libiberty: avoid reading past end of buffer in strndup/xstrndup (PR c/78498)

gcc/ChangeLog:
	PR c/78498
	* selftest.c (selftest::assert_strndup_eq): New function.
	(selftest::test_strndup): New function.
	(selftest::test_libiberty): New function.
	(selftest::selftest_c_tests): Call test_libiberty.

gcc/testsuite/ChangeLog:
	PR c/78498
	* gcc.dg/format/pr78494.c: New test case.

libiberty/ChangeLog:
	PR c/78498
	* strndup.c (strlen): Delete decl.
	(strnlen): Add decl.
	(strndup): Call strnlen rather than strlen.
	* xstrndup.c (xstrndup): Likewise.

From-SVN: r243030

1 files changed, 48 insertions, 0 deletions

diff --git a/gcc/selftest.c b/gcc/selftest.c
index 2a729be..6df73c2 100644
--- a/gcc/selftest.c
+++ b/gcc/selftest.c
@@ -198,6 +198,53 @@ read_file (const location &loc, const char *path)
   return result;
 }
 
+/* Selftests for libiberty.  */
+
+/* Verify that both strndup and xstrndup generate EXPECTED
+   when called on SRC and N.  */
+
+static void
+assert_strndup_eq (const char *expected, const char *src, size_t n)
+{
+  char *buf = strndup (src, n);
+  if (buf)
+    ASSERT_STREQ (expected, buf);
+  free (buf);
+
+  buf = xstrndup (src, n);
+  ASSERT_STREQ (expected, buf);
+  free (buf);
+}
+
+/* Verify that strndup and xstrndup work as expected.  */
+
+static void
+test_strndup ()
+{
+  assert_strndup_eq ("", "test", 0);
+  assert_strndup_eq ("t", "test", 1);
+  assert_strndup_eq ("te", "test", 2);
+  assert_strndup_eq ("tes", "test", 3);
+  assert_strndup_eq ("test", "test", 4);
+  assert_strndup_eq ("test", "test", 5);
+
+  /* Test on an string without zero termination.  */
+  const char src[4] = {'t', 'e', 's', 't'};
+  assert_strndup_eq ("", src, 0);
+  assert_strndup_eq ("t", src, 1);
+  assert_strndup_eq ("te", src, 2);
+  assert_strndup_eq ("tes", src, 3);
+  assert_strndup_eq ("test", src, 4);
+}
+
+/* Run selftests for libiberty.  */
+
+static void
+test_libiberty ()
+{
+  test_strndup ();
+}
+
 /* Selftests for the selftest system itself.  */
 
 /* Sanity-check the ASSERT_ macros with various passing cases.  */
@@ -245,6 +292,7 @@ test_read_file ()
 void
 selftest_c_tests ()
 {
+  test_libiberty ();
   test_assertions ();
   test_named_temp_file ();
   test_read_file ();