[Bug c++/94510] [9/10 Regression] nullptr_t implicitly cast to zero twice in std::array

["msebor at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94510

Martin Sebor <msebor at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Assignee|unassigned at gcc dot gnu.org      |msebor at gcc dot gnu.org
             Status|NEW                         |ASSIGNED

--- Comment #9 from Martin Sebor <msebor at gcc dot gnu.org> ---
The changed code in reshape_init_array_1 checks for integer/pointer mismatches
via the following test:

      /* Pointers initialized to strings must be treated as non-zero
         even if the string is empty.  */
      tree init_type = TREE_TYPE (elt_init);
      if (POINTER_TYPE_P (elt_type) != POINTER_TYPE_P (init_type)
          || !type_initializer_zero_p (elt_type, elt_init))
        last_nonzero = index;

...and a test case involving an ordinary pointer is diagnosed:

$ cat t.C && gcc -S -Wall t.C
int a[2] = { nullptr };
int b[2] = { (void*)0 };

t.C:2:23: error: invalid conversion from ‘void*’ to ‘int’ [-fpermissive]
    2 | int b[2] = { (void*)0 };
      |                       ^
      |                       |
      |                       void*


but a nullptr use is not.

(gdb) p debug_tree (init_type)
$6 = (tree) 0x7fffea9521f8
<nullptr_type 0x7fffea9521f8 decltype(nullptr) public unsigned DI
    size <integer_cst 0x7fffea7f7e70 type <integer_type 0x7fffea8150a8
bitsizetype> constant 64>
    unit-size <integer_cst 0x7fffea7f7e88 type <integer_type 0x7fffea815000
sizetype> constant 8>
    align:64 warn_if_not_align:0 symtab:0 alias-set -1 canonical-type
0x7fffea9521f8>

I would expect POINTER_TYPE_P (init_type) to be non-zero but it's not:

(gdb) p POINTER_TYPE_P (init_type)
$7 = false