4 files changed, 54 insertions, 3 deletions
diff --git a/src/libstd/sys_common/alloc.rs b/src/libstd/sys_common/alloc.rs
new file mode 100644
index 00000000000..439a9dfb3fd
--- /dev/null
+++ b/src/libstd/sys_common/alloc.rs
@@ -0,0 +1,50 @@
+// Copyright 2018 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#![allow(dead_code)]
+
+use alloc::{GlobalAlloc, Layout, System};
+use cmp;
+use ptr;
+
+// The minimum alignment guaranteed by the architecture. This value is used to
+// add fast paths for low alignment values.
+#[cfg(all(any(target_arch = "x86",
+              target_arch = "arm",
+              target_arch = "mips",
+              target_arch = "powerpc",
+              target_arch = "powerpc64",
+              target_arch = "asmjs",
+              target_arch = "wasm32")))]
+pub const MIN_ALIGN: usize = 8;
+#[cfg(all(any(target_arch = "x86_64",
+              target_arch = "aarch64",
+              target_arch = "mips64",
+              target_arch = "s390x",
+              target_arch = "sparc64")))]
+pub const MIN_ALIGN: usize = 16;
+
+pub unsafe fn realloc_fallback(
+    alloc: &System,
+    ptr: *mut u8,
+    old_layout: Layout,
+    new_size: usize,
+) -> *mut u8 {
+    // Docs for GlobalAlloc::realloc require this to be valid:
+    let new_layout = Layout::from_size_align_unchecked(new_size, old_layout.align());
+
+    let new_ptr = GlobalAlloc::alloc(alloc, new_layout);
+    if !new_ptr.is_null() {
+        let size = cmp::min(old_layout.size(), new_size);
+        ptr::copy_nonoverlapping(ptr, new_ptr, size);
+        GlobalAlloc::dealloc(alloc, ptr, old_layout);
+    }
+    new_ptr
+}
diff --git a/src/libstd/sys_common/mod.rs b/src/libstd/sys_common/mod.rs
index d0c4d6a7737..4b8cde3d1f4 100644
--- a/src/libstd/sys_common/mod.rs
+++ b/src/libstd/sys_common/mod.rs
@@ -38,6 +38,7 @@ macro_rules! rtassert {
     })
 }
 
+pub mod alloc;
 pub mod at_exit_imp;
 #[cfg(feature = "backtrace")]
 pub mod backtrace;
diff --git a/src/libstd/sys_common/poison.rs b/src/libstd/sys_common/poison.rs
index 1625efe4a2a..af93571a604 100644
--- a/src/libstd/sys_common/poison.rs
+++ b/src/libstd/sys_common/poison.rs
@@ -174,7 +174,7 @@ impl<T> PoisonError<T> {
     /// [`RwLock::read`]: ../../std/sync/struct.RwLock.html#method.read
     #[stable(feature = "sync_poison", since = "1.2.0")]
     pub fn new(guard: T) -> PoisonError<T> {
-        PoisonError { guard: guard }
+        PoisonError { guard }
     }
 
     /// Consumes this error indicating that a lock is poisoned, returning the
diff --git a/src/libstd/sys_common/wtf8.rs b/src/libstd/sys_common/wtf8.rs
index 8725abe7416..19ce932aa12 100644
--- a/src/libstd/sys_common/wtf8.rs
+++ b/src/libstd/sys_common/wtf8.rs
@@ -67,7 +67,7 @@ impl CodePoint {
     /// Only use when `value` is known to be less than or equal to 0x10FFFF.
     #[inline]
     pub unsafe fn from_u32_unchecked(value: u32) -> CodePoint {
-        CodePoint { value: value }
+        CodePoint { value }
     }
 
     /// Creates a new `CodePoint` if the value is a valid code point.
@@ -76,7 +76,7 @@ impl CodePoint {
     #[inline]
     pub fn from_u32(value: u32) -> Option<CodePoint> {
         match value {
-            0 ..= 0x10FFFF => Some(CodePoint { value: value }),
+            0 ..= 0x10FFFF => Some(CodePoint { value }),
             _ => None
         }
     }