[Bug c++/113306] New: constexpr cast from void* fails with typeid result target

[pkeir at outlook dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113306

            Bug ID: 113306
           Summary: constexpr cast from void* fails with typeid result
                    target
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: pkeir at outlook dot com
  Target Milestone: ---

The C++26 code below fails to compile with GCC trunk; with Clang it passes. The
error message indicates that the constexpr evaluator uses `const
__fundamental_type_info_pseudo_2` as the type of `typeid(int)`. (See
https://godbolt.org/z/1Mr9ao9hr.)

#include <typeinfo>
#include <cassert>

constexpr bool test1()
{
  const void* cvp = &typeid(int);

  return static_cast<const std::type_info*>(cvp) != nullptr;
}

int main(int argc, char *argv[])
{
  static_assert(test1());
  assert(test1());
  return 0;
}

The error message is below.

bug3.cpp:13:22:   in ‘constexpr’ expansion of ‘test1()’
bug3.cpp:8:10: error: cast from ‘const void*’ is not allowed in a constant
expression because pointed-to type ‘const __fundamental_type_info_pseudo_2’ is
not similar to ‘const std::type_info’
    8 |   return static_cast<const std::type_info*>(cvp) != nullptr;
      |          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
bug3.cpp:6:32: note: pointed-to object declared here
    6 |   const void* cvp = &typeid(int);