Re: [C++ Patch/RFC] PR 43906

[Jason Merrill <jason at redhat dot com>]

On 08/04/2014 07:01 PM, Paolo Carlini wrote:
> In fact I wondered about that a few minutes after sending my message...
> And this is what I figured out: normally we have hard errors from
> composite_pointer_type (eg, try scalar types, class types), even for
> null values. The only exception I have been able to find earlier today
> is that of pointer to the same function type, eg:
>
> extern void z();
> typedef void (*ptr)();
> void i() { if ( z != (ptr)0 ); }
>
> but in this case the C front-end too doesn't warn.

I don't see why we wouldn't want to warn in this case; it's still the 
case thet the comparison will always be false.

We can also see this situation for non-function pointers:

void f()
{
  int i;
  if (&i != (int*)0);
}

Jason