+
+/* If P is null, allocate a block of at least *PN bytes; otherwise,
+ reallocate P so that it contains more than *PN bytes. *PN must be
+ nonzero unless P is null. Set *PN to the new block's size, and
+ return the pointer to the new block. *PN is never set to zero, and
+ the returned pointer is never null. */
+
+void *
+x2realloc (void *p, size_t *pn)
+{
+ return x2nrealloc (p, pn, 1);
+}
+
+/* Allocate S bytes of zeroed memory dynamically, with error checking.
+ There's no need for xnzalloc (N, S), since it would be equivalent
+ to xcalloc (N, S). */
+
+void *
+xzalloc (size_t s)
+{
+ return memset (xmalloc (s), 0, s);
+}
+
+/* Allocate zeroed memory for N elements of S bytes, with error
+ checking. S must be nonzero. */
+
+void *
+xcalloc (size_t n, size_t s)
+{
+ void *p;
+ /* Test for overflow, since some calloc implementations don't have
+ proper overflow checks. But omit overflow and size-zero tests if
+ HAVE_GNU_CALLOC, since GNU calloc catches overflow and never
+ returns NULL if successful. */
+ if ((! HAVE_GNU_CALLOC && xalloc_oversized (n, s))
+ || (! (p = calloc (n, s)) && (HAVE_GNU_CALLOC || n != 0)))
+ xalloc_die ();
+ return p;
+}
+
+/* Clone an object P of size S, with error checking. There's no need
+ for xnmemdup (P, N, S), since xmemdup (P, N * S) works without any
+ need for an arithmetic overflow check. */
+
+void *
+xmemdup (void const *p, size_t s)
+{
+ return memcpy (xmalloc (s), p, s);
+}
+
+/* Clone STRING. */
+
+char *
+xstrdup (char const *string)
+{
+ return xmemdup (string, strlen (string) + 1);
+}