEvT_' as
another definition
void fun(I i)
     ^
pr107151.C:8:6: note: previous definition is here
void fun(char c)
     ^
1 error generated.

[Bug c++/107151] Specializing a concepted template can emit bogus assembly

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107151

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
I think this is PR 100825