Re: question about nullptr

On 07/07/2024 05:55, Lawrence D'Oliveiro wrote:

On Sat, 6 Jul 2024 14:51:19 +0100, bart wrote:
 

Using actual zero for a pointer value is crass. This wouldn't work for
example:
>
     char *p = 3;

 But of course this does:
      char *p = 0;
  From the C23 spec, I found this footnote in §6.6:
      A named constant or compound literal constant of integer type and
     value zero is a null pointer constant. A named constant or
     compound literal constant with a pointer type and a value null is
     a null pointer but not a null pointer constant; it may only be
     used to initialize a pointer object if its type implicitly
     converts to the target type.
 That first sentence is so important, you’d think it would be in the main
text somewhere.

It doesn't tell the full story, as you can have any arbitrary expression of such terms that results in a suitable value:
      char* p = width*height;
This is valid if width/height are enums and that area calculation yields zero. But update values slightly and it no longer compiles.