c - Returning an address of a local pointer variable to main() function -

in following example, function func() returning address of local pointer variable main() function. it's working fine in gcc.

so, is well-defined behaviour?

#include <stdio.h> #include <stdlib.h>  int *func(void);  int *func(void) {    int *p;    p = malloc(sizeof *p);    *p = 10;    return p; }  int main()  {     int *ptr = func();     printf("%d\n",*ptr);     return 0; } 

inside func(), p pointer memory allocated malloc() (or potentially allocated memory, since malloc() can fail, returning null pointer; should checked for). if successful, memory allocation persist until explicitly freed.

the value of p returned calling function, main() in case. p either pointer successful allocation, or null pointer, , returned value (which temporary, , not lvalue) assigned ptr. so, allocated storage can accessed through ptr, copy of value held p before func() returned, though lifetime of p has ended func() has returned.

of course ptr should freed when no longer needed avoid memory leaks. and, there potential undefined behavior here if malloc() fails, since ptr null pointer.