Merge pull request rust-lang#137 from rust-lang/fix/box-alloc-ice

Fix ice in box alloc

Author: antoyo

example/mini_core.rs

@@ -443,12 +443,22 @@ pub trait Deref {
     fn deref(&self) -> &Self::Target;
 }
 
+pub trait Allocator {
+}
+
+pub struct Global;
+
+impl Allocator for Global {}
+
 #[lang = "owned_box"]
-pub struct Box<T: ?Sized>(*mut T);
+pub struct Box<
+    T: ?Sized,
+    A: Allocator = Global,
+>(*mut T, A);
 
 impl<T: ?Sized + Unsize<U>, U: ?Sized> CoerceUnsized<Box<U>> for Box<T> {}
 
-impl<T: ?Sized> Drop for Box<T> {
+impl<T: ?Sized, A: Allocator> Drop for Box<T, A> {
     fn drop(&mut self) {
         // drop is currently performed by compiler.
     }
@@ -468,7 +478,7 @@ unsafe fn allocate(size: usize, _align: usize) -> *mut u8 {
 }
 
 #[lang = "box_free"]
-unsafe fn box_free<T: ?Sized>(ptr: *mut T) {
+unsafe fn box_free<T: ?Sized, A: Allocator>(ptr: *mut T, alloc: A) {
     libc::free(ptr as *mut u8);
 }
 

src/type_of.rs

@@ -251,7 +251,9 @@ impl<'tcx> LayoutGccExt<'tcx> for TyAndLayout<'tcx> {
             ty::Ref(..) | ty::RawPtr(_) => {
                 return self.field(cx, index).gcc_type(cx, true);
             }
-            ty::Adt(def, _) if def.is_box() => {
+            // only wide pointer boxes are handled as pointers
+            // thin pointer boxes with scalar allocators are handled by the general logic below
+            ty::Adt(def, substs) if def.is_box() && cx.layout_of(substs.type_at(1)).is_zst() => {
                 let ptr_ty = cx.tcx.mk_mut_ptr(self.ty.boxed_ty());
                 return cx.layout_of(ptr_ty).scalar_pair_element_gcc_type(cx, index, immediate);
             }