[PATCH] don't trim empty string initializers for pointers (PR 90947)

[Jason Merrill]

On 6/21/19 8:05 PM, Martin Sebor wrote:
> The solution we implemented in GCC 9 to get the mangling of
> non-type template arguments of class types containing array
> members consistent regardless of the form of their
> initialization introduced a couple of bugs.  One of these
> is the subject of this patch.  The bug results in stripping
> trailing initializers for array elements that involve the empty
> string such as in here:
> 
>  Â  void f (void)
>  Â  {
>  Â Â Â  const char* a[1][1] = { "" };
>  Â Â Â  if (!a[0][0])
>  Â Â Â Â Â  __builtin_abort ();
>  Â  }
> 
> The problem is caused by relying on initializer_zerop() that
> returns true for the empty string regardless of whether it's
> used to initialize an array or a pointer (the function doesn't
> know what the initializer is being used for).

Why doesn't the existing POINTER_TYPE_P check handle this?  It's clearly 
intended to.

Jason