readlinkat: split into its own module

* modules/symlinkat: Split readlinkat...
* modules/readlinkat: ...into separate module.
* m4/symlinkat.m4 (gl_FUNC_SYMLINKAT): Move readlinkat check...
* m4/readlinkat.m4 (gl_FUNC_READLINAT): ...to new file.
* lib/symlinkat.c (readlinkat): Move...
* lib/readlinkat.c: ...into new file.
* modules/symlinkat-tests: Split readlinkat test...
* modules/readlinkat-tests: ...into separate module.
* tests/test-symlinkat.c: Split...
* tests/test-readlinkat.c: ...into new file.
* NEWS: Document the split.
* doc/posix-functions/readlinkat.texi (readlinkat): Likewise.
* lib/unistd.in.h (readlinkat): Likewise.
Suggested by Bruno Haible.

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

14 files changed, 250 insertions, 84 deletions

diff --git a/ChangeLog b/ChangeLog
index 3c7a86eb47..2e71438290 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,21 @@
+2010-08-09  Eric Blake  <eblake@redhat.com>
+
+	readlinkat: split into its own module
+	* modules/symlinkat: Split readlinkat...
+	* modules/readlinkat: ...into separate module.
+	* m4/symlinkat.m4 (gl_FUNC_SYMLINKAT): Move readlinkat check...
+	* m4/readlinkat.m4 (gl_FUNC_READLINAT): ...to new file.
+	* lib/symlinkat.c (readlinkat): Move...
+	* lib/readlinkat.c: ...into new file.
+	* modules/symlinkat-tests: Split readlinkat test...
+	* modules/readlinkat-tests: ...into separate module.
+	* tests/test-symlinkat.c: Split...
+	* tests/test-readlinkat.c: ...into new file.
+	* NEWS: Document the split.
+	* doc/posix-functions/readlinkat.texi (readlinkat): Likewise.
+	* lib/unistd.in.h (readlinkat): Likewise.
+	Suggested by Bruno Haible.
+
 2010-08-08  Bruno Haible  <bruno@clisp.org>
 
 	memxfrm: Speed up.
diff --git a/NEWS b/NEWS
index f8b125a36a..ff3bfb6c2f 100644
--- a/NEWS
+++ b/NEWS
@@ -6,6 +6,9 @@ User visible incompatible changes
 
 Date        Modules         Changes
 
+2010-08-09  symlinkat       This module now only provides symlinkat; use the
+                            new module 'readlinkat' if needed.
+
 2010-07-31  ansi-c++-opt    If Autoconf >= 2.66 is used, the 'configure'
                             option is now called --disable-c++ rather than
                             --disable-cxx.
diff --git a/doc/posix-functions/readlinkat.texi b/doc/posix-functions/readlinkat.texi
index 2cbaf624ad..4cef743681 100644
--- a/doc/posix-functions/readlinkat.texi
+++ b/doc/posix-functions/readlinkat.texi
@@ -4,7 +4,7 @@
 
 POSIX specification: @url{http://www.opengroup.org/onlinepubs/9699919799/functions/readlinkat.html}
 
-Gnulib module: symlinkat
+Gnulib module: readlinkat
 
 Portability problems fixed by Gnulib:
 @itemize
diff --git a/lib/readlinkat.c b/lib/readlinkat.c
new file mode 100644
index 0000000000..de80ba3071
--- /dev/null
+++ b/lib/readlinkat.c
@@ -0,0 +1,47 @@
+/* Read a symlink relative to an open directory.
+   Copyright (C) 2009-2010 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 of the License, 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, see <http://www.gnu.org/licenses/>.  */
+
+/* written by Eric Blake */
+
+#include <config.h>
+
+#include <unistd.h>
+
+/* Gnulib provides a readlink stub for mingw; use it for distinction
+   between EINVAL and ENOENT, rather than always failing with ENOSYS.  */
+
+/* POSIX 2008 says that unlike readlink, readlinkat returns 0 for
+   success instead of the buffer length.  But this would render
+   readlinkat worthless since readlink does not guarantee a
+   NUL-terminated buffer.  Assume this was a bug in POSIX.  */
+
+/* Read the contents of symlink FILE into buffer BUF of size LEN, in the
+   directory open on descriptor FD.  If possible, do it without changing
+   the working directory.  Otherwise, resort to using save_cwd/fchdir,
+   then readlink/restore_cwd.  If either the save_cwd or the restore_cwd
+   fails, then give a diagnostic and exit nonzero.  */
+
+#define AT_FUNC_NAME readlinkat
+#define AT_FUNC_F1 readlink
+#define AT_FUNC_POST_FILE_PARAM_DECLS , char *buf, size_t len
+#define AT_FUNC_POST_FILE_ARGS        , buf, len
+#define AT_FUNC_RESULT ssize_t
+#include "at-func.c"
+#undef AT_FUNC_NAME
+#undef AT_FUNC_F1
+#undef AT_FUNC_POST_FILE_PARAM_DECLS
+#undef AT_FUNC_POST_FILE_ARGS
+#undef AT_FUNC_RESULT
diff --git a/lib/symlinkat.c b/lib/symlinkat.c
index c01b3228d9..57cd5c5f86 100644
--- a/lib/symlinkat.c
+++ b/lib/symlinkat.c
@@ -74,29 +74,3 @@ symlinkat (char const *contents, int fd, char const *file)
 }
 
 #endif /* HAVE_SYMLINK */
-
-/* Gnulib provides a readlink stub for mingw; use it for distinction
-   between EINVAL and ENOENT, rather than always failing with ENOSYS.  */
-
-/* POSIX 2008 says that unlike readlink, readlinkat returns 0 for
-   success instead of the buffer length.  But this would render
-   readlinkat worthless since readlink does not guarantee a
-   NUL-terminated buffer.  Assume this was a bug in POSIX.  */
-
-/* Read the contents of symlink FILE into buffer BUF of size LEN, in the
-   directory open on descriptor FD.  If possible, do it without changing
-   the working directory.  Otherwise, resort to using save_cwd/fchdir,
-   then readlink/restore_cwd.  If either the save_cwd or the restore_cwd
-   fails, then give a diagnostic and exit nonzero.  */
-
-#define AT_FUNC_NAME readlinkat
-#define AT_FUNC_F1 readlink
-#define AT_FUNC_POST_FILE_PARAM_DECLS , char *buf, size_t len
-#define AT_FUNC_POST_FILE_ARGS        , buf, len
-#define AT_FUNC_RESULT ssize_t
-#include "at-func.c"
-#undef AT_FUNC_NAME
-#undef AT_FUNC_F1
-#undef AT_FUNC_POST_FILE_PARAM_DECLS
-#undef AT_FUNC_POST_FILE_ARGS
-#undef AT_FUNC_RESULT
diff --git a/lib/unistd.in.h b/lib/unistd.in.h
index 49f6badf41..4c9a4a8f9d 100644
--- a/lib/unistd.in.h
+++ b/lib/unistd.in.h
@@ -1097,7 +1097,7 @@ _GL_CXXALIASWARN (readlinkat);
 # undef readlinkat
 # if HAVE_RAW_DECL_READLINKAT
 _GL_WARN_ON_USE (readlinkat, "readlinkat is not portable - "
-                 "use gnulib module symlinkat for portability");
+                 "use gnulib module readlinkat for portability");
 # endif
 #endif
 
diff --git a/m4/readlinkat.m4 b/m4/readlinkat.m4
new file mode 100644
index 0000000000..a3897498ae
--- /dev/null
+++ b/m4/readlinkat.m4
@@ -0,0 +1,21 @@
+# serial 1
+# See if we need to provide readlinkat replacement.
+
+dnl Copyright (C) 2009-2010 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.
+
+# Written by Eric Blake.
+
+AC_DEFUN([gl_FUNC_READLINKAT],
+[
+  AC_REQUIRE([gl_FUNC_OPENAT])
+  AC_REQUIRE([gl_UNISTD_H_DEFAULTS])
+  AC_REQUIRE([gl_USE_SYSTEM_EXTENSIONS])
+  AC_CHECK_FUNCS_ONCE([readlinkat])
+  if test $ac_cv_func_readlinkat = no; then
+    HAVE_READLINKAT=0
+    AC_LIBOBJ([readlinkat])
+  fi
+])
diff --git a/m4/symlinkat.m4 b/m4/symlinkat.m4
index 8466944a52..ed8bb87cd8 100644
--- a/m4/symlinkat.m4
+++ b/m4/symlinkat.m4
@@ -1,5 +1,5 @@
-# serial 3
-# See if we need to provide symlinkat/readlinkat replacement.
+# serial 4
+# See if we need to provide symlinkat replacement.
 
 dnl Copyright (C) 2009-2010 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
@@ -13,11 +13,9 @@ AC_DEFUN([gl_FUNC_SYMLINKAT],
   AC_REQUIRE([gl_FUNC_OPENAT])
   AC_REQUIRE([gl_UNISTD_H_DEFAULTS])
   AC_REQUIRE([gl_USE_SYSTEM_EXTENSIONS])
-  AC_CHECK_FUNCS_ONCE([symlinkat readlinkat])
+  AC_CHECK_FUNCS_ONCE([symlinkat])
   if test $ac_cv_func_symlinkat = no; then
-    # No known system has readlinkat but not symlinkat
     HAVE_SYMLINKAT=0
-    HAVE_READLINKAT=0
     AC_LIBOBJ([symlinkat])
   fi
 ])
diff --git a/modules/readlinkat b/modules/readlinkat
new file mode 100644
index 0000000000..593f2c2573
--- /dev/null
+++ b/modules/readlinkat
@@ -0,0 +1,29 @@
+Description:
+readlinkat(): read symlinks relative to a directory
+
+Files:
+lib/readlinkat.c
+m4/readlinkat.m4
+
+Depends-on:
+extensions
+fcntl-h
+openat
+readlink
+unistd
+
+configure.ac:
+gl_FUNC_READLINKAT
+gl_UNISTD_MODULE_INDICATOR([readlinkat])
+
+Makefile.am:
+
+Include:
+<fcntl.h>
+<unistd.h>
+
+License:
+GPL
+
+Maintainer:
+Jim Meyering, Eric Blake
diff --git a/modules/readlinkat-tests b/modules/readlinkat-tests
new file mode 100644
index 0000000000..de23df8dde
--- /dev/null
+++ b/modules/readlinkat-tests
@@ -0,0 +1,16 @@
+Files:
+tests/test-readlink.h
+tests/test-readlinkat.c
+tests/signature.h
+tests/macros.h
+
+Depends-on:
+ignore-value
+symlinkat
+
+configure.ac:
+
+Makefile.am:
+TESTS += test-readlinkat
+check_PROGRAMS += test-readlinkat
+test_readlinkat_LDADD = $(LDADD) @LIBINTL@
diff --git a/modules/symlinkat b/modules/symlinkat
index 1a065fdfe2..16646be699 100644
--- a/modules/symlinkat
+++ b/modules/symlinkat
@@ -1,5 +1,5 @@
 Description:
-symlinkat() and readlinkat(): manage symlinks relative to a directory
+symlinkat(): create symlinks relative to a directory
 
 Files:
 lib/symlinkat.c
@@ -9,14 +9,12 @@ Depends-on:
 extensions
 fcntl-h
 openat
-readlink
 symlink
 unistd
 
 configure.ac:
 gl_FUNC_SYMLINKAT
 gl_UNISTD_MODULE_INDICATOR([symlinkat])
-gl_UNISTD_MODULE_INDICATOR([readlinkat])
 
 Makefile.am:
 
diff --git a/modules/symlinkat-tests b/modules/symlinkat-tests
index c1678c0218..90331494a4 100644
--- a/modules/symlinkat-tests
+++ b/modules/symlinkat-tests
@@ -1,5 +1,4 @@
 Files:
-tests/test-readlink.h
 tests/test-symlink.h
 tests/test-symlinkat.c
 tests/signature.h
diff --git a/tests/test-readlinkat.c b/tests/test-readlinkat.c
new file mode 100644
index 0000000000..5a5d806816
--- /dev/null
+++ b/tests/test-readlinkat.c
@@ -0,0 +1,108 @@
+/* Tests of readlinkat.
+   Copyright (C) 2009, 2010 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 of the License, 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, see <http://www.gnu.org/licenses/>.  */
+
+/* Written by Eric Blake <ebb9@byu.net>, 2009.  */
+
+#include <config.h>
+
+#include <unistd.h>
+
+#include "signature.h"
+SIGNATURE_CHECK (readlinkat, ssize_t, (int, char const *, char *, size_t));
+
+#include <fcntl.h>
+#include <errno.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/stat.h>
+
+#include "ignore-value.h"
+#include "macros.h"
+
+#ifndef HAVE_SYMLINK
+# define HAVE_SYMLINK 0
+#endif
+
+#define BASE "test-readlinkat.t"
+
+#include "test-readlink.h"
+
+static int dfd = AT_FDCWD;
+
+static ssize_t
+do_readlink (char const *name, char *buf, size_t len)
+{
+  return readlinkat (dfd, name, buf, len);
+}
+
+int
+main (void)
+{
+  char buf[80];
+  int result;
+
+  /* Remove any leftovers from a previous partial run.  */
+  ignore_value (system ("rm -rf " BASE "*"));
+
+  /* Perform same checks as counterpart functions.  */
+  result = test_readlink (do_readlink, false);
+  dfd = openat (AT_FDCWD, ".", O_RDONLY);
+  ASSERT (0 <= dfd);
+  ASSERT (test_readlink (do_readlink, false) == result);
+
+  /* Now perform some cross-directory checks.  Skip everything else on
+     mingw.  */
+  if (HAVE_SYMLINK)
+    {
+      const char *contents = "don't matter!";
+      ssize_t exp = strlen (contents);
+
+      /* Create link while cwd is '.', then read it in '..'.  */
+      ASSERT (symlinkat (contents, AT_FDCWD, BASE "link") == 0);
+      errno = 0;
+      ASSERT (symlinkat (contents, dfd, BASE "link") == -1);
+      ASSERT (errno == EEXIST);
+      ASSERT (chdir ("..") == 0);
+      errno = 0;
+      ASSERT (readlinkat (AT_FDCWD, BASE "link", buf, sizeof buf) == -1);
+      ASSERT (errno == ENOENT);
+      ASSERT (readlinkat (dfd, BASE "link", buf, sizeof buf) == exp);
+      ASSERT (strncmp (contents, buf, exp) == 0);
+      ASSERT (unlinkat (dfd, BASE "link", 0) == 0);
+
+      /* Create link while cwd is '..', then read it in '.'.  */
+      ASSERT (symlinkat (contents, dfd, BASE "link") == 0);
+      ASSERT (fchdir (dfd) == 0);
+      errno = 0;
+      ASSERT (symlinkat (contents, AT_FDCWD, BASE "link") == -1);
+      ASSERT (errno == EEXIST);
+      buf[0] = '\0';
+      ASSERT (readlinkat (AT_FDCWD, BASE "link", buf, sizeof buf) == exp);
+      ASSERT (strncmp (contents, buf, exp) == 0);
+      buf[0] = '\0';
+      ASSERT (readlinkat (dfd, BASE "link", buf, sizeof buf) == exp);
+      ASSERT (strncmp (contents, buf, exp) == 0);
+      ASSERT (unlink (BASE "link") == 0);
+    }
+
+  ASSERT (close (dfd) == 0);
+  if (result == 77)
+    fputs ("skipping test: symlinks not supported on this file system\n",
+           stderr);
+  return result;
+}
diff --git a/tests/test-symlinkat.c b/tests/test-symlinkat.c
index c3dec293db..8cdc86d79d 100644
--- a/tests/test-symlinkat.c
+++ b/tests/test-symlinkat.c
@@ -1,4 +1,4 @@
-/* Tests of symlinkat and readlinkat.
+/* Tests of symlinkat.
    Copyright (C) 2009, 2010 Free Software Foundation, Inc.
 
    This program is free software: you can redistribute it and/or modify
@@ -22,7 +22,6 @@
 
 #include "signature.h"
 SIGNATURE_CHECK (symlinkat, int, (char const *, int, char const *));
-SIGNATURE_CHECK (readlinkat, ssize_t, (int, char const *, char *, size_t));
 
 #include <fcntl.h>
 #include <errno.h>
@@ -41,7 +40,6 @@ SIGNATURE_CHECK (readlinkat, ssize_t, (int, char const *, char *, size_t));
 
 #define BASE "test-symlinkat.t"
 
-#include "test-readlink.h"
 #include "test-symlink.h"
 
 static int dfd = AT_FDCWD;
@@ -52,12 +50,6 @@ do_symlink (char const *contents, char const *name)
   return symlinkat (contents, dfd, name);
 }
 
-static ssize_t
-do_readlink (char const *name, char *buf, size_t len)
-{
-  return readlinkat (dfd, name, buf, len);
-}
-
 int
 main (void)
 {
@@ -68,48 +60,11 @@ main (void)
   ignore_value (system ("rm -rf " BASE "*"));
 
   /* Perform same checks as counterpart functions.  */
-  result = test_readlink (do_readlink, false);
-  ASSERT (test_symlink (do_symlink, false) == result);
+  result = test_symlink (do_symlink, false);
   dfd = openat (AT_FDCWD, ".", O_RDONLY);
   ASSERT (0 <= dfd);
-  ASSERT (test_readlink (do_readlink, false) == result);
   ASSERT (test_symlink (do_symlink, false) == result);
 
-  /* Now perform some cross-directory checks.  Skip everything else on
-     mingw.  */
-  if (HAVE_SYMLINK)
-    {
-      const char *contents = "don't matter!";
-      ssize_t exp = strlen (contents);
-
-      /* Create link while cwd is '.', then read it in '..'.  */
-      ASSERT (symlinkat (contents, AT_FDCWD, BASE "link") == 0);
-      errno = 0;
-      ASSERT (symlinkat (contents, dfd, BASE "link") == -1);
-      ASSERT (errno == EEXIST);
-      ASSERT (chdir ("..") == 0);
-      errno = 0;
-      ASSERT (readlinkat (AT_FDCWD, BASE "link", buf, sizeof buf) == -1);
-      ASSERT (errno == ENOENT);
-      ASSERT (readlinkat (dfd, BASE "link", buf, sizeof buf) == exp);
-      ASSERT (strncmp (contents, buf, exp) == 0);
-      ASSERT (unlinkat (dfd, BASE "link", 0) == 0);
-
-      /* Create link while cwd is '..', then read it in '.'.  */
-      ASSERT (symlinkat (contents, dfd, BASE "link") == 0);
-      ASSERT (fchdir (dfd) == 0);
-      errno = 0;
-      ASSERT (symlinkat (contents, AT_FDCWD, BASE "link") == -1);
-      ASSERT (errno == EEXIST);
-      buf[0] = '\0';
-      ASSERT (readlinkat (AT_FDCWD, BASE "link", buf, sizeof buf) == exp);
-      ASSERT (strncmp (contents, buf, exp) == 0);
-      buf[0] = '\0';
-      ASSERT (readlinkat (dfd, BASE "link", buf, sizeof buf) == exp);
-      ASSERT (strncmp (contents, buf, exp) == 0);
-      ASSERT (unlink (BASE "link") == 0);
-    }
-
   ASSERT (close (dfd) == 0);
   if (result == 77)
     fputs ("skipping test: symlinks not supported on this file system\n",