int mallopt (int param, int value);

struct mallinfo mallinfo (void);

struct mallinfo {
  int arena;     // Allocated space except mapped regions
  int ordblks;   // Number of free blocks except fast bins
  int smblks;    // Number of free fast bins
  int hblks;     // Number of mapped regions
  int hblkhd;    // Space in mapped regions
  int usmblks;   // Maximum space allocated so far (only when single thread)
  int fsmblks;   // Space in free fast bins
  int uordblks;  // Total allocated space
  int fordblks;  // Total free space
  int keepcost;  // Space at heap end that can be released
};