Jeffrey Walton schrieb:
Hi All,
I was looking at some slides on OpenSSL and secure memory wiping using
volatile (Slide 36 at
http://www.slideshare.net/guanzhi/crypto-with-openssl).
I believe GCC's interpretation of the use for 'volatile' is memory
mapped hardware. I think Ian stated it for me some time ago when I was
trying to understand different interpretations among compilers. If
volatile is for memory mapped hardware, why does GCC compile the
following:
volatile void clean_memory(volatile void* dest, size_t len)
{
volatile unsigned char* p;
for(p = (volatile unsigned char*)dest; len; dest[--len] = 0)
;;
}
How does a function become a 'volatile' memory mapped object related
to hardware?
volatile can be used to express that a function is noreturn like in the
following example where only one call of f() is issued:
typedef void ft (void);
volatile ft f;
void foo (void)
{
f();
f();
}
or this example that throws
<stdin>: In function 'f':
<stdin>:4:1: warning: 'noreturn' function does return [enabled by default]
typedef void ft (void);
volatile ft f;
void f (void) {}
In your example, the volatile looks meaningless and like a typo.
Johann
