reorg: Introduce a posix/unistd module

Create a module for common Posix-specified definitions in `unistd.h`,
which are then reexported by relevant targets. Populate this with the
`STD{IN,OUT,ERR}_FILENO` constants to start, which have posix-specified
values.

Link: https://pubs.opengroup.org/onlinepubs/007904975/basedefs/unistd.h.html

Author: tgross35

src/fuchsia/mod.rs

@@ -1516,9 +1516,6 @@ pub const F_OK: c_int = 0;
 pub const R_OK: c_int = 4;
 pub const W_OK: c_int = 2;
 pub const X_OK: c_int = 1;
-pub const STDIN_FILENO: c_int = 0;
-pub const STDOUT_FILENO: c_int = 1;
-pub const STDERR_FILENO: c_int = 2;
 pub const SIGHUP: c_int = 1;
 pub const SIGINT: c_int = 2;
 pub const SIGQUIT: c_int = 3;

src/new/aix/mod.rs

@@ -2,3 +2,5 @@
 //!
 //! * Headers are not public
 //! * Manual pages: <https://www.ibm.com/docs/en/aix> (under "Technical reference" for that version)
+
+pub(crate) mod unistd;

src/new/aix/unistd.rs

@@ -0,0 +1,7 @@
+//! Header: `unistd.h`
+
+pub use crate::new::common::posix::unistd::{
+    STDERR_FILENO,
+    STDIN_FILENO,
+    STDOUT_FILENO,
+};

src/new/apple_libc/mod.rs

@@ -1,3 +1,6 @@
 //! Entrypoint for Apple headers, usually found as part of the Xcode SDK.
+//!
+//! <https://github.com/apple-oss-distributions/Libc/tree/main/include>
 
 pub(crate) mod signal;
+pub(crate) mod unistd;

src/new/apple_libc/unistd.rs

@@ -0,0 +1,7 @@
+//! Header: `unistd.h`
+
+pub use crate::new::common::posix::unistd::{
+    STDERR_FILENO,
+    STDIN_FILENO,
+    STDOUT_FILENO,
+};

src/new/bionic_libc/mod.rs

@@ -3,3 +3,4 @@
 //! <https://cs.android.com/android/platform/superproject/main/+/main:bionic/libc/include/>
 
 pub(crate) mod sys;
+pub(crate) mod unistd;

src/new/bionic_libc/unistd.rs

@@ -0,0 +1,7 @@
+//! Header: `unistd.h`
+
+pub use crate::new::common::posix::unistd::{
+    STDERR_FILENO,
+    STDIN_FILENO,
+    STDOUT_FILENO,
+};

src/new/common/mod.rs

@@ -16,23 +16,24 @@
     target_os = "netbsd",
     target_os = "openbsd",
 ))]
-mod bsd;
+pub(crate) mod bsd;
 
 #[cfg(any(
     target_os = "android",
     target_os = "emscripten",
     target_os = "l4re",
     target_os = "linux",
 ))]
-mod linux_like;
+pub(crate) mod linux_like;
 
 #[cfg(any(target_os = "dragonfly", target_os = "freebsd"))]
-mod freebsd_like;
+pub(crate) mod freebsd_like;
 
 #[cfg(any(target_os = "netbsd", target_os = "openbsd"))]
-mod netbsd_like;
+pub(crate) mod netbsd_like;
 
 #[cfg(any(target_os = "illumos", target_os = "solaris"))]
-mod solarish;
+pub(crate) mod solarish;
 
-mod posix;
+#[cfg(target_family = "unix")]
+pub(crate) mod posix;

src/new/common/posix/mod.rs

@@ -1 +1,3 @@
 //! POSIX APIs that are used by a number of platforms
+
+pub(crate) mod unistd;

src/new/common/posix/unistd.rs

@@ -0,0 +1,9 @@
+//! Header: `unistd.h`
+//!
+//! <https://pubs.opengroup.org/onlinepubs/007904975/basedefs/unistd.h.html>
+
+use crate::prelude::*;
+
+pub const STDIN_FILENO: c_int = 0;
+pub const STDOUT_FILENO: c_int = 1;
+pub const STDERR_FILENO: c_int = 2;