auto merge of rust-lang#12908 : alexcrichton/rust/issue-12897, r=thestinger

This is mostly just an implementation detail, and anyone worried about the stack
bounds doesn't need to be bothered with the red zone because it's not usable
anyway.

Closes rust-lang#12897

Author: bors

src/libgreen/task.rs

@@ -20,14 +20,15 @@
 
 use std::any::Any;
 use std::cast;
-use std::rt::env;
+use std::raw;
 use std::rt::Runtime;
+use std::rt::env;
 use std::rt::local::Local;
 use std::rt::rtio;
+use std::rt::stack;
 use std::rt::task::{Task, BlockedTask, SendMessage};
 use std::task::TaskOpts;
 use std::unstable::mutex::NativeMutex;
-use std::raw;
 
 use context::Context;
 use coroutine::Coroutine;
@@ -469,7 +470,9 @@ impl Runtime for GreenTask {
         let c = self.coroutine.as_ref()
             .expect("GreenTask.stack_bounds called without a coroutine");
 
-        (c.current_stack_segment.start() as uint,
+        // Don't return the red zone as part of the usable stack of this task,
+        // it's essentially an implementation detail.
+        (c.current_stack_segment.start() as uint + stack::RED_ZONE,
          c.current_stack_segment.end() as uint)
     }