Re: [PATCH] Refactor malloc (x * sizeof (t) to XNMALLOC (x, t).

[OndÅej BÃlka <neleai at seznam dot cz>]

On Thu, Oct 31, 2013 at 01:59:35PM -0700, Paul Eggert wrote:
> On 10/31/2013 09:46 AM, OndÅej BÃlka wrote:
> 
> > +#define XNMALLOC(e, tp) (tp *) malloc ((e) * sizeof (tp))
> 
> Don't we need something similar for realloc?
>
Will come in next iteration.
 
> It needs another parentheses around the entire definiens.
> 
> Better yet, why not a function instead of a macro?

A macro saves cast in more cases than adding cast to change type.

Both approaches are possible but I would prefer sticking to one.

Second reason that I picked macro was because I assumed that gcc does
not inline functions with inline assembly. A gcc does it which changes
situation a bit.

> E.g., something like this in libc-internal.h:
> 
>   /* Return the address of an array of N objects, each of nonzero
>      size S, or NULL (setting errno) if the allocation fails.  */
> 
>   inline void *
>   nmalloc (size_t n, size_t s)
>   {
>     return malloc (n <= SIZE_MAX / s ? n * s : SIZE_MAX);
>   }
> 
> That way, instead of this:
> 
>   result = XNMALLOC (step_cnt, struct __gconv_step);
> 
> a caller can write this:
> 
>   result = nmalloc (step_cnt, sizeof *result);
> 
> with simpler semantics, and with less churn later if 'result' changes
> its type.