Rewrite boxed_region/memory_region in Rust

This drops more of the old C++ runtime to rather be written in rust. A few
features were lost along the way, but hopefully not too many. The main loss is
that there are no longer backtraces associated with allocations (rust doesn't
have a way of acquiring those just yet). Other than that though, I believe that
the rest of the debugging utilities made their way over into rust.

Closes #8704

mk/rt.mk

@@ -89,8 +89,6 @@ RUNTIME_CXXS_$(1)_$(2) := \
               rt/rust_upcall.cpp \
               rt/rust_uv.cpp \
               rt/miniz.cpp \
-              rt/memory_region.cpp \
-              rt/boxed_region.cpp \
               rt/rust_android_dummy.cpp \
               rt/rust_test_helpers.cpp
 

src/libstd/at_vec.rs

@@ -158,7 +158,6 @@ pub mod raw {
     use at_vec::capacity;
     use cast;
     use cast::{transmute, transmute_copy};
-    use libc;
     use ptr;
     use mem;
     use uint;
@@ -250,7 +249,7 @@ pub mod raw {
             use rt::task::Task;
 
             do Local::borrow |task: &mut Task| {
-                task.heap.realloc(ptr as *libc::c_void, size) as *()
+                task.heap.realloc(ptr as *mut Box<()>, size) as *()
             }
         }
     }

src/libstd/cleanup.rs

@@ -11,7 +11,7 @@
 #[doc(hidden)];
 
 use libc::c_void;
-use ptr::null;
+use ptr;
 use unstable::intrinsics::TyDesc;
 use unstable::raw;
 
@@ -37,7 +37,7 @@ unsafe fn each_live_alloc(read_next_before: bool,
     use rt::local_heap;
 
     let mut box = local_heap::live_allocs();
-    while box != null() {
+    while box != ptr::mut_null() {
         let next_before = (*box).next;
         let uniq = (*box).ref_count == managed::RC_MANAGED_UNIQUE;
 

src/libstd/rt/env.rs

@@ -19,6 +19,7 @@ use os;
 
 static mut MIN_STACK: uint = 4000000;
 static mut DEBUG_BORROW: bool = false;
+static mut POISON_ON_FREE: bool = false;
 
 pub fn init() {
     unsafe {
@@ -33,6 +34,10 @@ pub fn init() {
             Some(_) => DEBUG_BORROW = true,
             None => ()
         }
+        match os::getenv("RUST_POISON_ON_FREE") {
+            Some(_) => POISON_ON_FREE = true,
+            None => ()
+        }
     }
 }
 
@@ -43,3 +48,7 @@ pub fn min_stack() -> uint {
 pub fn debug_borrow() -> bool {
     unsafe { DEBUG_BORROW }
 }
+
+pub fn poison_on_free() -> bool {
+    unsafe { POISON_ON_FREE }
+}

src/libstd/rt/global_heap.rs

@@ -19,7 +19,7 @@ extern {
 }
 
 #[inline]
-fn get_box_size(body_size: uint, body_align: uint) -> uint {
+pub fn get_box_size(body_size: uint, body_align: uint) -> uint {
     let header_size = size_of::<raw::Box<()>>();
     // FIXME (#2699): This alignment calculation is suspicious. Is it right?
     let total_size = align_to(header_size, body_align) + body_size;