Pointless use of restrict

[Tim Prince]

Marcus Clyne wrote:
> Hi,
> 
> Am I right in saying that defining a function like
> 
> func_name (my_type_t * __restrict);
> 
> is pointless, because there are no other pointers that the pointer could 
> overlap with?
> 
Maybe, if there are no global variables.
However, __restrict appears to be a BSD version of C99 restrict or gcc 
__restrict__

> Can anyone explain what GCC does differently for the two following 
> definitions:
> 
> func1 (my_type_t * __restrict, my_type_t *__restrict);
> 
> AND
> 
> func2 (my_type_t *, my_type_t *);
> 
> ?
> 

You may need an example relevant to your own usage, where you could 
discover (perhaps by -S or other enabled phase output) what those 
differences are.  One of the more common uses of * restrict is to enable 
auto-vectorization.