Merge #1473 #1474 #1476

1473: sys/stat: add a safe wrapper for mknodat(2) r=asomers a=lucab

This introduces a new `mknodat` helper.

Ref: https://pubs.opengroup.org/onlinepubs/9699919799/functions/mknod.html

1474: Mark most C-derived enums as non_exhaustive r=asomers a=asomers

Since libc may add new variants at any time, Nix's consumers should not
use exhaustive match patterns.

Fixes #1182

1476: Constify many functions r=asomers a=asomers

Constify most functions that can be constified.  The exceptions are
mostly accessors for structs that have no const constructor.

Co-authored-by: Luca BRUNO <luca.bruno@coreos.com>
Co-authored-by: Alan Somers <asomers@gmail.com>

CHANGELOG.md

@@ -16,6 +16,8 @@ This project adheres to [Semantic Versioning](https://semver.org/).
   (#[1471](https://github.com/nix-rust/nix/pull/1471))
 - Added `pthread_kill`.
   (#[1472](https://github.com/nix-rust/nix/pull/1472))
+- Added `mknodat`.
+  (#[1473](https://github.com/nix-rust/nix/pull/1473))
 
 ### Changed
 
@@ -30,6 +32,13 @@ This project adheres to [Semantic Versioning](https://semver.org/).
   builds.
   (#[1481](https://github.com/nix-rust/nix/pull/1481))
 
+- Most enums that come from C, for example `Errno`, are now marked as
+  `#[non_exhaustive]`.
+  (#[1474](https://github.com/nix-rust/nix/pull/1474))
+
+- Many more functions, mostly contructors, are now `const`.
+  (#[1476](https://github.com/nix-rust/nix/pull/1476))
+
 ### Fixed
 
 - Added more errno definitions for better backwards compatibility with

src/errno.rs

@@ -63,7 +63,7 @@ impl Errno {
         since = "0.22.0",
         note = "It's a no-op now; just delete it."
     )]
-    pub fn as_errno(self) -> Option<Self> {
+    pub const fn as_errno(self) -> Option<Self> {
         Some(self)
     }
 
@@ -81,7 +81,7 @@ impl Errno {
         since = "0.22.0",
         note = "Use Errno::EINVAL instead"
     )]
-    pub fn invalid_argument() -> Error {
+    pub const fn invalid_argument() -> Error {
         Errno::EINVAL
     }
 
@@ -122,7 +122,7 @@ impl Errno {
     )]
     #[allow(non_snake_case)]
     #[inline]
-    pub fn Sys(errno: Errno) -> Error {
+    pub const fn Sys(errno: Errno) -> Error {
         errno
     }
 }
@@ -768,6 +768,7 @@ fn desc(errno: Errno) -> &'static str {
 mod consts {
     #[derive(Clone, Copy, Debug, Eq, PartialEq)]
     #[repr(i32)]
+    #[non_exhaustive]
     pub enum Errno {
         UnknownErrno    = 0,
         EPERM           = libc::EPERM,
@@ -1073,6 +1074,7 @@ mod consts {
 mod consts {
     #[derive(Clone, Copy, Debug, Eq, PartialEq)]
     #[repr(i32)]
+    #[non_exhaustive]
     pub enum Errno {
         UnknownErrno    = 0,
         EPERM           = libc::EPERM,
@@ -1324,6 +1326,7 @@ mod consts {
 mod consts {
     #[derive(Clone, Copy, Debug, Eq, PartialEq)]
     #[repr(i32)]
+    #[non_exhaustive]
     pub enum Errno {
         UnknownErrno    = 0,
         EPERM           = libc::EPERM,
@@ -1562,6 +1565,7 @@ mod consts {
 mod consts {
     #[derive(Clone, Copy, Debug, Eq, PartialEq)]
     #[repr(i32)]
+    #[non_exhaustive]
     pub enum Errno {
         UnknownErrno    = 0,
         EPERM           = libc::EPERM,
@@ -1796,6 +1800,7 @@ mod consts {
 mod consts {
     #[derive(Clone, Copy, Debug, Eq, PartialEq)]
     #[repr(i32)]
+    #[non_exhaustive]
     pub enum Errno {
         UnknownErrno    = 0,
         EPERM           = libc::EPERM,
@@ -2019,6 +2024,7 @@ mod consts {
 mod consts {
     #[derive(Clone, Copy, Debug, Eq, PartialEq)]
     #[repr(i32)]
+    #[non_exhaustive]
     pub enum Errno {
         UnknownErrno    = 0,
         EPERM           = libc::EPERM,
@@ -2244,6 +2250,7 @@ mod consts {
 mod consts {
     #[derive(Clone, Copy, Debug, Eq, PartialEq)]
     #[repr(i32)]
+    #[non_exhaustive]
     pub enum Errno {
         UnknownErrno = 0,
         EPERM = libc::EPERM,
@@ -2441,6 +2448,7 @@ mod consts {
 mod consts {
     #[derive(Clone, Copy, Debug, Eq, PartialEq)]
     #[repr(i32)]
+    #[non_exhaustive]
     pub enum Errno {
         UnknownErrno = 0,
         EPERM = libc::EPERM,

src/fcntl.rs

@@ -374,6 +374,7 @@ libc_bitflags!(
 
 #[cfg(not(target_os = "redox"))]
 #[derive(Debug, Eq, Hash, PartialEq)]
+#[non_exhaustive]
 pub enum FcntlArg<'a> {
     F_DUPFD(RawFd),
     F_DUPFD_CLOEXEC(RawFd),
@@ -405,6 +406,7 @@ pub enum FcntlArg<'a> {
 
 #[cfg(target_os = "redox")]
 #[derive(Debug, Clone, Copy, Eq, Hash, PartialEq)]
+#[non_exhaustive]
 pub enum FcntlArg {
     F_DUPFD(RawFd),
     F_DUPFD_CLOEXEC(RawFd),
@@ -454,6 +456,7 @@ pub fn fcntl(fd: RawFd, arg: FcntlArg) -> Result<c_int> {
 }
 
 #[derive(Clone, Copy, Debug, Eq, Hash, PartialEq)]
+#[non_exhaustive]
 pub enum FlockArg {
     LockShared,
     LockExclusive,
@@ -649,6 +652,7 @@ mod posix_fadvise {
 
     libc_enum! {
         #[repr(i32)]
+        #[non_exhaustive]
         pub enum PosixFadviseAdvice {
             POSIX_FADV_NORMAL,
             POSIX_FADV_SEQUENTIAL,

src/features.rs

@@ -97,7 +97,7 @@ mod os {
 #[cfg(any(target_os = "illumos"))]
 mod os {
     /// Check if the OS supports atomic close-on-exec for sockets
-    pub fn socket_atomic_cloexec() -> bool {
+    pub const fn socket_atomic_cloexec() -> bool {
         true
     }
 }
@@ -109,7 +109,7 @@ mod os {
           target_os = "solaris"))]
 mod os {
     /// Check if the OS supports atomic close-on-exec for sockets
-    pub fn socket_atomic_cloexec() -> bool {
+    pub const fn socket_atomic_cloexec() -> bool {
         false
     }
 }

src/mount/bsd.rs

@@ -111,7 +111,7 @@ impl NmountError {
     }
 
     /// Returns the inner [`Error`]
-    pub fn error(&self) -> Error {
+    pub const fn error(&self) -> Error {
         self.errno
     }
 

src/mqueue.rs

@@ -59,7 +59,7 @@ impl MqAttr {
         }
     }
 
-    pub fn flags(&self) -> mq_attr_member_t {
+    pub const fn flags(&self) -> mq_attr_member_t {
         self.mq_attr.mq_flags
     }
 }

src/poll.rs

@@ -25,7 +25,7 @@ pub struct PollFd {
 impl PollFd {
     /// Creates a new `PollFd` specifying the events of interest
     /// for a given file descriptor.
-    pub fn new(fd: RawFd, events: PollFlags) -> PollFd {
+    pub const fn new(fd: RawFd, events: PollFlags) -> PollFd {
         PollFd {
             pollfd: libc::pollfd {
                 fd,

src/sched.rs

@@ -97,7 +97,7 @@ mod sched_linux_like {
         }
 
         /// Return the maximum number of CPU in CpuSet
-        pub fn count() -> usize {
+        pub const fn count() -> usize {
             8 * mem::size_of::<libc::cpu_set_t>()
         }
     }

src/sys/aio.rs

@@ -39,6 +39,7 @@ libc_enum! {
     /// Mode for `AioCb::fsync`.  Controls whether only data or both data and
     /// metadata are synced.
     #[repr(i32)]
+    #[non_exhaustive]
     pub enum AioFsyncMode {
         /// do it like `fsync`
         O_SYNC,
@@ -57,6 +58,7 @@ libc_enum! {
     /// given `aiocb` should be used for a read operation, a write operation, or
     /// ignored.  Has no effect for any other aio functions.
     #[repr(i32)]
+    #[non_exhaustive]
     pub enum LioOpcode {
         LIO_NOP,
         LIO_WRITE,

src/sys/epoll.rs

@@ -29,6 +29,7 @@ libc_bitflags!(
 
 #[derive(Clone, Copy, Debug, Eq, Hash, PartialEq)]
 #[repr(i32)]
+#[non_exhaustive]
 pub enum EpollOp {
     EpollCtlAdd = libc::EPOLL_CTL_ADD,
     EpollCtlDel = libc::EPOLL_CTL_DEL,

src/sys/event.rs

@@ -36,6 +36,7 @@ type type_of_event_filter = i16;
 libc_enum! {
     #[cfg_attr(target_os = "netbsd", repr(u32))]
     #[cfg_attr(not(target_os = "netbsd"), repr(i16))]
+    #[non_exhaustive]
     pub enum EventFilter {
         EVFILT_AIO,
         /// Returns whenever there is no remaining data in the write buffer

src/sys/mman.rs

@@ -155,6 +155,7 @@ libc_enum!{
     ///
     /// Used by [`madvise`](./fn.madvise.html).
     #[repr(i32)]
+    #[non_exhaustive]
     pub enum MmapAdvise {
         /// No further special treatment. This is the default.
         MADV_NORMAL,

src/sys/ptrace/bsd.rs

@@ -24,6 +24,7 @@ cfg_if! {
 libc_enum! {
     #[repr(i32)]
     /// Ptrace Request enum defining the action to be taken.
+    #[non_exhaustive]
     pub enum Request {
         PT_TRACE_ME,
         PT_READ_I,

src/sys/ptrace/linux.rs

@@ -33,6 +33,7 @@ libc_enum!{
     #[cfg_attr(not(any(target_env = "musl", target_os = "android")), repr(u32))]
     #[cfg_attr(any(target_env = "musl", target_os = "android"), repr(i32))]
     /// Ptrace Request enum defining the action to be taken.
+    #[non_exhaustive]
     pub enum Request {
         PTRACE_TRACEME,
         PTRACE_PEEKTEXT,
@@ -123,6 +124,7 @@ libc_enum!{
     /// Using the ptrace options the tracer can configure the tracee to stop
     /// at certain events. This enum is used to define those events as defined
     /// in `man ptrace`.
+    #[non_exhaustive]
     pub enum Event {
         /// Event that stops before a return from fork or clone.
         PTRACE_EVENT_FORK,

src/sys/quota.rs

@@ -42,6 +42,7 @@ libc_enum!{
 libc_enum!{
     /// The scope of the quota.
     #[repr(i32)]
+    #[non_exhaustive]
     pub enum QuotaType {
         /// Specify a user quota
         USRQUOTA,
@@ -53,6 +54,7 @@ libc_enum!{
 libc_enum!{
     /// The type of quota format to use.
     #[repr(i32)]
+    #[non_exhaustive]
     pub enum QuotaFmt {
         /// Use the original quota format.
         QFMT_VFS_OLD,

src/sys/reboot.rs

@@ -12,6 +12,7 @@ libc_enum! {
     /// See [`set_cad_enabled()`](fn.set_cad_enabled.html) for
     /// enabling/disabling Ctrl-Alt-Delete.
     #[repr(i32)]
+    #[non_exhaustive]
     pub enum RebootMode {
         RB_HALT_SYSTEM,
         RB_KEXEC,

src/sys/signal.rs

@@ -23,6 +23,7 @@ libc_enum!{
     // We would prefer to use the libc::c_int alias in the repr attribute. Unfortunately
     // this is not (yet) possible.
     #[repr(i32)]
+    #[non_exhaustive]
     pub enum Signal {
         SIGHUP,
         SIGINT,
@@ -356,7 +357,7 @@ impl Iterator for SignalIterator {
 }
 
 impl Signal {
-    pub fn iterator() -> SignalIterator {
+    pub const fn iterator() -> SignalIterator {
         SignalIterator{next: 0}
     }
 }
@@ -396,6 +397,7 @@ libc_bitflags!{
 
 libc_enum! {
     #[repr(i32)]
+    #[non_exhaustive]
     pub enum SigmaskHow {
         SIG_BLOCK,
         SIG_UNBLOCK,