casaroli opened a new pull request, #20752:
URL: https://github.com/apache/nuttx/pull/20752
## Summary
POSIX says that an empty path names no file, so the call fails with
`ENOENT`. `access("")`, `stat("")`, `lstat("")` and `open("")` already do this.
The `*at()` functions did not: `lib_getfullpath()` turned `""` into the
directory itself (`$PWD/` or the path of `dirfd`). So `faccessat(AT_FDCWD, "",
X_OK)` returned 0, `fstatat(AT_FDCWD, "", 0)` returned the current directory,
and `openat(AT_FDCWD, "")` failed with `ENXIO`.
- The second commit makes `lib_getfullpath()` return `-ENOENT` for `""`.
This fixes all `*at()` functions at once: `faccessat`, `fstatat`, `openat`,
`mkdirat`, `unlinkat`, `fchownat`, `linkat`, `symlinkat`, `readlinkat`,
`utimensat`, `renameat`, `mkfifoat` and `mknodat`.
- `fstatat(fd, "", AT_EMPTY_PATH)` worked only because of that bug. The
first commit makes `fstatat()` handle `AT_EMPTY_PATH` itself (`fstat(dirfd)`,
or `"."` for `AT_FDCWD`), so it keeps working.
## Impact
The `*at()` functions now fail with `ENOENT` for an empty path, as POSIX
requires. `fstatat()` with `AT_EMPTY_PATH` does not change.
## Testing
A test program on `qemu-armv8a:knsh` (QEMU 11 with HVF on an Apple M4):
| Check | master | this PR |
|---|---|---|
| `access("")`, `stat("")`, `lstat("")`, `open("")` | `ENOENT` | `ENOENT` |
| `faccessat(AT_FDCWD, "")` | 0 | `ENOENT` |
| `fstatat(AT_FDCWD, "", 0)` | 0 | `ENOENT` |
| `fstatat(dirfd, "", 0)` | 0 | `ENOENT` |
| `openat(AT_FDCWD, "")` | `ENXIO` | `ENOENT` |
| `fstatat()` with `AT_EMPTY_PATH` (`AT_FDCWD`, a directory fd, a file fd) |
ok | ok |
`ostest` on `qemu-armv8a:knsh` and `qemu-armv8a:nsh` ends with `ostest_main:
Exiting with status 0`. `tools/checkpatch.sh -c -u -m -g` passes.
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