string: Add tests for strndup (BZ #30266)

Copy strncpy tests for strndup.  Covers some basic testcases with random
strings.  Remove tests that set the destination's bytes and checked the
resulting buffer's bytes.  Remove wide character test support since
wcsndup() doesn't exist.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

string/Makefile

@@ -163,6 +163,7 @@ tests := \
   test-strncat \
   test-strncmp \
   test-strncpy \
+  test-strndup \
   test-strnlen \
   test-strpbrk \
   test-strrchr \

string/test-strndup.c

@@ -0,0 +1,200 @@
+/* Test strndup functions.
+   Copyright (C) 2023 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <support/check.h>
+
+#define TEST_MAIN
+#include "test-string.h"
+
+static void
+do_one_test (const char *src, size_t len, size_t n)
+{
+  char *dst = strndup (src, n);
+  size_t s = (len > n ? n: len) * sizeof (char);
+
+  TEST_COMPARE_BLOB (dst, s, src, s);
+
+  free (dst);
+}
+
+static void
+do_test (size_t align1, size_t align2, size_t len, size_t n, int max_char)
+{
+  size_t i;
+  char *s1;
+
+  align1 &= 7;
+  if ((align1 + len) * sizeof (char) >= page_size)
+    return;
+
+  align2 &= 7;
+  if ((align2 + len) * sizeof (char) >= page_size)
+    return;
+
+  s1 = (char *) (buf1) + align1;
+
+  for (i = 0; i < len; ++i)
+    s1[i] = 32 + 23 * i % (max_char - 32);
+  s1[len] = 0;
+  for (i = len + 1; (i + align1) * sizeof (char) < page_size && i < len + 64;
+       ++i)
+    s1[i] = 32 + 32 * i % (max_char - 32);
+
+  do_one_test (s1, len, n);
+}
+
+static void
+do_page_tests (void)
+{
+  char *s1;
+  const size_t maxoffset = 64;
+
+  /* Put s1 at the maxoffset from the edge of buf1's last page.  */
+  s1 = (char *) buf1 + BUF1PAGES * page_size / sizeof (char) - maxoffset;
+
+  memset (s1, 'a', maxoffset - 1);
+  s1[maxoffset - 1] = '\0';
+
+  /* Both strings are bounded to a page with read/write access and the next
+     page is protected with PROT_NONE (meaning that any access outside of the
+     page regions will trigger an invalid memory access).
+
+     The loop copies the string s1 for all possible offsets up to maxoffset
+     for both inputs with a size larger than s1 (so memory access outside the
+     expected memory regions might trigger invalid access).  */
+
+  for (size_t off1 = 0; off1 < maxoffset; off1++)
+    for (size_t off2 = 0; off2 < maxoffset; off2++)
+      do_one_test (s1 + off1, maxoffset - off1 - 1,
+		   maxoffset + (maxoffset - off2));
+}
+
+static void
+do_random_tests (void)
+{
+  size_t i, j, n, align1, align2, len, size, mode;
+  char *p1 = (char *) (buf1 + page_size) - 512;
+  char *res;
+
+  for (n = 0; n < ITERATIONS; n++)
+    {
+      mode = random ();
+      if (mode & 1)
+	{
+	  size = random () & 255;
+	  align1 = 512 - size - (random () & 15);
+	  if (mode & 2)
+	    align2 = align1 - (random () & 24);
+	  else
+	    align2 = align1 - (random () & 31);
+	  if (mode & 4)
+	    {
+	      j = align1;
+	      align1 = align2;
+	      align2 = j;
+	    }
+	  if (mode & 8)
+	    len = size - (random () & 31);
+	  else
+	    len = 512;
+	  if (len >= 512)
+	    len = random () & 511;
+	}
+      else
+	{
+	  align1 = random () & 31;
+	  if (mode & 2)
+	    align2 = random () & 31;
+	  else
+	    align2 = align1 + (random () & 24);
+	  len = random () & 511;
+	  j = align1;
+	  if (align2 > j)
+	    j = align2;
+	  if (mode & 4)
+	    {
+	      size = random () & 511;
+	      if (size + j > 512)
+		size = 512 - j - (random () & 31);
+	    }
+	  else
+	    size = 512 - j;
+	  if ((mode & 8) && len + j >= 512)
+	    len = 512 - j - (random () & 7);
+	}
+      j = len + align1 + 64;
+      if (j > 512)
+	j = 512;
+      for (i = 0; i < j; i++)
+	{
+	  if (i == len + align1)
+	    p1[i] = 0;
+	  else
+	    {
+	      p1[i] = random () & CHAR_MAX;
+	      if (i >= align1 && i < len + align1 && !p1[i])
+		p1[i] = (random () & 127) + 3;
+	    }
+	}
+
+	res = (char *) strndup ((char *) (p1 + align1), size);
+	j = len + 1;
+	if (size < j)
+	  j = size;
+	TEST_COMPARE_BLOB (res, j, (char *) (p1 + align1), j);
+	free (res);
+    }
+}
+
+int
+test_main (void)
+{
+  size_t i;
+
+  test_init ();
+
+  printf ("%28s", "");
+  printf ("\t%s", "strndup");
+  putchar ('\n');
+
+  for (i = 1; i < 8; ++i)
+    {
+      do_test (i, i, 16, 16, 127);
+      do_test (i, i, 16, 16, CHAR_MAX);
+      do_test (i, 2 * i, 16, 16, 127);
+      do_test (2 * i, i, 16, 16, CHAR_MAX);
+      do_test (8 - i, 2 * i, 1 << i, 2 << i, 127);
+      do_test (2 * i, 8 - i, 2 << i, 1 << i, 127);
+      do_test (8 - i, 2 * i, 1 << i, 2 << i, CHAR_MAX);
+      do_test (2 * i, 8 - i, 2 << i, 1 << i, CHAR_MAX);
+    }
+
+  for (i = 1; i < 8; ++i)
+    {
+      do_test (0, 0, 4 << i, 8 << i, 127);
+      do_test (0, 0, 16 << i, 8 << i, 127);
+      do_test (8 - i, 2 * i, 4 << i, 8 << i, 127);
+      do_test (8 - i, 2 * i, 16 << i, 8 << i, 127);
+    }
+
+  do_random_tests ();
+  do_page_tests ();
+  return ret;
+}
+
+#include <support/test-driver.c>