2 files changed, 16 insertions, 21 deletions

diff --git a/src/libstd/rt/unwind.rs b/src/libstd/rt/unwind.rs
index e0c512706e6..8d7713d0558 100644
--- a/src/libstd/rt/unwind.rs
+++ b/src/libstd/rt/unwind.rs
@@ -493,27 +493,16 @@ pub extern fn rust_begin_unwind(msg: fmt::Arguments,
 /// the actual formatting into this shared place.
 #[inline(never)] #[cold]
 pub fn begin_unwind_fmt(msg: fmt::Arguments, file_line: &(&'static str, uint)) -> ! {
-    use fmt::FormatWriter;
+    use fmt::Writer;
 
     // We do two allocations here, unfortunately. But (a) they're
     // required with the current scheme, and (b) we don't handle
     // panic + OOM properly anyway (see comment in begin_unwind
     // below).
 
-    struct VecWriter<'a> { v: &'a mut Vec<u8> }
-
-    impl<'a> fmt::FormatWriter for VecWriter<'a> {
-        fn write(&mut self, buf: &[u8]) -> fmt::Result {
-            self.v.push_all(buf);
-            Ok(())
-        }
-    }
-
-    let mut v = Vec::new();
-    let _ = write!(&mut VecWriter { v: &mut v }, "{}", msg);
-
-    let msg = box String::from_utf8_lossy(v.as_slice()).into_owned();
-    begin_unwind_inner(msg, file_line)
+    let mut s = String::new();
+    let _ = write!(&mut s, "{}", msg);
+    begin_unwind_inner(box s, file_line)
 }
 
 /// This is the entry point of unwinding for panic!() and assert!().
diff --git a/src/libstd/rt/util.rs b/src/libstd/rt/util.rs
index fee86e33455..fa7c305d69e 100644
--- a/src/libstd/rt/util.rs
+++ b/src/libstd/rt/util.rs
@@ -96,8 +96,8 @@ pub const Stdout: Stdio = Stdio(libc::STDOUT_FILENO);
 #[allow(non_upper_case_globals)]
 pub const Stderr: Stdio = Stdio(libc::STDERR_FILENO);
 
-impl fmt::FormatWriter for Stdio {
-    fn write(&mut self, data: &[u8]) -> fmt::Result {
+impl Stdio {
+    pub fn write_bytes(&mut self, data: &[u8]) {
         #[cfg(unix)]
         type WriteLen = libc::size_t;
         #[cfg(windows)]
@@ -108,6 +108,12 @@ impl fmt::FormatWriter for Stdio {
                         data.as_ptr() as *const libc::c_void,
                         data.len() as WriteLen);
         }
+    }
+}
+
+impl fmt::Writer for Stdio {
+    fn write_str(&mut self, data: &str) -> fmt::Result {
+        self.write_bytes(data.as_bytes());
         Ok(()) // yes, we're lying
     }
 }
@@ -117,16 +123,16 @@ pub fn dumb_print(args: fmt::Arguments) {
 }
 
 pub fn abort(args: fmt::Arguments) -> ! {
-    use fmt::FormatWriter;
+    use fmt::Writer;
 
     struct BufWriter<'a> {
         buf: &'a mut [u8],
         pos: uint,
     }
-    impl<'a> FormatWriter for BufWriter<'a> {
-        fn write(&mut self, bytes: &[u8]) -> fmt::Result {
+    impl<'a> fmt::Writer for BufWriter<'a> {
+        fn write_str(&mut self, bytes: &str) -> fmt::Result {
             let left = self.buf.slice_from_mut(self.pos);
-            let to_write = bytes[..cmp::min(bytes.len(), left.len())];
+            let to_write = bytes.as_bytes()[..cmp::min(bytes.len(), left.len())];
             slice::bytes::copy_memory(left, to_write);
             self.pos += to_write.len();
             Ok(())