I realize that my example not correct in general. But interesting to find out how it works.
/* C/C++ (gcc-4.3.4) */
#include <stdio.h>
int main() {
/*volatile*/ int i = 5;
int j = 500;
int *p = &j;
printf( "%d %x\n", *p, p );
p++;
printf( "%d %x\n", *p, p ); // works correct with volatile (*p is 5)
//printf( "%d %x\n", *p, &i ); // works correct without volatile
return 0;
}
Is it some kind of optimization?
UPDT Ok i got about UB. I won't hope on another else.
BUT if i have 2 int vars which placed adjacent to each others (see addresses) why this code shouldn't works?
p++;
The code has undefined behavior. Pointer is pointing to some garbage location. Dereferencing it leads to unpredicted results.
What do you call corerct
? It isn't guaranted, how variables will be stored, so ANY
result is correct
Both variables are not necessarly adjacent in memory. You could use an array to do this.
#define PRINT(p) (printf("%i %p\n", *(p), (void *)(p)))
int t[2];
int *a = &t[0];
int *b = &t[1];
*a = 5;
*b = 6;
int *p = a;
PRINT(p);
++p;
PRINT(p);
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