pointers, functions, and uniform call syntax

[Artur Skawina]

On 09/06/12 22:07, Era Scarecrow wrote:
> On Thursday, 6 September 2012 at 12:00:05 UTC, Artur Skawina wrote:
>> On 09/06/12 13:34, Era Scarecrow wrote:
>>> Alright let's go the opposite direction. Give me an example in which passing a variable (by reference to a function) would EVER require it to check the address to see if it was null. Class/allocated objects should fail before the function gets control. ie:
>>>
>>>  void func(ref int i);
>>>
>>>  class X {
>>>    int i;
>>>  }
>>>
>>>  X x;
>>>  int* i;
>>>  int[10] a;
>>>
>>>  func(x.i); /*should fail while dereferencing x to access i,
>>>               so never gets to func*/
>>>  func(*i);  //does this count as a lvalue? Probably not,
>>>  func(a[0]);//none of these three should compile with that in mind
>>>  func(0);
>>>
>>> Being named variables, and likely non-classes you are then left with mostly local variables, or arrays, or some type of pointer indirection issue. But ever case I come up with says it would fail before the function was called.
>>
>> Both '*i' and 'a[0]' count. (Even '0' could be made to work as a 'const ref' arg, but i'm not sure if that would be a good idea)
> 
>  I wasn't sure about *i. I can see it going either way. *i would need to be dereferenced first, a[0] would need a bounds check which then ensures it exists (even if it was dynamic); So checking an address from ref wouldn't be needed in the func.

No, '*i' does not actually dereference the pointer when used as
a ref argument.

This program won't assert

   auto func(ref int i) { assert(!&i); }
   void main() { int* i; func(*i); }

and would segfault if 'i' was accessed by 'func'.

artur