Auto merge of #43972 - TobiasSchaffner:std_clean, r=alexcrichton

 Add the libstd-modifications needed for the L4Re target

This commit adds the needed modifications to compile the std crate for the L4 Runtime environment (L4Re).

A target for the L4Re was introduced in commit: c151220a84e40b65e45308cc0f3bbea4466d3acf

In many aspects implementations for linux also apply for the L4Re microkernel.

Some uncommon characteristics had to be resolved:
 * L4Re has no network funktionality
 * L4Re has a maximum stacksize of 1Mb for threads
 * L4Re has no uid or gid

Co-authored-by: Sebastian Humenda <sebastian.humenda@tu-dresden.de>

4 files changed, 24 insertions, 22 deletions

diff --git a/src/libstd/sys_common/mod.rs b/src/libstd/sys_common/mod.rs
index 30241819bd5..d7654ce9300 100644
--- a/src/libstd/sys_common/mod.rs
+++ b/src/libstd/sys_common/mod.rs
@@ -44,10 +44,10 @@ pub mod thread_local;
 pub mod util;
 pub mod wtf8;
 
-#[cfg(target_os = "redox")]
+#[cfg(any(target_os = "redox", target_os = "l4re"))]
 pub use sys::net;
 
-#[cfg(not(target_os = "redox"))]
+#[cfg(not(any(target_os = "redox", target_os = "l4re")))]
 pub mod net;
 
 #[cfg(feature = "backtrace")]
diff --git a/src/libstd/sys_common/net.rs b/src/libstd/sys_common/net.rs
index 1ca39ff9d4a..19dc841b9b5 100644
--- a/src/libstd/sys_common/net.rs
+++ b/src/libstd/sys_common/net.rs
@@ -24,22 +24,22 @@ use time::Duration;
 #[cfg(any(target_os = "dragonfly", target_os = "freebsd",
           target_os = "ios", target_os = "macos",
           target_os = "openbsd", target_os = "netbsd",
-          target_os = "solaris", target_os = "haiku"))]
+          target_os = "solaris", target_os = "haiku", target_os = "l4re"))]
 use sys::net::netc::IPV6_JOIN_GROUP as IPV6_ADD_MEMBERSHIP;
 #[cfg(not(any(target_os = "dragonfly", target_os = "freebsd",
               target_os = "ios", target_os = "macos",
               target_os = "openbsd", target_os = "netbsd",
-              target_os = "solaris", target_os = "haiku")))]
+              target_os = "solaris", target_os = "haiku", target_os = "l4re")))]
 use sys::net::netc::IPV6_ADD_MEMBERSHIP;
 #[cfg(any(target_os = "dragonfly", target_os = "freebsd",
           target_os = "ios", target_os = "macos",
           target_os = "openbsd", target_os = "netbsd",
-          target_os = "solaris", target_os = "haiku"))]
+          target_os = "solaris", target_os = "haiku", target_os = "l4re"))]
 use sys::net::netc::IPV6_LEAVE_GROUP as IPV6_DROP_MEMBERSHIP;
 #[cfg(not(any(target_os = "dragonfly", target_os = "freebsd",
               target_os = "ios", target_os = "macos",
               target_os = "openbsd", target_os = "netbsd",
-              target_os = "solaris", target_os = "haiku")))]
+              target_os = "solaris", target_os = "haiku", target_os = "l4re")))]
 use sys::net::netc::IPV6_DROP_MEMBERSHIP;
 
 #[cfg(any(target_os = "linux", target_os = "android",
diff --git a/src/libstd/sys_common/thread.rs b/src/libstd/sys_common/thread.rs
index 3ee160da5fa..87fb34a9dec 100644
--- a/src/libstd/sys_common/thread.rs
+++ b/src/libstd/sys_common/thread.rs
@@ -8,9 +8,12 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+use env;
 use alloc::boxed::FnBox;
 use libc;
+use sync::atomic::{self, Ordering};
 use sys::stack_overflow;
+use sys::thread as imp;
 
 pub unsafe fn start_thread(main: *mut libc::c_void) {
     // Next, set up our stack overflow handler which may get triggered if we run
@@ -20,3 +23,18 @@ pub unsafe fn start_thread(main: *mut libc::c_void) {
     // Finally, let's run some code.
     Box::from_raw(main as *mut Box<FnBox()>)()
 }
+
+pub fn min_stack() -> usize {
+    static MIN: atomic::AtomicUsize = atomic::AtomicUsize::new(0);
+    match MIN.load(Ordering::SeqCst) {
+        0 => {}
+        n => return n - 1,
+    }
+    let amt = env::var("RUST_MIN_STACK").ok().and_then(|s| s.parse().ok());
+    let amt = amt.unwrap_or(imp::DEFAULT_MIN_STACK_SIZE);
+
+    // 0 is our sentinel value, so ensure that we'll never see 0 after
+    // initialization has run
+    MIN.store(amt + 1, Ordering::SeqCst);
+    amt
+}
diff --git a/src/libstd/sys_common/util.rs b/src/libstd/sys_common/util.rs
index daa0c15920b..a391c7cc6ef 100644
--- a/src/libstd/sys_common/util.rs
+++ b/src/libstd/sys_common/util.rs
@@ -8,27 +8,11 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use env;
 use fmt;
 use io::prelude::*;
-use sync::atomic::{self, Ordering};
 use sys::stdio::Stderr;
 use thread;
 
-pub fn min_stack() -> usize {
-    static MIN: atomic::AtomicUsize = atomic::AtomicUsize::new(0);
-    match MIN.load(Ordering::SeqCst) {
-        0 => {}
-        n => return n - 1,
-    }
-    let amt = env::var("RUST_MIN_STACK").ok().and_then(|s| s.parse().ok());
-    let amt = amt.unwrap_or(2 * 1024 * 1024);
-    // 0 is our sentinel value, so ensure that we'll never see 0 after
-    // initialization has run
-    MIN.store(amt + 1, Ordering::SeqCst);
-    amt
-}
-
 pub fn dumb_print(args: fmt::Arguments) {
     let _ = Stderr::new().map(|mut stderr| stderr.write_fmt(args));
 }