[PATCH] malloc/malloc.c: Avoid calling sbrk unnecessarily with zero

[Siddhesh Poyarekar]

On Fri, Jun 13, 2014 at 04:41:44PM +0100, Will Newton wrote:
> Due to my bad review suggestion for the fix for BZ #15089 a check
> was removed from systrim to prevent sbrk being called with a zero
> argument. Add the check back to avoid this useless work.
> 
> ChangeLog:
> 
> 2014-06-13  Will Newton  <will.newton@linaro.org>
> 
> 	* malloc/malloc.c (systrim): If extra is zero then return
> 	early.

Looks good to me.

Siddhesh

> ---
>  malloc/malloc.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/malloc/malloc.c b/malloc/malloc.c
> index d8fd8b4..41fd76a 100644
> --- a/malloc/malloc.c
> +++ b/malloc/malloc.c
> @@ -2749,6 +2749,9 @@ systrim (size_t pad, mstate av)
>    /* Release in pagesize units, keeping at least one page */
>    extra = (top_area - pad) & ~(pagesz - 1);
>  
> +  if (extra == 0)
> +    return 0;
> +
>    /*
>       Only proceed if end of memory is where we last set it.
>       This avoids problems if there were foreign sbrk calls.
> -- 
> 1.9.3
> 
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