miri: allocation is infallible

Author: RalfJung

src/librustc_mir/const_eval.rs

@@ -187,7 +187,7 @@ fn eval_body_using_ecx<'mir, 'tcx>(
     }
     let layout = ecx.layout_of(mir.return_ty().subst(tcx, cid.instance.substs))?;
     assert!(!layout.is_unsized());
-    let ret = ecx.allocate(layout, MemoryKind::Stack)?;
+    let ret = ecx.allocate(layout, MemoryKind::Stack);
 
     let name = ty::tls::with(|tcx| tcx.item_path_str(cid.instance.def_id()));
     let prom = cid.promoted.map_or(String::new(), |p| format!("::promoted[{:?}]", p));
@@ -490,8 +490,8 @@ impl<'a, 'mir, 'tcx> interpret::Machine<'a, 'mir, 'tcx>
         _ecx: &mut EvalContext<'a, 'mir, 'tcx, Self>,
         ptr: Pointer,
         _kind: MemoryKind<Self::MemoryKinds>,
-    ) -> EvalResult<'tcx, Pointer> {
-        Ok(ptr)
+    ) -> Pointer {
+        ptr
     }
 
     #[inline(always)]

src/librustc_mir/interpret/machine.rs

@@ -185,7 +185,7 @@ pub trait Machine<'a, 'mir, 'tcx>: Sized {
         ecx: &mut EvalContext<'a, 'mir, 'tcx, Self>,
         ptr: Pointer,
         kind: MemoryKind<Self::MemoryKinds>,
-    ) -> EvalResult<'tcx, Pointer<Self::PointerTag>>;
+    ) -> Pointer<Self::PointerTag>;
 
     /// Executed when evaluating the `*` operator: Following a reference.
     /// This has the chance to adjust the tag.  It should not change anything else!

src/librustc_mir/interpret/memory.rs

@@ -131,20 +131,20 @@ impl<'a, 'mir, 'tcx, M: Machine<'a, 'mir, 'tcx>> Memory<'a, 'mir, 'tcx, M> {
         &mut self,
         alloc: Allocation<M::PointerTag, M::AllocExtra>,
         kind: MemoryKind<M::MemoryKinds>,
-    ) -> EvalResult<'tcx, AllocId> {
+    ) -> AllocId {
         let id = self.tcx.alloc_map.lock().reserve();
         self.alloc_map.insert(id, (kind, alloc));
-        Ok(id)
+        id
     }
 
     pub fn allocate(
         &mut self,
         size: Size,
         align: Align,
         kind: MemoryKind<M::MemoryKinds>,
-    ) -> EvalResult<'tcx, Pointer> {
+    ) -> Pointer {
         let extra = AllocationExtra::memory_allocated(size, &self.extra);
-        Ok(Pointer::from(self.allocate_with(Allocation::undef(size, align, extra), kind)?))
+        Pointer::from(self.allocate_with(Allocation::undef(size, align, extra), kind))
     }
 
     pub fn reallocate(
@@ -162,7 +162,7 @@ impl<'a, 'mir, 'tcx, M: Machine<'a, 'mir, 'tcx>> Memory<'a, 'mir, 'tcx, M> {
 
         // For simplicities' sake, we implement reallocate as "alloc, copy, dealloc".
         // This happens so rarely, the perf advantage is outweighed by the maintenance cost.
-        let new_ptr = self.allocate(new_size, new_align, kind)?;
+        let new_ptr = self.allocate(new_size, new_align, kind);
         self.copy(
             ptr.into(),
             old_align,

src/librustc_mir/interpret/operand.rs

@@ -382,7 +382,7 @@ impl<'a, 'mir, 'tcx, M: Machine<'a, 'mir, 'tcx>> EvalContext<'a, 'mir, 'tcx, M>
             _ => {
                 trace!("Forcing allocation for local of type {:?}", layout.ty);
                 Operand::Indirect(
-                    *self.allocate(layout, MemoryKind::Stack)?
+                    *self.allocate(layout, MemoryKind::Stack)
                 )
             }
         })

src/librustc_mir/interpret/place.rs

@@ -911,7 +911,7 @@ where
                         // that might e.g., be an inner field of a struct with `Scalar` layout,
                         // that has different alignment than the outer field.
                         let local_layout = self.layout_of_local(&self.stack[frame], local)?;
-                        let ptr = self.allocate(local_layout, MemoryKind::Stack)?;
+                        let ptr = self.allocate(local_layout, MemoryKind::Stack);
                         // We don't have to validate as we can assume the local
                         // was already valid for its type.
                         self.write_immediate_to_mplace_no_validate(value, ptr)?;
@@ -933,15 +933,15 @@ where
         &mut self,
         layout: TyLayout<'tcx>,
         kind: MemoryKind<M::MemoryKinds>,
-    ) -> EvalResult<'tcx, MPlaceTy<'tcx, M::PointerTag>> {
+    ) -> MPlaceTy<'tcx, M::PointerTag> {
         if layout.is_unsized() {
             assert!(self.tcx.features().unsized_locals, "cannot alloc memory for unsized type");
             // FIXME: What should we do here? We should definitely also tag!
-            Ok(MPlaceTy::dangling(layout, self))
+            MPlaceTy::dangling(layout, self)
         } else {
-            let ptr = self.memory.allocate(layout.size, layout.align.abi, kind)?;
-            let ptr = M::tag_new_allocation(self, ptr, kind)?;
-            Ok(MPlaceTy::from_aligned_ptr(ptr, layout))
+            let ptr = self.memory.allocate(layout.size, layout.align.abi, kind);
+            let ptr = M::tag_new_allocation(self, ptr, kind);
+            MPlaceTy::from_aligned_ptr(ptr, layout)
         }
     }
 

src/librustc_mir/interpret/traits.rs

@@ -54,7 +54,7 @@ impl<'a, 'mir, 'tcx, M: Machine<'a, 'mir, 'tcx>> EvalContext<'a, 'mir, 'tcx, M>
             ptr_size * (3 + methods.len() as u64),
             ptr_align,
             MemoryKind::Vtable,
-        )?.with_default_tag();
+        ).with_default_tag();
         let tcx = &*self.tcx;
 
         let drop = ::monomorphize::resolve_drop_in_place(*tcx, ty);

src/librustc_mir/transform/const_prop.rs

@@ -346,7 +346,7 @@ impl<'a, 'mir, 'tcx> ConstPropagator<'a, 'mir, 'tcx> {
             Rvalue::Cast(kind, ref operand, _) => {
                 let (op, span) = self.eval_operand(operand, source_info)?;
                 self.use_ecx(source_info, |this| {
-                    let dest = this.ecx.allocate(place_layout, MemoryKind::Stack)?;
+                    let dest = this.ecx.allocate(place_layout, MemoryKind::Stack);
                     this.ecx.cast(op, kind, dest.into())?;
                     Ok((dest.into(), span))
                 })