[gnutls-devel] GnuTLS | gnutls_memset: use explicit_bzero (d087db43)

[Development of GNU's TLS library]

Nikos Mavrogiannopoulos commented on a discussion on lib/safe-memfuncs.c:

>   * 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);

According to manpage:
```
It differs from bzero() in that it guarantees that compiler optimizations will not remove the erase operation if the compiler deduces that the operation is "unnecessary".
```
Implementation wise it adds a barrier after memset().
https://code.woboq.org/userspace/glibc/string/explicit_bzero.c.html


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