Auto merge of #47268 - EdSchouten:cloudabi-libstd, r=alexcrichton

Implement libstd for CloudABI.

Though CloudABI is strongly inspired by POSIX, its absence of features that don't work well with capability-based sandboxing makes it different enough that adding bits to `sys/unix` will make things a mess. This change therefore adds CloudABI specific platform code under `sys/cloudabi`.

One of the goals of this implementation is to build as much as possible directly on top of CloudABI's system call layer, as opposed to using the C library. This is preferred, as the system call layer is supposed to be stable, whereas the C library ABI technically is not. An advantage of this approach is that it allows us to implement certain interfaces, such as mutexes and condition variables more optimally. They can be lighter than the ones provided by pthreads.

This change disables some modules that cannot realistically be implemented right now. For example, libstd's pathname abstraction is not designed with POSIX `*at()` (e.g., `openat()`) in mind. The `*at()` functions are the only set of file system APIs available on CloudABI. There is no global file system namespace, nor a process working directory. Discussions on how to port these modules over are outside the scope of this change.

src/libstd/env.rs

@@ -956,8 +956,7 @@ mod arch {
 mod tests {
     use super::*;
 
-    use ffi::OsStr;
-    use path::{Path, PathBuf};
+    use path::Path;
 
     #[test]
     #[cfg_attr(target_os = "emscripten", ignore)]
@@ -980,6 +979,8 @@ mod tests {
     #[test]
     #[cfg(windows)]
     fn split_paths_windows() {
+        use path::PathBuf;
+
         fn check_parse(unparsed: &str, parsed: &[&str]) -> bool {
             split_paths(unparsed).collect::<Vec<_>>() ==
                 parsed.iter().map(|s| PathBuf::from(*s)).collect::<Vec<_>>()
@@ -1000,6 +1001,8 @@ mod tests {
     #[test]
     #[cfg(unix)]
     fn split_paths_unix() {
+        use path::PathBuf;
+
         fn check_parse(unparsed: &str, parsed: &[&str]) -> bool {
             split_paths(unparsed).collect::<Vec<_>>() ==
                 parsed.iter().map(|s| PathBuf::from(*s)).collect::<Vec<_>>()
@@ -1015,6 +1018,8 @@ mod tests {
     #[test]
     #[cfg(unix)]
     fn join_paths_unix() {
+        use ffi::OsStr;
+
         fn test_eq(input: &[&str], output: &str) -> bool {
             &*join_paths(input.iter().cloned()).unwrap() ==
                 OsStr::new(output)
@@ -1031,6 +1036,8 @@ mod tests {
     #[test]
     #[cfg(windows)]
     fn join_paths_windows() {
+        use ffi::OsStr;
+
         fn test_eq(input: &[&str], output: &str) -> bool {
             &*join_paths(input.iter().cloned()).unwrap() ==
                 OsStr::new(output)

src/libstd/fs.rs

@@ -1989,7 +1989,7 @@ impl AsInnerMut<fs_imp::DirBuilder> for DirBuilder {
     }
 }
 
-#[cfg(all(test, not(target_os = "emscripten")))]
+#[cfg(all(test, not(any(target_os = "cloudabi", target_os = "emscripten"))))]
 mod tests {
     use io::prelude::*;
 

src/libstd/net/tcp.rs

@@ -885,7 +885,7 @@ impl fmt::Debug for TcpListener {
     }
 }
 
-#[cfg(all(test, not(target_os = "emscripten")))]
+#[cfg(all(test, not(any(target_os = "cloudabi", target_os = "emscripten"))))]
 mod tests {
     use io::ErrorKind;
     use io::prelude::*;

src/libstd/net/udp.rs

@@ -786,7 +786,7 @@ impl fmt::Debug for UdpSocket {
     }
 }
 
-#[cfg(all(test, not(target_os = "emscripten")))]
+#[cfg(all(test, not(any(target_os = "cloudabi", target_os = "emscripten"))))]
 mod tests {
     use io::ErrorKind;
     use net::*;

src/libstd/process.rs

@@ -1392,7 +1392,7 @@ pub fn id() -> u32 {
     ::sys::os::getpid()
 }
 
-#[cfg(all(test, not(target_os = "emscripten")))]
+#[cfg(all(test, not(any(target_os = "cloudabi", target_os = "emscripten"))))]
 mod tests {
     use io::prelude::*;
 

src/libstd/sys/cloudabi/abi/bitflags.rs

@@ -0,0 +1,51 @@
+// Copyright (c) 2018 Nuxi (https://nuxi.nl/) and contributors.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions
+// are met:
+// 1. Redistributions of source code must retain the above copyright
+//    notice, this list of conditions and the following disclaimer.
+// 2. Redistributions in binary form must reproduce the above copyright
+//    notice, this list of conditions and the following disclaimer in the
+//    documentation and/or other materials provided with the distribution.
+//
+// THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+// ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+// ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+// FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+// DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+// OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+// HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+// LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+// OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+// SUCH DAMAGE.
+
+// Appease Rust's tidy.
+// ignore-license
+
+#[cfg(feature = "bitflags")]
+#[macro_use]
+extern crate bitflags;
+
+// Minimal implementation of bitflags! in case we can't depend on the bitflags
+// crate. Only implements `bits()` and a `from_bits_truncate()` that doesn't
+// actually truncate.
+#[cfg(not(feature = "bitflags"))]
+macro_rules! bitflags {
+  (
+    $(#[$attr:meta])*
+    pub struct $name:ident: $type:ty {
+      $($(#[$const_attr:meta])* const $const:ident = $val:expr;)*
+    }
+  ) => {
+    $(#[$attr])*
+    #[derive(Copy, Clone, Eq, PartialEq, Hash, Debug)]
+    pub struct $name { bits: $type }
+    impl $name {
+      $($(#[$const_attr])* pub const $const: $name = $name{ bits: $val };)*
+      pub fn bits(&self) -> $type { self.bits }
+      pub fn from_bits_truncate(bits: $type) -> Self { $name{ bits } }
+    }
+  }
+}