extern const char *program_name;
+/* Returns the number of elements in ARRAY. */
#define ARRAY_SIZE(ARRAY) (sizeof ARRAY / sizeof *ARRAY)
-#define ROUND_UP(X, Y) (((X) + ((Y) - 1)) / (Y) * (Y))
+
+/* Returns X / Y, rounding up. X must be nonnegative to round correctly. */
+#define DIV_ROUND_UP(X, Y) (((X) + ((Y) - 1)) / (Y))
+
+/* Returns X rounded up to the nearest multiple of Y. */
+#define ROUND_UP(X, Y) (DIV_ROUND_UP(X, Y) * (Y))
+
+/* Returns X rounded down to the nearest multiple of Y. */
#define ROUND_DOWN(X, Y) ((X) / (Y) * (Y))
+
+/* Returns true if X is a power of 2, otherwise false. */
#define IS_POW2(X) ((X) && !((X) & ((X) - 1)))
#ifndef MIN
void out_of_memory(void) NO_RETURN;
void *xmalloc(size_t) MALLOC_LIKE;
void *xcalloc(size_t, size_t) MALLOC_LIKE;
+void *xzalloc(size_t) MALLOC_LIKE;
void *xrealloc(void *, size_t);
void *xmemdup(const void *, size_t) MALLOC_LIKE;
char *xmemdup0(const char *, size_t) MALLOC_LIKE;