Implement strlcpy and strlcat [BZ #178]

These functions are about to be added to POSIX, under Austin Group
issue 986.

The fortified strlcat implementation does not raise SIGABRT if the
destination buffer does not contain a null terminator, it just
inherits the non-failing regular strlcat behavior.

Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>

1 files changed, 84 insertions, 0 deletions

diff --git a/string/tst-strlcat.c b/string/tst-strlcat.c
new file mode 100644
index 0000000000..f8c716373e
--- /dev/null
+++ b/string/tst-strlcat.c
@@ -0,0 +1,84 @@
+/* Test the strlcat function.
+   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 <string.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <support/check.h>
+
+static int
+do_test (void)
+{
+  struct {
+    char buf1[16];
+    char buf2[16];
+  } s;
+
+  /* Nothing is written to the destination if its size is 0.  */
+  memset (&s, '@', sizeof (s));
+  TEST_COMPARE (strlcat (s.buf1, "", 0), 0);
+  TEST_COMPARE_BLOB (&s, sizeof (s), "@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@", 32);
+  TEST_COMPARE (strlcat (s.buf1, "Hello!", 0), 6);
+  TEST_COMPARE_BLOB (&s, sizeof (s), "@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@", 32);
+
+  /* No bytes are are modified in the target buffer if the source
+     string is short enough.  */
+  memset (&s, '@', sizeof (s));
+  strcpy (s.buf1, "He");
+  TEST_COMPARE (strlcat (s.buf1, "llo!", sizeof (s.buf1)), 6);
+  TEST_COMPARE_BLOB (&s, sizeof (s), "Hello!\0@@@@@@@@@@@@@@@@@@@@@@@@@", 32);
+
+  /* A source string which fits exactly into the destination buffer is
+     not truncated.  */
+  memset (&s, '@', sizeof (s));
+  strcpy (s.buf1, "H");
+  TEST_COMPARE (strlcat (s.buf1, "ello, world!!!", sizeof (s.buf1)), 15);
+  TEST_COMPARE_BLOB (&s, sizeof (s),
+		     "Hello, world!!!\0@@@@@@@@@@@@@@@@@@@@@@@@@", 32);
+
+  /* A source string one character longer than the destination buffer
+     is truncated by one character.  The total length is returned.  */
+  memset (&s, '@', sizeof (s));
+  strcpy (s.buf1, "Hello");
+  TEST_COMPARE (strlcat (s.buf1, ", world!!!!", sizeof (s.buf1)), 16);
+  TEST_COMPARE_BLOB (&s, sizeof (s),
+		     "Hello, world!!!\0@@@@@@@@@@@@@@@@@@@@@@@@@", 32);
+
+  /* An even longer source string is truncated as well, and the total
+     length is returned.  */
+  memset (&s, '@', sizeof (s));
+  strcpy (s.buf1, "Hello,");
+  TEST_COMPARE (strlcat (s.buf1, " world!!!!!!!!", sizeof (s.buf1)), 20);
+  TEST_COMPARE_BLOB (&s, sizeof (s),
+		     "Hello, world!!!\0@@@@@@@@@@@@@@@@@@@@@@@@@", 32);
+
+  /* A destination string which is not NUL-terminated does not result
+     in any changes to the buffer.  */
+  memset (&s, '@', sizeof (s));
+  memset (s.buf1, '$', sizeof (s.buf1));
+  TEST_COMPARE (strlcat (s.buf1, "", sizeof (s.buf1)), 16);
+  TEST_COMPARE_BLOB (&s, sizeof (s), "$$$$$$$$$$$$$$$$@@@@@@@@@@@@@@@@", 32);
+  TEST_COMPARE (strlcat (s.buf1, "Hello!", sizeof (s.buf1)), 22);
+  TEST_COMPARE_BLOB (&s, sizeof (s), "$$$$$$$$$$$$$$$$@@@@@@@@@@@@@@@@", 32);
+  TEST_COMPARE (strlcat (s.buf1, "Hello, world!!!!!!!!", sizeof (s.buf1)), 36);
+  TEST_COMPARE_BLOB (&s, sizeof (s), "$$$$$$$$$$$$$$$$@@@@@@@@@@@@@@@@", 32);
+
+  return 0;
+}
+
+#include <support/test-driver.c>