lifetime of local variables

[Anargyros L. Papadopoulos]

int do_sth(int);

int fun_1(int *val, int i = 0)
{
static int *s[3];

if (val && i >= 0 && i < 3) {
s = val;
return 1;
} else {
if (s[0])
do_sth(*s[0]);
return 0;
}
}

int fun_2(void)
{
int v1 = 1, v2 = 2, v3 = 3;

fun_1(&v1, 0);
fun_1(&v2, 1);
fun_1(&v3, 2);


/* ... code ... */

return fun_1(0); // <<<< HERE >>>>
}

- is it guarantee that in the last call of 'fun_1' (return statement)
pointers to v1, v2, v3, that stored into 's' in 'fun_1', are still valid ?
- if yes, any comment is it guarantee and after optimization ??

 

[Victor Bazarov]

int do_sth(int);

int fun_1(int *val, int i = 0)
{
static int *s[3];

if (val && i >= 0 && i < 3) {
s = val;
return 1;
} else {
if (s[0])
do_sth(*s[0]);
return 0;
}
}

int fun_2(void)
{
int v1 = 1, v2 = 2, v3 = 3;

fun_1(&v1, 0);
fun_1(&v2, 1);
fun_1(&v3, 2);


/* ... code ... */

return fun_1(0); // <<<< HERE >>>>
}

- is it guarantee that in the last call of 'fun_1' (return statement)
pointers to v1, v2, v3, that stored into 's' in 'fun_1', are still valid ?
- if yes, any comment is it guarantee and after optimization ??

AFA the Standard goes, yes, it's still valid. 'v1', 'v2', 'v3' all live
until the block where they are declared (function body) ends. It does not
end with the 'return' statement executing. It ends when function exits.
Since the evaluation of the return statement expression has to complete
before the function exits, the static pointer array contents inside the
'fun_1' are still valid.

V