Auto merge of #55660 - alexcrichton:cleanup-alloc-system, r=dtolnay,SimonSapin

Remove the `alloc_system` crate

In what's hopefully one of the final nails in the coffin of the "old allocator story of yore" this PR deletes the `alloc_system` crate and all traces of it from the compiler. The compiler no longer needs to inject allocator crates anywhere and the `alloc_system` crate has no real reason to exist outside the standard library.

The unstable `alloc_system` crate is folded directly into the standard library where its stable interface, the `System` type, remains the same. All unstable traces of `alloc_system` are removed, however.

1 files changed, 100 insertions, 0 deletions

diff --git a/src/libstd/sys/unix/alloc.rs b/src/libstd/sys/unix/alloc.rs
new file mode 100644
index 00000000000..2a7f1934518
--- /dev/null
+++ b/src/libstd/sys/unix/alloc.rs
@@ -0,0 +1,100 @@
+// 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.
+
+use ptr;
+use libc;
+use sys_common::alloc::{MIN_ALIGN, realloc_fallback};
+use alloc::{GlobalAlloc, Layout, System};
+
+#[stable(feature = "alloc_system_type", since = "1.28.0")]
+unsafe impl GlobalAlloc for System {
+    #[inline]
+    unsafe fn alloc(&self, layout: Layout) -> *mut u8 {
+        if layout.align() <= MIN_ALIGN && layout.align() <= layout.size() {
+            libc::malloc(layout.size()) as *mut u8
+        } else {
+            #[cfg(target_os = "macos")]
+            {
+                if layout.align() > (1 << 31) {
+                    return ptr::null_mut()
+                }
+            }
+            aligned_malloc(&layout)
+        }
+    }
+
+    #[inline]
+    unsafe fn alloc_zeroed(&self, layout: Layout) -> *mut u8 {
+        if layout.align() <= MIN_ALIGN && layout.align() <= layout.size() {
+            libc::calloc(layout.size(), 1) as *mut u8
+        } else {
+            let ptr = self.alloc(layout.clone());
+            if !ptr.is_null() {
+                ptr::write_bytes(ptr, 0, layout.size());
+            }
+            ptr
+        }
+    }
+
+    #[inline]
+    unsafe fn dealloc(&self, ptr: *mut u8, _layout: Layout) {
+        libc::free(ptr as *mut libc::c_void)
+    }
+
+    #[inline]
+    unsafe fn realloc(&self, ptr: *mut u8, layout: Layout, new_size: usize) -> *mut u8 {
+        if layout.align() <= MIN_ALIGN && layout.align() <= new_size {
+            libc::realloc(ptr as *mut libc::c_void, new_size) as *mut u8
+        } else {
+            realloc_fallback(self, ptr, layout, new_size)
+        }
+    }
+}
+
+#[cfg(any(target_os = "android",
+          target_os = "hermit",
+          target_os = "redox",
+          target_os = "solaris"))]
+#[inline]
+unsafe fn aligned_malloc(layout: &Layout) -> *mut u8 {
+    // On android we currently target API level 9 which unfortunately
+    // doesn't have the `posix_memalign` API used below. Instead we use
+    // `memalign`, but this unfortunately has the property on some systems
+    // where the memory returned cannot be deallocated by `free`!
+    //
+    // Upon closer inspection, however, this appears to work just fine with
+    // Android, so for this platform we should be fine to call `memalign`
+    // (which is present in API level 9). Some helpful references could
+    // possibly be chromium using memalign [1], attempts at documenting that
+    // memalign + free is ok [2] [3], or the current source of chromium
+    // which still uses memalign on android [4].
+    //
+    // [1]: https://codereview.chromium.org/10796020/
+    // [2]: https://code.google.com/p/android/issues/detail?id=35391
+    // [3]: https://bugs.chromium.org/p/chromium/issues/detail?id=138579
+    // [4]: https://chromium.googlesource.com/chromium/src/base/+/master/
+    //                                       /memory/aligned_memory.cc
+    libc::memalign(layout.align(), layout.size()) as *mut u8
+}
+
+#[cfg(not(any(target_os = "android",
+              target_os = "hermit",
+              target_os = "redox",
+              target_os = "solaris")))]
+#[inline]
+unsafe fn aligned_malloc(layout: &Layout) -> *mut u8 {
+    let mut out = ptr::null_mut();
+    let ret = libc::posix_memalign(&mut out, layout.align(), layout.size());
+    if ret != 0 {
+        ptr::null_mut()
+    } else {
+        out as *mut u8
+    }
+}