Add memmem memcheck tests

Ensure that memmem behaves as expected and doesn't yield memcheck false
positives.

memcheck/tests/Makefile.am

@@ -219,6 +219,7 @@ EXTRA_DIST = \
 	memalign2.stderr.exp memalign2.vgtest \
 	memcmptest.stderr.exp memcmptest.stderr.exp2 \
 	memcmptest.stdout.exp memcmptest.vgtest \
+	memmem.stderr.exp memmem.vgtest \
 	mempool.stderr.exp mempool.vgtest \
 	mempool2.stderr.exp mempool2.vgtest \
 	metadata.stderr.exp metadata.stdout.exp metadata.vgtest \
@@ -417,6 +418,7 @@ check_PROGRAMS = \
 	malloc_usable malloc1 malloc2 malloc3 manuel1 manuel2 manuel3 \
 	match-overrun \
 	memalign_test memalign2 memcmptest mempool mempool2 mmaptest \
+	memmem \
 	mismatches new_override metadata \
 	nanoleak_supp nanoleak2 new_nothrow \
 	noisy_child \

memcheck/tests/memmem.c

@@ -0,0 +1,69 @@
+#define _GNU_SOURCE
+#include <assert.h>
+#include <string.h>
+#include <stdlib.h>
+
+/* mallocs an mem block and fills it with A. A needs to be a zero
+   terminated string. The A string chars, minus the terminating zero
+   are copied into the returned mem block.  */
+static void *
+create_mem (const char *a)
+{
+  size_t len = strlen (a);
+  void *mem = malloc (len);
+  memcpy (mem, a, len);
+  return mem;
+}
+
+int
+main ()
+{
+  char *haystack;
+  char *needle;
+
+  haystack = create_mem ("a");
+  needle = create_mem ("a");
+  assert (memmem (haystack, 0, needle, 0) == haystack);
+  assert (memmem (haystack, 1, needle, 0) == haystack);
+  assert (memmem (haystack, 0, needle, 1) == NULL);
+  assert (memmem (haystack, 1, needle, 1) == haystack);
+  free (haystack);
+  free (needle);
+
+  haystack = create_mem ("abc");
+  needle = create_mem ("bc");
+  assert (memmem (haystack, 3, needle, 0) == haystack);
+  assert (memmem (haystack, 3, needle, 2) == haystack + 1);
+  assert (memmem (haystack + 1, 2, needle, 2) == haystack + 1);
+  assert (memmem (haystack + 2, 1, needle, 2) == NULL);
+  free (haystack);
+  free (needle);
+
+  haystack = create_mem ("abcabcabc");
+  needle = create_mem ("bca");
+  assert (memmem (haystack, 9, needle, 3) == haystack + 1);
+  free (haystack);
+  free (needle);
+
+  haystack = create_mem ("abcabcabc");
+  needle = create_mem ("bcad");
+  assert (memmem (haystack, 9, needle, 4) == NULL);
+  free (haystack);
+  free (needle);
+
+  haystack = create_mem ("xxxxxxxxxxxxxxxxxABC");
+  needle = create_mem ("ABCD");
+  assert (memmem (haystack, 20, needle, 2) == haystack + 17);
+  assert (memmem (haystack + 3, 17, needle, 2) == haystack + 17);
+  assert (memmem (haystack + 15, 5, needle, 2) == haystack + 17);
+  assert (memmem (haystack, 20, needle, 3) == haystack + 17);
+  assert (memmem (haystack + 3, 17, needle, 3) == haystack + 17);
+  assert (memmem (haystack + 15, 5, needle, 3) == haystack + 17);
+  assert (memmem (haystack, 20, needle, 4) == NULL);
+  assert (memmem (haystack + 3, 5, needle, 4) == NULL);
+  assert (memmem (haystack + 15, 5, needle, 4) == NULL);
+  free (haystack);
+  free (needle);
+
+  return 0;
+}

memcheck/tests/memmem.vgtest

@@ -0,0 +1,2 @@
+prog: memmem
+vgopts: -q