fclose: add some tests

POSIX requires that fclose() on seekable input streams rewind back
to the next byte not actually given to the application.  Glibc fails
this test.  See:
http://sourceware.org/bugzilla/show_bug.cgi?id=3746
http://sourceware.org/bugzilla/show_bug.cgi?id=12724

Likewise for FreeBSD.

Cygwin 1.7.9 and Solaris 10 pass, however.

* modules/fclose-tests: New test module.
* tests/test-fclose.c: New file.

Signed-off-by: Eric Blake <eblake@redhat.com>

ChangeLog

@@ -1,5 +1,10 @@
 2011-05-02  Eric Blake  <eblake@redhat.com>
 
+	fclose: add some tests
+	* modules/fclose-tests: New test module.
+	* tests/test-fclose.c: New file.
+	* doc/posix-functions/fclose.texi (fclose): Document the bug.
+
 	fclose: reduced dependencies
 	* modules/fclose (Depends-on): Switch from fflush/fseeko to
 	simpler lseek.

doc/posix-functions/fclose.texi

@@ -17,6 +17,10 @@ followed by @code{fdopen} do not return streams that can be closed by
 Portability problems not fixed by Gnulib:
 @itemize
 @item
+On some platforms, this function fails to set the file position of a
+seekable input stream to the byte after the last one actually read:
+glibc 2.13, FreeBSD.
+@item
 On Windows platforms (excluding Cygwin), this function does not set @code{errno}
 upon failure.
 @end itemize

modules/fclose-tests

@@ -0,0 +1,10 @@
+Files:
+tests/test-fclose.c
+
+Depends-on:
+
+configure.ac:
+
+Makefile.am:
+TESTS += test-fclose
+check_PROGRAMS += test-fclose

tests/test-fclose.c

@@ -0,0 +1,90 @@
+/* Test of fclose module.
+   Copyright (C) 2011 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.  */
+
+#include <config.h>
+
+#include <stdio.h>
+
+#include "signature.h"
+SIGNATURE_CHECK (fclose, int, (FILE *));
+
+#include <errno.h>
+#include <fcntl.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#include "macros.h"
+
+#define BASE "test-fclose.t"
+
+int
+main (int argc, char **argv)
+{
+  const char buf[] = "hello world";
+  int fd;
+  int fd2;
+  FILE *f;
+
+  /* Prepare a seekable file.  */
+  fd = open (BASE, O_RDWR | O_CREAT | O_TRUNC, 0600);
+  ASSERT (0 <= fd);
+  ASSERT (write (fd, buf, sizeof buf) == sizeof buf);
+  ASSERT (lseek (fd, 1, SEEK_SET) == 1);
+
+  /* Create an output stream visiting the file; when it is closed, all
+     other file descriptors visiting the file must see the new file
+     position.  */
+  fd2 = dup (fd);
+  ASSERT (0 <= fd2);
+  f = fdopen (fd2, "w");
+  ASSERT (f);
+  ASSERT (fputc (buf[1], f) == buf[1]);
+  ASSERT (fclose (f) == 0);
+  errno = 0;
+  ASSERT (lseek (fd2, 0, SEEK_CUR) == -1);
+  ASSERT (errno == EBADF);
+  ASSERT (lseek (fd, 0, SEEK_CUR) == 2);
+
+  /* Likewise for an input stream.  */
+  fd2 = dup (fd);
+  ASSERT (0 <= fd2);
+  f = fdopen (fd2, "r");
+  ASSERT (f);
+  ASSERT (fgetc (f) == buf[2]);
+  ASSERT (fclose (f) == 0);
+  errno = 0;
+  ASSERT (lseek (fd2, 0, SEEK_CUR) == -1);
+  ASSERT (errno == EBADF);
+  ASSERT (lseek (fd, 0, SEEK_CUR) == 3);
+
+  /* Test that fclose() sets errno if someone else closes the stream
+     fd behind the back of stdio.  */
+  f = fdopen (fd, "w+");
+  ASSERT (f);
+  ASSERT (close (fd) == 0);
+  errno = 0;
+  ASSERT (fclose (f) == EOF);
+  ASSERT (errno == EBADF);
+
+  /* Clean up.  */
+  ASSERT (remove (BASE) == 0);
+
+  return 0;
+}