What are valid arguments for localtime function?

Question

I have a code here which uses localtime function. But for some values of its input argument, the code crashes (null pointer returned). I want to know about the allowable range for its input.

#include <stdio.h>
#include <time.h>

int main ()
{
  time_t rawtime;
  struct tm g;
  struct tm *gp;
  __int64 tim;

  tim = 7476811632013133299LL; // I know it's a weird number but valid for time_t
  rawtime = tim / 1000LL;
  gp = localtime(&rawtime);
  printf("Pointer gp = %p\n", gp);

  g = *gp; // this crahses because gp = NULL

  return 0;
}

So what can be said about the allowable range of input to localtime function?

Answer 1

The allowable range is not specified by the C standard.

Quoting the N1570 draft:

The localtime function returns a pointer to the broken-down time, or a null pointer if the specified time cannot be converted to local time.

You should check whether the result is NULL before trying to dereference it.