Use boxed functions instead of transmute

... to convert between Box and raw pointers. E. g. use

```
let b: Box<Foo> = Box::from_raw(p);
```

instead of

```
let b: Box<Foo> = mem::transmute(p);
```

Patch also changes closure release code in `src/libstd/sys/unix/thread.rs`
when `pthread_create` failed. Raw pointer was transmuted to box of
`FnOnce()` instead of `Thunk`. This code was probably never executed,
because `pthread_create` rarely fails in practice.

2 files changed, 4 insertions, 4 deletions

diff --git a/src/libstd/sys/common/helper_thread.rs b/src/libstd/sys/common/helper_thread.rs
index dc1ae85efe0..5faaa928ee9 100644
--- a/src/libstd/sys/common/helper_thread.rs
+++ b/src/libstd/sys/common/helper_thread.rs
@@ -22,8 +22,8 @@
 
 use prelude::v1::*;
 
+use boxed;
 use cell::UnsafeCell;
-use mem;
 use ptr;
 use rt;
 use sync::{StaticMutex, StaticCondvar};
@@ -88,7 +88,7 @@ impl<M: Send> Helper<M> {
             let _guard = self.lock.lock().unwrap();
             if !*self.initialized.get() {
                 let (tx, rx) = channel();
-                *self.chan.get() = mem::transmute(box tx);
+                *self.chan.get() = boxed::into_raw(box tx);
                 let (receive, send) = helper_signal::new();
                 *self.signal.get() = send as uint;
 
@@ -132,7 +132,7 @@ impl<M: Send> Helper<M> {
             let mut guard = self.lock.lock().unwrap();
 
             // Close the channel by destroying it
-            let chan: Box<Sender<M>> = mem::transmute(*self.chan.get());
+            let chan: Box<Sender<M>> = Box::from_raw(*self.chan.get());
             *self.chan.get() = ptr::null_mut();
             drop(chan);
             helper_signal::signal(*self.signal.get() as helper_signal::signal);
diff --git a/src/libstd/sys/common/thread.rs b/src/libstd/sys/common/thread.rs
index b725b6c7e6e..731617858e9 100644
--- a/src/libstd/sys/common/thread.rs
+++ b/src/libstd/sys/common/thread.rs
@@ -27,7 +27,7 @@ pub fn start_thread(main: *mut libc::c_void) -> thread::rust_thread_return {
     unsafe {
         stack::record_os_managed_stack_bounds(0, usize::MAX);
         let handler = stack_overflow::Handler::new();
-        let f: Box<Thunk> = mem::transmute(main);
+        let f: Box<Thunk> = Box::from_raw(main as *mut Thunk);
         f.invoke(());
         drop(handler);
         mem::transmute(0 as thread::rust_thread_return)