On Sun, Aug 1, 2021 at 2:56 PM Uecker, Martin via Liaison <liaison@lists.isocpp.org> wrote:

Would the following example change behavior?

void foo(void)
{
void* b[3];
void* a[1][3] = { b };
}

Yes - I guess so.

Is the initialization of 'a' ill-formed in C++? g++ rejects it with:

 error: array must be initialized with a brace-enclosed initializer
    4 |   const void* a[1][3] = { b };
      |                           ^

(it's accepted by clang++ and msvc, though, in pedantic/non-permissive mode)
(on adding another brace it is accepted by all 3).

There's a similar case with array-of-bool:

    #include <stdbool.h>

    void foo(void)
    {
      bool b[3];
      bool a[2][3] = { b };
    }

Now, gcc accepts with no warning (gcc -std=c2x -pedantic -Werror)

and clang rejects with -Werror because it diagnoses:

error: address of array 'b' will always evaluate to 'true'
      [-Werror,-Wpointer-bool-conversion]
  bool a[2][3] = { b };
                   ^