std: Delete the `alloc_system` crate

This commit deletes the `alloc_system` crate from the standard
distribution. This unstable crate is no longer needed in the modern
stable global allocator world, but rather its functionality is folded
directly into the standard library. The standard library was already the
only stable location to access this crate, and as a result this should
not affect any stable code.

2 files changed, 51 insertions, 0 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;