Update.

* stdlib/Makefile (tests): Add tst-qsort.
	* stdlib/tst-qsort.c: New file.  Written by Paul Eggert.

stdlib/tst-qsort.c

@@ -0,0 +1,42 @@
+/* Test case by Paul Eggert <eggert@twinsun.com> */
+#include <stdio.h>
+#include <stdlib.h>
+
+struct big { char c[4 * 1024]; };
+
+struct big *array;
+struct big *array_end;
+
+int
+compare (void const *a1, void const *b1)
+{
+  struct big const *a = a1;
+  struct big const *b = b1;
+  if (! (array <= a && a < array_end
+	 && array <= b && b < array_end))
+    {
+      exit (EXIT_FAILURE);
+    }
+  return b->c[0] - a->c[0];
+}
+
+int
+main (int argc, char **argv)
+{
+  size_t i;
+  size_t array_members = argv[1] ? atoi (argv[1]) : 50;
+  array = (struct big *) malloc (array_members * sizeof *array);
+  if (array == NULL)
+    {
+      puts ("no memory");
+      exit (EXIT_FAILURE);
+    }
+
+  array_end = array + array_members;
+  for (i = 0; i < array_members; i++)
+    array[i].c[0] = i % 128;
+
+  qsort (array, array_members, sizeof *array, compare);
+
+  return 0;
+}