Trim down alloc_system.rs

It is used only by a single test. Also remove the dependency on the libc
crate.

example/alloc_system.rs

@@ -8,33 +8,21 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 #![no_std]
-#![feature(allocator_api, rustc_private)]
-#![cfg_attr(any(unix, target_os = "redox"), feature(libc))]
-
-// 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")))]
-const MIN_ALIGN: usize = 8;
-#[cfg(all(any(target_arch = "x86_64",
-              target_arch = "aarch64",
-              target_arch = "mips64",
-              target_arch = "s390x",
-              target_arch = "sparc64")))]
-const MIN_ALIGN: usize = 16;
 
 pub struct System;
+
 #[cfg(any(windows, unix, target_os = "redox"))]
 mod realloc_fallback {
     use core::alloc::{GlobalAlloc, Layout};
     use core::cmp;
     use core::ptr;
     impl super::System {
-        pub(crate) unsafe fn realloc_fallback(&self, ptr: *mut u8, old_layout: Layout,
+        pub(crate) unsafe fn realloc_fallback(
-                                              new_size: usize) -> *mut u8 {
+            &self,
+            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(self, new_layout);
@@ -49,97 +37,47 @@ mod realloc_fallback {
 }
 #[cfg(any(unix, target_os = "redox"))]
 mod platform {
-    extern crate libc;
-    use core::ptr;
-    use MIN_ALIGN;
-    use System;
     use core::alloc::{GlobalAlloc, Layout};
+    use core::ffi::c_void;
+    use core::ptr;
+    use System;
+    extern "C" {
+        fn posix_memalign(memptr: *mut *mut c_void, align: usize, size: usize) -> i32;
+        fn free(p: *mut c_void);
+    }
     unsafe impl GlobalAlloc for System {
         #[inline]
         unsafe fn alloc(&self, layout: Layout) -> *mut u8 {
-            if layout.align() <= MIN_ALIGN && layout.align() <= layout.size() {
+            aligned_malloc(&layout)
-                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() {
+            let ptr = self.alloc(layout.clone());
-                libc::calloc(layout.size(), 1) as *mut u8
+            if !ptr.is_null() {
-            } else {
+                ptr::write_bytes(ptr, 0, layout.size());
-                let ptr = self.alloc(layout.clone());
-                if !ptr.is_null() {
-                    ptr::write_bytes(ptr, 0, layout.size());
-                }
-                ptr
             }
+            ptr
         }
         #[inline]
         unsafe fn dealloc(&self, ptr: *mut u8, _layout: Layout) {
-            libc::free(ptr as *mut libc::c_void)
+            free(ptr as *mut 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 {
+            self.realloc_fallback(ptr, layout, new_size)
-                libc::realloc(ptr as *mut libc::c_void, new_size) as *mut u8
-            } else {
-                self.realloc_fallback(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());
+        let ret = posix_memalign(&mut out, layout.align(), layout.size());
-        if ret != 0 {
+        if ret != 0 { ptr::null_mut() } else { out as *mut u8 }
-            ptr::null_mut()
-        } else {
-            out as *mut u8
-        }
     }
 }
 #[cfg(windows)]
 #[allow(nonstandard_style)]
 mod platform {
-    use MIN_ALIGN;
-    use System;
     use core::alloc::{GlobalAlloc, Layout};
+    use System;
     type LPVOID = *mut u8;
     type HANDLE = LPVOID;
     type SIZE_T = usize;
@@ -165,18 +103,9 @@ mod platform {
     }
     #[inline]
     unsafe fn allocate_with_flags(layout: Layout, flags: DWORD) -> *mut u8 {
-        let ptr = if layout.align() <= MIN_ALIGN {
+        let size = layout.size() + layout.align();
-            HeapAlloc(GetProcessHeap(), flags, layout.size())
+        let ptr = HeapAlloc(GetProcessHeap(), flags, size);
-        } else {
+        (if ptr.is_null() { ptr } else { align_ptr(ptr, layout.align()) }) as *mut u8
-            let size = layout.size() + layout.align();
-            let ptr = HeapAlloc(GetProcessHeap(), flags, size);
-            if ptr.is_null() {
-                ptr
-            } else {
-                align_ptr(ptr, layout.align())
-            }
-        };
-        ptr as *mut u8
     }
     unsafe impl GlobalAlloc for System {
         #[inline]
@@ -189,24 +118,13 @@ mod platform {
         }
         #[inline]
         unsafe fn dealloc(&self, ptr: *mut u8, layout: Layout) {
-            if layout.align() <= MIN_ALIGN {
+            let header = get_header(ptr);
-                let err = HeapFree(GetProcessHeap(), 0, ptr as LPVOID);
+            let err = HeapFree(GetProcessHeap(), 0, header.0 as LPVOID);
-                debug_assert!(err != 0, "Failed to free heap memory: {}",
+            debug_assert!(err != 0, "Failed to free heap memory: {}", GetLastError());
-                              GetLastError());
-            } else {
-                let header = get_header(ptr);
-                let err = HeapFree(GetProcessHeap(), 0, header.0 as LPVOID);
-                debug_assert!(err != 0, "Failed to free heap memory: {}",
-                              GetLastError());
-            }
         }
         #[inline]
         unsafe fn realloc(&self, ptr: *mut u8, layout: Layout, new_size: usize) -> *mut u8 {
-            if layout.align() <= MIN_ALIGN {
+            self.realloc_fallback(ptr, layout, new_size)
-                HeapReAlloc(GetProcessHeap(), 0, ptr as LPVOID, new_size) as *mut u8
-            } else {
-                self.realloc_fallback(ptr, layout, new_size)
-            }
         }
     }
 }