[PATCH] fcntl-h: default O_SEARCH, O_EXEC to O_PATH if available

[Paul Eggert]

Linux kernel 2.6.39 introduced O_PATH (see
<http://lwn.net/Articles/433854/>) and this is a better fallback
for O_SEARCH and O_EXEC than O_RDONLY, if O_PATH is available.
* doc/posix-headers/fcntl.texi (fcntl.h): Document this.
* lib/fcntl.in.h (O_EXEC, O_SEARCH) [O_PATH]: Default to O_PATH.
* lib/fcntl.in.h (O_ACCMODE):
* tests/test-fcntl-h.c (main):
Do not reject O_ACCMODE merely because it has more than the
minimal number of bits, as POSIX allows extensions here.
---
 ChangeLog                    | 13 +++++++++++++
 doc/posix-headers/fcntl.texi |  4 +++-
 lib/fcntl.in.h               | 14 +++++++++++---
 tests/test-fcntl-h.c         |  2 +-
 4 files changed, 28 insertions(+), 5 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 2173fb2..3576e7a 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,16 @@
+2012-11-05  Paul Eggert  <address@hidden>
+
+       fcntl-h: default O_SEARCH, O_EXEC to O_PATH if available
+       Linux kernel 2.6.39 introduced O_PATH (see
+       <http://lwn.net/Articles/433854/>) and this is a better fallback
+       for O_SEARCH and O_EXEC than O_RDONLY, if O_PATH is available.
+       * doc/posix-headers/fcntl.texi (fcntl.h): Document this.
+       * lib/fcntl.in.h (O_EXEC, O_SEARCH) [O_PATH]: Default to O_PATH.
+       * lib/fcntl.in.h (O_ACCMODE):
+       * tests/test-fcntl-h.c (main):
+       Do not reject O_ACCMODE merely because it has more than the
+       minimal number of bits, as POSIX allows extensions here.
+
 2012-11-04  Andrew Warshall  <address@hidden>  (tiny change)
 
        mountlist: do not classify a bind-mounted dir entry as "dummy"
diff --git a/doc/posix-headers/fcntl.texi b/doc/posix-headers/fcntl.texi
index eaa885d..4a75a54 100644
--- a/doc/posix-headers/fcntl.texi
+++ b/doc/posix-headers/fcntl.texi
@@ -28,7 +28,9 @@ non-zero value; otherwise, the gnulib replacement is 0.
 
 @item
 @samp{O_EXEC} and @samp{O_SEARCH} are not defined on some platforms.
-Gnulib defines these macros to @samp{O_RDONLY}, which is typically 0.
+On platforms such as GNU/Linux 2.6.39 and later that have @samp{O_PATH},
+Gnulib defines these macros to @samp{O_PATH}.
+On other platforms, it defines them to @samp{O_RDONLY}, which is typically 0.
 
 @item
 @samp{O_ACCMODE} is not defined on some platforms:
diff --git a/lib/fcntl.in.h b/lib/fcntl.in.h
index 5fdac23..fb402ee 100644
--- a/lib/fcntl.in.h
+++ b/lib/fcntl.in.h
@@ -213,7 +213,11 @@ _GL_WARN_ON_USE (openat, "openat is not portable - "
 #endif
 
 #ifndef O_EXEC
-# define O_EXEC O_RDONLY /* This is often close enough in older systems.  */
+# ifdef O_PATH
+#  define O_EXEC O_PATH
+# else
+#  define O_EXEC O_RDONLY /* This is often close enough in older systems.  */
+# endif
 #endif
 
 #ifndef O_IGNORE_CTTY
@@ -270,7 +274,11 @@ _GL_WARN_ON_USE (openat, "openat is not portable - "
 #endif
 
 #ifndef O_SEARCH
-# define O_SEARCH O_RDONLY /* This is often close enough in older systems.  */
+# ifdef O_PATH
+#  define O_SEARCH O_PATH
+# else
+#  define O_SEARCH O_RDONLY /* This is often close enough in older systems.  */
+# endif
 #endif
 
 #ifndef O_SYNC
@@ -281,7 +289,7 @@ _GL_WARN_ON_USE (openat, "openat is not portable - "
 # define O_TTY_INIT 0
 #endif
 
-#if O_ACCMODE != (O_RDONLY | O_WRONLY | O_RDWR | O_EXEC | O_SEARCH)
+#if ~O_ACCMODE & (O_RDONLY | O_WRONLY | O_RDWR | O_EXEC | O_SEARCH)
 # undef O_ACCMODE
 # define O_ACCMODE (O_RDONLY | O_WRONLY | O_RDWR | O_EXEC | O_SEARCH)
 #endif
diff --git a/tests/test-fcntl-h.c b/tests/test-fcntl-h.c
index 9515f82..a6c9621 100644
--- a/tests/test-fcntl-h.c
+++ b/tests/test-fcntl-h.c
@@ -61,7 +61,7 @@ main (void)
 #if O_SEARCH && O_EXEC != O_SEARCH && O_SEARCH != O_RDONLY
     case O_SEARCH:
 #endif
-      i = O_ACCMODE == (O_RDONLY | O_WRONLY | O_RDWR | O_EXEC | O_SEARCH);
+      i = ! (~O_ACCMODE & (O_RDONLY | O_WRONLY | O_RDWR | O_EXEC | O_SEARCH));
       break;
 
       /* Everyone should have these */
-- 
1.7.11.7