[Bug c/110238] [10/11/12/13/14 Regression] Incorrect "comparison between pointer and zero character constant" warning when comparing pointer to unsigned null pointer constant

[pinskia at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110238

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |10.5
     Ever confirmed|0                           |1
   Last reconfirmed|                            |2023-06-13
            Summary|Incorrect "comparison       |[10/11/12/13/14 Regression]
                   |between pointer and zero    |Incorrect "comparison
                   |character constant" warning |between pointer and zero
                   |when comparing pointer to   |character constant" warning
                   |unsigned null pointer       |when comparing pointer to
                   |constant                    |unsigned null pointer
                   |                            |constant
             Status|UNCONFIRMED                 |NEW

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Confirmed, introduced with r7-5677-ga9342885b149 .

So I think the issue is in char_type_p we have:
```
static bool
char_type_p (tree type)
{
  return (type == char_type_node
         || type == unsigned_char_type_node
         || type == signed_char_type_node
         || type == char16_type_node
         || type == char32_type_node);
}
```

In C, there is no distinct type for char32_type_node so it is the same as
unsigned here and it returns true for that case .