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new 1dfa0288084 include/fcntl.h: keep open() flags within a 16-bit int
1dfa0288084 is described below
commit 1dfa028808454c8d256678e585af5293200bb2ef
Author: Alan Carvalho de Assis <[email protected]>
AuthorDate: Tue Sep 29 21:21:29 2026 -0300
include/fcntl.h: keep open() flags within a 16-bit int
O_DIRECTORY, O_NOFOLLOW, O_NOATIME, O_CLOEXEC, __O_SYNC, O_PATH and
__O_TMPFILE are defined as shifts by 16 to 22 bits. Where int is 16
bits (AVR, for example), these shifts exceed the width of the type:
GCC evaluates them to 0, and the -Wshift-count-overflow warning is not
shown because include/ is a system include directory. The oflags
argument of open() is an int, so it could not carry those bits anyway.
As a result, on arch with int equal 16-bit opendir() opens directories
without O_DIRECTORY, so opening a mount point such as /proc fails with
ENOENT, and O_CLOEXEC and O_NOFOLLOW have no effect.
When UINT_MAX is 0xffff, use the unused bits 2 to 4 for O_DIRECTORY,
O_CLOEXEC and O_NOFOLLOW, define O_NOATIME and __O_SYNC as 0 (O_SYNC
falls back to O_DSYNC), and leave O_PATH and O_TMPFILE undefined, so
that code which needs them fails to build instead of silently opening
with the wrong flags; nothing in the tree uses them. _O_MAXBIT becomes
15. On bigger systems (32-bit, 64-bit) keep the original bit shift.
Signed-off-by: Alan Carvalho de Assis <[email protected]>
Assisted-by: Claude Opus 5.5 (claude-opus-5-5)
---
include/fcntl.h | 38 +++++++++++++++++++++++++++++---------
1 file changed, 29 insertions(+), 9 deletions(-)
diff --git a/include/fcntl.h b/include/fcntl.h
index 05f2ade7185..8cd50c6eeda 100644
--- a/include/fcntl.h
+++ b/include/fcntl.h
@@ -30,6 +30,7 @@
#include <nuttx/config.h>
#include <sys/types.h>
+#include <limits.h>
#include <stdint.h>
/****************************************************************************
@@ -59,25 +60,44 @@
#define O_ASYNC (1U << 13) /* Enable signal-driven I/O */
#define O_DIRECT (1U << 14) /* Avoid caching, write directly to
hardware */
#define O_LARGEFILE (1U << 15) /* Large File */
-#define O_DIRECTORY (1U << 16) /* Must be a directory */
-#define O_NOFOLLOW (1U << 17) /* Don't follow links */
-#define O_NOATIME (1U << 18) /* Don't update the file last access time
*/
-#define O_CLOEXEC (1U << 19) /* Close on execute */
-#define __O_SYNC (1U << 20) /* Synchronize file (data+metadata) */
-#define O_PATH (1U << 21) /* Obtain a path-only fd (no I/O) */
-#define __O_TMPFILE (1U << 22) /* Create an unnamed temporary file */
+
+#if UINT_MAX > 0xffff
+# define O_DIRECTORY (1U << 16) /* Must be a directory */
+# define O_NOFOLLOW (1U << 17) /* Don't follow links */
+# define O_NOATIME (1U << 18) /* Don't update the file last access time
*/
+# define O_CLOEXEC (1U << 19) /* Close on execute */
+# define __O_SYNC (1U << 20) /* Synchronize file (data+metadata) */
+# define O_PATH (1U << 21) /* Obtain a path-only fd (no I/O) */
+# define __O_TMPFILE (1U << 22) /* Create an unnamed temporary file */
+# define O_TMPFILE (__O_TMPFILE | O_DIRECTORY)
+#else
+/* With a 16-bit int, the oflags argument of open() holds bits 0-15 only.
+ * The flags that the VFS and the C library act on use the free bits 2-4.
+ * O_NOATIME is only a hint and O_SYNC falls back to O_DSYNC; O_PATH and
+ * O_TMPFILE are not available.
+ */
+
+# define O_DIRECTORY (1U << 2) /* Must be a directory */
+# define O_CLOEXEC (1U << 3) /* Close on execute */
+# define O_NOFOLLOW (1U << 4) /* Don't follow links */
+# define O_NOATIME 0 /* Not supported */
+# define __O_SYNC 0 /* Not supported: O_SYNC is O_DSYNC */
+#endif
#define O_NDELAY O_NONBLOCK /* Synonym for O_NONBLOCK */
#define O_SYNC (__O_SYNC | O_DSYNC) /* Synchronize output on
write */
#define O_RSYNC O_SYNC /* Synchronize input on read
*/
-#define O_TMPFILE (__O_TMPFILE | O_DIRECTORY) /* Create a temporary file */
#define O_BINARY 0 /* Open the file in binary
mode */
/* This is the highest bit number used in the open flags bitset. Bits above
* this bit number may be used within NuttX for other, internal purposes.
*/
-#define _O_MAXBIT 22
+#if UINT_MAX > 0xffff
+# define _O_MAXBIT 22
+#else
+# define _O_MAXBIT 15
+#endif
/* Synonyms historically used as F_SETFL flags (BSD). */
