--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,12 @@
 2008-04-28  Eric Blake  <ebb9@byu.net>
 
+	Test getndelim2.
+	* modules/getndelim2-tests: New file.
+	* tests/test-getndelim2.c: Likewise.
+	* lib/getndelim2.c (getndelim2): Never return 0.  Lock the
+	stream.
+	* m4/getndelim2.m4 (gl_GETNDELIM2): Check for lock functions.
+
 	* MODULES.html.sh: Document new module.
 
 2008-04-20  Bruno Haible  <bruno@clisp.org>

--- a/lib/getndelim2.c
+++ b/lib/getndelim2.c
@@ -1,7 +1,7 @@
 /* getndelim2 - Read a line from a stream, stopping at one of 2 delimiters,
    with bounded memory allocation.
 
-   Copyright (C) 1993, 1996, 1997, 1998, 2000, 2003, 2004, 2006 Free
+   Copyright (C) 1993, 1996, 1997, 1998, 2000, 2003, 2004, 2006, 2008 Free
    Software Foundation, Inc.
 
    This program is free software: you can redistribute it and/or modify
@@ -29,6 +29,14 @@
 #if USE_UNLOCKED_IO
 # include "unlocked-io.h"
 #endif
+#if !HAVE_FLOCKFILE
+# undef flockfile
+# define flockfile(x) ((void) 0)
+#endif
+#if !HAVE_FUNLOCKFILE
+# undef funlockfile
+# define funlockfile(x) ((void) 0)
+#endif
 
 #include <limits.h>
 #include <stdint.h>
@@ -73,6 +81,8 @@
   if (nbytes_avail == 0 && nmax <= size)
     goto done;
 
+  flockfile (stream);
+
   for (;;)
     {
       /* Here always ptr + size == read_pos + nbytes_avail.  */
@@ -95,14 +105,14 @@
 	    {
 	      size_t newsizemax = offset + GETNDELIM2_MAXIMUM + 1;
 	      if (size == newsizemax)
-		goto done;
+		goto unlock_done;
 	      newsize = newsizemax;
 	    }
 
 	  nbytes_avail = newsize - (read_pos - ptr);
 	  newptr = realloc (ptr, newsize);
 	  if (!newptr)
-	    goto done;
+	    goto unlock_done;
 	  ptr = newptr;
 	  size = newsize;
 	  read_pos = size - nbytes_avail + ptr;
@@ -113,7 +123,7 @@
 	{
 	  /* Return partial line, if any.  */
 	  if (read_pos == ptr)
-	    goto done;
+	    goto unlock_done;
 	  else
 	    break;
 	}
@@ -135,8 +145,11 @@
 
   bytes_stored = read_pos - (ptr + offset);
 
+ unlock_done:
+  funlockfile (stream);
+
  done:
   *lineptr = ptr;
   *linesize = size;
-  return bytes_stored;
+  return bytes_stored ? bytes_stored : -1;
 }

--- a/m4/getndelim2.m4
+++ b/m4/getndelim2.m4
@@ -1,5 +1,5 @@
-# getndelim2.m4 serial 5
-dnl Copyright (C) 2003, 2006 Free Software Foundation, Inc.
+# getndelim2.m4 serial 6
+dnl Copyright (C) 2003, 2006, 2008 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
 dnl with or without modifications, as long as this notice is preserved.
@@ -8,6 +8,8 @@
 [
   AC_LIBOBJ(getndelim2)
   gl_PREREQ_GETNDELIM2
+  AC_CHECK_FUNCS_ONCE([flockfile])
+  AC_CHECK_FUNCS_ONCE([funlockfile])
 ])
 
 # Prerequisites of lib/getndelim2.h and lib/getndelim2.c.

new file mode 100644
--- /dev/null
+++ b/modules/getndelim2-tests
@@ -0,0 +1,11 @@
+Files:
+tests/test-getndelim2.c
+
+Depends-on:
+
+configure.ac:
+
+Makefile.am:
+TESTS += test-getndelim2
+check_PROGRAMS += test-getndelim2
+MOSTLYCLEANFILES += test-getndelim2.txt

new file mode 100644
--- /dev/null
+++ b/tests/test-getndelim2.c
@@ -0,0 +1,162 @@
+/* Test of getndelim2() function.
+   Copyright (C) 2008 Free Software Foundation, Inc.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3, or (at your option)
+   any later version.
+
+   This program 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 General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software Foundation,
+   Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  */
+
+/* Written by Eric Blake <ebb9@byu.net>, 2008.  */
+
+#include <config.h>
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "getndelim2.h"
+
+#define ASSERT(expr) \
+  do									     \
+    {									     \
+      if (!(expr))							     \
+        {								     \
+          fprintf (stderr, "%s:%d: assertion failed\n", __FILE__, __LINE__); \
+          fflush (stderr);						     \
+          abort ();							     \
+        }								     \
+    }									     \
+  while (0)
+
+int
+main (int argc, char **argv)
+{
+  FILE *f;
+  char *line = NULL;
+  size_t len = 0;
+  ssize_t result;
+
+  /* Create test file.  */
+  f = fopen ("test-getndelim2.txt", "wb+");
+  if (!f || fwrite ("a\nbc\nd\0f", 1, 8, f) != 8)
+    {
+      fputs ("Failed to create sample file.\n", stderr);
+      remove ("test-getndelim2.txt");
+      return 1;
+    }
+  rewind (f);
+
+  /* Unlimited lines.  */
+
+  /* Test initial allocation, which must include trailing NUL.  */
+  result = getndelim2 (&line, &len, 0, GETNLINE_NO_LIMIT, '\n', '\n', f);
+  ASSERT (result == 2);
+  ASSERT (strcmp (line, "a\n") == 0);
+  ASSERT (2 < len);
+
+  /* Test growth of buffer, must not leak.  */
+  free (line);
+  line = malloc (1);
+  len = 0;
+  result = getndelim2 (&line, &len, 0, GETNLINE_NO_LIMIT, EOF, '\n', f);
+  ASSERT (result == 3);
+  ASSERT (strcmp (line, "bc\n") == 0);
+  ASSERT (3 < len);
+
+  /* Test embedded NULs and EOF behavior.  */
+  result = getndelim2 (&line, &len, 0, GETNLINE_NO_LIMIT, '\n', EOF, f);
+  ASSERT (result == 3);
+  ASSERT (memcmp (line, "d\0f", 4) == 0);
+  ASSERT (3 < len);
+
+  result = getndelim2 (&line, &len, 0, GETNLINE_NO_LIMIT, '\n', EOF, f);
+  ASSERT (result == -1);
+
+  /* Using offset and nmax.  */
+
+  /* Limit growth to four bytes, including NUL, but parse to next 'd'.  */
+  free (line);
+  rewind (f);
+  line = malloc (8);
+  memset (line, 'e', 8);
+  len = 8;
+  result = getndelim2 (&line, &len, 6, 10, 'd', 'd', f);
+  ASSERT (result == 3);
+  ASSERT (10 == len);
+  ASSERT (strcmp (line, "eeeeeea\nb") == 0);
+
+  /* No change if offset larger than limit.  */
+  result = getndelim2 (&line, &len, len, 1, EOF, EOF, f);
+  ASSERT (result == -1);
+  ASSERT (10 == len);
+  ASSERT (strcmp (line, "eeeeeea\nb") == 0);
+
+  /* Consume to end of file, including embedded NUL.  */
+  result = getndelim2 (&line, &len, 0, GETNLINE_NO_LIMIT, EOF, EOF, f);
+  ASSERT (result == 2);
+  ASSERT (10 == len);
+  ASSERT (memcmp (line, "\0f\0eeea\nb", 10) == 0);
+
+  result = getndelim2 (&line, &len, 0, GETNLINE_NO_LIMIT, '\n', '\r', f);
+  ASSERT (result == -1);
+
+  /* Larger file size.  */
+  rewind (f);
+  {
+    int i;
+    for (i = 0; i < 16; i++)
+      fprintf (f, "%500x%c", i, i % 2 ? '\n' : '\r');
+  }
+  rewind (f);
+  {
+    char buffer[502];
+
+    result = getndelim2 (&line, &len, 0, GETNLINE_NO_LIMIT, '\n', '\r', f);
+    ASSERT (result == 501);
+    ASSERT (501 < len);
+    memset (buffer, ' ', 499);
+    buffer[499] = '0';
+    buffer[500] = '\r';
+    buffer[501] = '\0';
+    ASSERT (strcmp (buffer, line) == 0);
+
+    result = getndelim2 (&line, &len, 0, GETNLINE_NO_LIMIT, '\n', '\r', f);
+    ASSERT (result == 501);
+    ASSERT (501 < len);
+    buffer[499] = '1';
+    buffer[500] = '\n';
+    ASSERT (strcmp (buffer, line) == 0);
+
+    result = getndelim2 (&line, &len, 0, GETNLINE_NO_LIMIT, 'g', 'f', f);
+    ASSERT (result == 501 * 14 - 1);
+    ASSERT (501 * 14 < len);
+    buffer[499] = 'f';
+    buffer[500] = '\0';
+    ASSERT (strcmp (buffer, line + 501 * 13) == 0);
+
+    result = getndelim2 (&line, &len, 501 * 14 - 1, GETNLINE_NO_LIMIT,
+			 EOF, EOF, f);
+    ASSERT (result == 1);
+    buffer[500] = '\n';
+    ASSERT (strcmp (buffer, line + 501 * 13) == 0);
+
+    result = getndelim2 (&line, &len, 501 * 14 - 1, GETNLINE_NO_LIMIT,
+			 EOF, EOF, f);
+    buffer[500] = '\0';
+    ASSERT (strcmp (buffer, line + 501 * 13) == 0);
+    ASSERT (result == -1);
+  }
+
+  fclose (f);
+  remove ("test-getndelim2.txt");
+  return 0;
+}