C Pointer casting: single int pointer to double char pointer -

C Pointer casting: single int pointer to double char pointer -

i trying following, not give me compilation error gives me segmentation fault when run this.

int main(){ int * ptr; *ptr = 254; char **ch = (char **)ptr; printf("\n%x\n",**ch); }

i want know if legal, , if does.

*(char **)ptr

where ptr either of type int or type void

*ptr = 254; here ptr not allocated memory, that's why producing segmentation fault.

first need allocate memory ptr, can set value *ptr.

next, *(char **)ptr not legal (neither char **ch = (char **)ptr;, btw). if compile warnings enabled, you'll warning message

warning: initialization incompatible pointer type

you can easlity understand if seek analyze info type of either variables. consider sample code

#include <stdio.h> #include <stdlib.h> int main(){ int * ptr = malloc(4); *ptr = 254; char **ch = (char **)ptr; printf("\n%x\n",**ch); }

to check, if compile , step through debugger, can see,

5 int * ptr = malloc(4); (gdb) s 6 *ptr = 254; (gdb) 7 char **ch = (char **)ptr; (gdb) p ptr $1 = (int *) 0x804a008 (gdb) p ch $2 = (char **) 0xa7c600 (gdb) p *ch $3 = 0x57e58955 <address 0x57e58955 out of bounds> (gdb) p **ch cannot access memory @ address 0x57e58955

c pointers