#include <malloc.h>
#include <stdlib.h>

int main ( void )
{
  int *x = NULL;
  int *y = ( int * ) malloc ( sizeof ( int ) );

  *x = 1;      //违背1

  free ( x );  //违背2
  free ( y );
  free ( y );  //违背3

  return ( 0 );
}