void foo ( char *msg ) {
  char *p = malloc( 10 );
  if ( strlen(msg) >= 10 ) {
    free( p );
    p = NULL;
  } else {
    strcpy( p, msg );
  }
  return p;
}
 
int main ( ) {
  char *p = foo( "hello" );
  if ( p ) {
    printf( "Yay %s\n", p );
    free( p );
  }
  return 0;
}

struct node
{
    unsigned int line_number;
    char* file;
    void* ptr;
    struct node* next;
};
 
void* mymalloc(unsigned int size, unsigned ine line_number, const char*filename)
{
    void* ptr = malloc(size);
     // now add the pointer to the linked list, not shown 
 
    return ptr;
}
 
void myfree(void* ptr)
{
    // search list for ptr and when (and if) found delete the node
    // code is not shown here
 
    free(ptr);
}
 
int main()
{
     // example use.  Note:  I don't know if all compilers support __LINE__ and
     // __FILE__ macros or not.  __LINE__ is a preprocessor directive that 
     // returns the current line number of the file being compiled, and
     // __FILE__ is a preprocessor directive that returns the file name
     //  of the current file being compiled.
     int* array = mymalloc( sizeof(int * 10), __LINE__, __FILE__);
 
}

void foo ( char *msg ) {
  char *p = malloc( 10 );
  if ( strlen(msg) >= 10 )   -> at this point if free was missed ?
      return;
  else {
    strcpy( p, msg );
  }
  return p;
}
int main ( ) {
  char *p = foo( "hello" );
  if ( p ) {
    printf( "Yay %s\n", p );
    free( p );
  }
  return 0;
}