What does void casting do?

问题

I was reading some source code, and this came up;

struct Cookie *
Curl_cookie_add(struct SessionHandle *data, /* rest of params were here */)
{
/* unrelated things were here */
#ifdef CURL_DISABLE_VERBOSE_STRINGS
  (void)data;
#endif
/* rest of function goes here */
}

As you can see, void casted pointer, isn't even assigned to a variable. I was wondering what is the purpose of this.

回答1:

This cast suppresses a compiler warning that would arise if data is not used.

GCC produces this warning if the -Wunused-parameter flag (implied by -Wextra) is enabled.

回答2:

Fair point Joey - but suppressing that warning also suppresses it for all the cases where the programmer has accidentally not used a parameter...

来源：https://stackoverflow.com/questions/10767933/what-does-void-casting-do