Add FIO(N)CLEX ioctl (#1400)

Author: rusty-snake

src/backend/linux_raw/c.rs

@@ -10,7 +10,7 @@ pub(crate) type size_t = usize;
 pub(crate) use linux_raw_sys::ctypes::*;
 pub(crate) use linux_raw_sys::errno::{EBADF, EINVAL};
 pub(crate) use linux_raw_sys::general::{__kernel_fd_set as fd_set, __FD_SETSIZE as FD_SETSIZE};
-pub(crate) use linux_raw_sys::ioctl::{FIONBIO, FIONREAD};
+pub(crate) use linux_raw_sys::ioctl::{FIOCLEX, FIONBIO, FIONCLEX, FIONREAD};
 // Import the kernel's `uid_t` and `gid_t` if they're 32-bit.
 #[cfg(feature = "thread")]
 pub(crate) use linux_raw_sys::general::futex_waitv;

src/io/ioctl.rs

@@ -16,7 +16,10 @@ use backend::fd::AsFd;
 ///
 /// This is similar to `fcntl(fd, F_SETFD, FD_CLOEXEC)`, except that it avoids
 /// clearing any other flags that might be set.
-#[cfg(apple)]
+///
+/// Linux: Note that `ioctl` can not be used on `OFlags::PATH` file
+/// descriptors.
+#[cfg(any(apple, linux_kernel))]
 #[inline]
 #[doc(alias = "FIOCLEX")]
 #[doc(alias = "FD_CLOEXEC")]
@@ -28,6 +31,24 @@ pub fn ioctl_fioclex<Fd: AsFd>(fd: Fd) -> io::Result<()> {
     }
 }
 
+/// `ioctl(fd, FIONCLEX, NULL)`—Remove the close-on-exec flag.
+///
+/// This is similar to `fcntl_setfd(fd, FdFlags::empty())`, except that it avoids
+/// clearing any other flags that might be set.
+///
+/// Linux: Note that `ioctl` can not be used on `OFlags::PATH` file
+/// descriptors.
+#[cfg(any(apple, linux_kernel))]
+#[inline]
+#[doc(alias = "FIONCLEX")]
+pub fn ioctl_fionclex<Fd: AsFd>(fd: Fd) -> io::Result<()> {
+    // SAFETY: `FIONCLEX` is a no-argument setter opcode.
+    unsafe {
+        let ctl = ioctl::NoArg::<{ c::FIONCLEX }>::new();
+        ioctl::ioctl(fd, ctl)
+    }
+}
+
 /// `ioctl(fd, FIONBIO, &value)`—Enables or disables non-blocking mode.
 ///
 /// # References