How to find out if the C function works for free?

I saw some differences as a result of the following code:

#include <stdio.h>
#include <malloc.h>
#include <string.h>

int main(void)
{
 char* ptr;
 ptr = (char*)malloc(sizeof(char) * 12);
 strcpy(ptr, "Hello World");

 printf("%s\n", ptr);
 printf("FREEING ?\n");

 free(ptr);

 printf("%s\n", ptr);
}

Let me explain:

In the third OSfree printf call, I get different results, gargabge characters on Windows, nothing on Linux and on the Unix system "Hello World" is printed.

Is there a way to check the status of a pointer to find out when the memory was freed?

I think this printing mechanism cannot be trusted all the time.

Thnaks.

Hey.