--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,12 @@
+2011-01-02  Bruno Haible  <bruno@clisp.org>
+
+	pwrite: Fix test whether it works and make it work on HP-UX 11.11.
+	* m4/pwrite.m4 (gl_FUNC_PWRITE): Use AC_LANG_PROGRAM, not
+	AC_LANG_SOURCE. Extend the test program to catch another HP-UX 11.11
+	bug.
+	* lib/pwrite.c: Undo 2010-12-31 patch.
+	* doc/posix-functions/pwrite.texi: Document another HP-UX 11.11 bug.
+
 2011-01-02  Bruno Haible  <bruno@clisp.org>
 
 	pread: Fix test whether it works.

--- a/doc/posix-functions/pwrite.texi
+++ b/doc/posix-functions/pwrite.texi
@@ -15,6 +15,10 @@
 This function does not fail when an invalid (negative) offset is passed when
 large file support is enabled on some platforms:
 HP-UX 11.11.
+@item
+This function uses an arbitrary offset instead of the @code{off_t} argument
+when large file support is enabled on some platforms:
+HP-UX 11.11.
 @end itemize
 
 Portability problems not fixed by Gnulib:

--- a/lib/pwrite.c
+++ b/lib/pwrite.c
@@ -24,25 +24,9 @@
 
 #include <errno.h>
 
-#if HAVE_PWRITE
-
-ssize_t
-pwrite (int fd, const void *buf, size_t nbyte, off_t offset)
-# undef pwrite
-{
-  if (offset < 0)
-    {
-      errno = EINVAL;
-      return -1;
-    }
-  return pwrite (fd, buf, nbyte, offset);
-}
-
-#else
-
-# define __libc_lseek(f,o,w) lseek (f, o, w)
-# define __set_errno(Val) errno = (Val)
-# define __libc_write(f,b,n) write (f, b, n)
+#define __libc_lseek(f,o,w) lseek (f, o, w)
+#define __set_errno(Val) errno = (Val)
+#define __libc_write(f,b,n) write (f, b, n)
 
 /* Note: This implementation of pwrite is not multithread-safe.  */
 
@@ -78,5 +62,3 @@
 
   return result;
 }
-
-#endif

--- a/m4/pwrite.m4
+++ b/m4/pwrite.m4
@@ -1,4 +1,4 @@
-# pwrite.m4 serial 2
+# pwrite.m4 serial 3
 dnl Copyright (C) 2010-2011 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -15,7 +15,8 @@
   AC_CHECK_FUNCS_ONCE([pwrite])
   if test $ac_cv_func_pwrite = yes; then
     dnl On HP-UX 11.11 with _FILE_OFFSET_BITS=64, pwrite() on a file does not
-    dnl fail when an invalid (negative) offset is passed.
+    dnl fail when an invalid (negative) offset is passed and uses an arbitrary
+    dnl offset instead of the argument.
     AC_CACHE_CHECK([whether pwrite works],
       [gl_cv_func_pwrite_works],
       [
@@ -32,7 +33,7 @@
         CPPFLAGS="$CPPFLAGS -D_FILE_OFFSET_BITS=64"
         rm -f conftest.out
         AC_RUN_IFELSE(
-          [AC_LANG_SOURCE([[
+          [AC_LANG_PROGRAM([[
 #include <sys/types.h>
 #include <unistd.h>
 #include <fcntl.h>
@@ -47,6 +48,43 @@
     if (pwrite (fd, "b", 1, (off_t) -1) >= 0)
       return 2;
   }
+  /* This test fails on HP-UX 11.00..11.11.  */
+  {
+    int fd;
+    char buf[] = "01";
+
+    fd = open ("conftest.out", O_WRONLY | O_CREAT | O_TRUNC, 0600);
+    if (fd < 0)
+      return 3;
+    if (write (fd, buf, 2) < 2)
+      return 4;
+    if (close (fd) < 0)
+      return 5;
+
+    fd = open ("conftest.out", O_WRONLY, 0600);
+    if (fd < 0)
+      return 6;
+    if (pwrite (fd, "W", 1, (off_t) 0) != 1)
+      return 7;
+    if (close (fd) < 0)
+      return 8;
+
+    fd = open ("conftest.out", O_RDONLY);
+    if (fd < 0)
+      return 9;
+    if (read (fd, buf, 2) < 2)
+      return 10;
+    if (close (fd) < 0)
+      return 11;
+    if (buf[0] != 'W')
+      return 12;
+    if (buf[1] != '1')
+      return 13;
+  }
+  return 0;
+}
+
+
   return 0;
 }]])],
           [gl_cv_func_pwrite_works=yes],