[gnutls-help] gnutls_memset: use explicit_bzero

[Maciej S. Szmigiero]

> That is, use the glibc function when available and the second
> parameter is zero.
> 
> Resolves #230
> 
> Signed-off-by: Nikos Mavrogiannopoulos <nmav at redhat.com>
> ---(..)
> --- a/lib/safe-memfuncs.c
> +++ b/lib/safe-memfuncs.c
> @@ -33,14 +30,18 @@
>   * This function will operate similarly to memset(), but will
>   * not be optimized out by the compiler.
>   *
> - * Returns: void.
> - *
>   * Since: 3.4.0
>   **/
>  void gnutls_memset(void *data, int c, size_t size)
>  {
> -	volatile unsigned volatile_zero = 0;
> +	volatile unsigned volatile_zero;
>  	volatile char *vdata = (volatile char*)data;
> +#ifdef HAVE_EXPLICIT_BZERO
> +	if (c == 0) {
> +		explicit_bzero(data, size);

Shouldn't the function return here?

Because otherwise it is doing the zeroing twice:
first time via explicit_bzero(),
second time via a volatile trick below.

> +	}
> +#endif
> +	volatile_zero = 0;
>  
>  	/* This is based on a nice trick for safe memset,
>  	 * sent by David Jacobson in the openssl-dev mailing list.

Maciej