Sanity-check all constants

Author: oli-obk

src/librustc/lib.rs

@@ -73,6 +73,7 @@
 #![feature(in_band_lifetimes)]
 #![feature(macro_at_most_once_rep)]
 #![feature(inclusive_range_methods)]
+#![feature(crate_in_paths)]
 
 #![recursion_limit="512"]
 

src/librustc/mir/interpret/error.rs

@@ -47,7 +47,7 @@ impl<'a, 'gcx, 'tcx> ConstEvalErr<'tcx> {
         tcx: TyCtxtAt<'a, 'gcx, 'tcx>,
         message: &str
     ) {
-        let err = self.struct_generic(tcx, message, None);
+        let err = self.struct_error(tcx, message);
         if let Some(mut err) = err {
             err.emit();
         }

src/librustc/ty/layout.rs

@@ -1599,7 +1599,7 @@ impl<'a, 'tcx, C> TyLayoutMethods<'tcx, C> for Ty<'tcx>
             // Potentially-fat pointers.
             ty::TyRef(_, pointee, _) |
             ty::TyRawPtr(ty::TypeAndMut { ty: pointee, .. }) => {
-                assert!(i < 2);
+                assert!(i < this.fields.count());
 
                 // Reuse the fat *T type as its own thin pointer data field.
                 // This provides information about e.g. DST struct pointees
@@ -1621,10 +1621,25 @@ impl<'a, 'tcx, C> TyLayoutMethods<'tcx, C> for Ty<'tcx>
                 match tcx.struct_tail(pointee).sty {
                     ty::TySlice(_) |
                     ty::TyStr => tcx.types.usize,
-                    ty::TyDynamic(..) => {
-                        // FIXME(eddyb) use an usize/fn() array with
-                        // the correct number of vtables slots.
-                        tcx.mk_imm_ref(tcx.types.re_static, tcx.mk_nil())
+                    ty::TyDynamic(data, _) => {
+                        let trait_def_id = data.principal().unwrap().def_id();
+                        let num_fns: u64 = crate::traits::supertrait_def_ids(tcx, trait_def_id)
+                            .map(|trait_def_id| {
+                                tcx.associated_items(trait_def_id)
+                                    .filter(|item| item.kind == ty::AssociatedKind::Method)
+                                    .count() as u64
+                            })
+                            .sum();
+                        tcx.mk_imm_ref(
+                            tcx.types.re_static,
+                            tcx.mk_array(tcx.types.usize, 3 + num_fns),
+                        )
+                        /* FIXME use actual fn pointers
+                        tcx.mk_tup(&[
+                            tcx.mk_array(tcx.types.usize, 3),
+                            tcx.mk_array(Option<fn()>),
+                        ])
+                        */
                     }
                     _ => bug!("TyLayout::field_type({:?}): not applicable", this)
                 }

src/librustc_lint/builtin.rs

@@ -40,6 +40,7 @@ use lint::{LateContext, LintContext, LintArray};
 use lint::{LintPass, LateLintPass, EarlyLintPass, EarlyContext};
 
 use std::collections::HashSet;
+use rustc::util::nodemap::FxHashSet;
 
 use syntax::tokenstream::{TokenTree, TokenStream};
 use syntax::ast;
@@ -1576,20 +1577,77 @@ impl LintPass for UnusedBrokenConst {
     }
 }
 
+fn validate_const<'a, 'tcx>(
+    tcx: ty::TyCtxt<'a, 'tcx, 'tcx>,
+    constant: &ty::Const<'tcx>,
+    param_env: ty::ParamEnv<'tcx>,
+    gid: ::rustc::mir::interpret::GlobalId<'tcx>,
+    what: &str,
+) {
+    let mut ecx = ::rustc_mir::interpret::mk_eval_cx(tcx, gid.instance, param_env).unwrap();
+    let result = (|| {
+        let val = ecx.const_to_value(constant.val)?;
+        use rustc_target::abi::LayoutOf;
+        let layout = ecx.layout_of(constant.ty)?;
+        let place = ecx.allocate_place_for_value(val, layout, None)?;
+        let ptr = place.to_ptr()?;
+        let mut todo = vec![(ptr, layout.ty, String::new())];
+        let mut seen = FxHashSet();
+        seen.insert((ptr, layout.ty));
+        while let Some((ptr, ty, path)) = todo.pop() {
+            let layout = ecx.layout_of(ty)?;
+            ecx.validate_ptr_target(
+                ptr,
+                layout.align,
+                layout,
+                path,
+                &mut seen,
+                &mut todo,
+            )?;
+        }
+        Ok(())
+    })();
+    if let Err(err) = result {
+        let (trace, span) = ecx.generate_stacktrace(None);
+        let err = ::rustc::mir::interpret::ConstEvalErr {
+            error: err,
+            stacktrace: trace,
+            span,
+        };
+        let err = err.struct_error(
+            tcx.at(span),
+            &format!("this {} likely exhibits undefined behavior", what),
+        );
+        if let Some(mut err) = err {
+            err.note("The rules on what exactly is undefined behavior aren't clear, \
+                so this check might be overzealous. Please open an issue on the rust compiler \
+                repository if you believe it should not be considered undefined behavior",
+            );
+            err.emit();
+        }
+    }
+}
+
 fn check_const(cx: &LateContext, body_id: hir::BodyId, what: &str) {
     let def_id = cx.tcx.hir.body_owner_def_id(body_id);
     let param_env = cx.tcx.param_env(def_id);
     let cid = ::rustc::mir::interpret::GlobalId {
         instance: ty::Instance::mono(cx.tcx, def_id),
         promoted: None
     };
-    if let Err(err) = cx.tcx.const_eval(param_env.and(cid)) {
-        let span = cx.tcx.def_span(def_id);
-        err.report_as_lint(
-            cx.tcx.at(span),
-            &format!("this {} cannot be used", what),
-            cx.current_lint_root(),
-        );
+    match cx.tcx.const_eval(param_env.and(cid)) {
+        Ok(val) => validate_const(cx.tcx, val, param_env, cid, what),
+        Err(err) => {
+            // errors for statics are already reported directly in the query
+            if cx.tcx.is_static(def_id).is_none() {
+                let span = cx.tcx.def_span(def_id);
+                err.report_as_lint(
+                    cx.tcx.at(span),
+                    &format!("this {} cannot be used", what),
+                    cx.current_lint_root(),
+                );
+            }
+        },
     }
 }
 
@@ -1610,6 +1668,9 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnusedBrokenConst {
             hir::ItemKind::Const(_, body_id) => {
                 check_const(cx, body_id, "constant");
             },
+            hir::ItemKind::Static(_, _, body_id) => {
+                check_const(cx, body_id, "static");
+            },
             hir::ItemKind::Ty(ref ty, _) => hir::intravisit::walk_ty(
                 &mut UnusedBrokenConstVisitor(cx),
                 ty

src/librustc_mir/interpret/const_eval.rs

@@ -5,7 +5,7 @@ use rustc::hir;
 use rustc::mir::interpret::{ConstEvalErr};
 use rustc::mir;
 use rustc::ty::{self, TyCtxt, Ty, Instance};
-use rustc::ty::layout::{self, LayoutOf, Primitive};
+use rustc::ty::layout::{self, LayoutOf, Primitive, TyLayout};
 use rustc::ty::subst::Subst;
 
 use syntax::ast::Mutability;
@@ -16,7 +16,7 @@ use rustc::mir::interpret::{
     EvalResult, EvalError, EvalErrorKind, GlobalId,
     Value, Scalar, AllocId, Allocation, ConstValue,
 };
-use super::{Place, EvalContext, StackPopCleanup, ValTy, PlaceExtra, Memory, MemoryKind};
+use super::{Place, EvalContext, StackPopCleanup, ValTy, Memory, MemoryKind};
 
 pub fn mk_borrowck_eval_cx<'a, 'mir, 'tcx>(
     tcx: TyCtxt<'a, 'tcx, 'tcx>,
@@ -63,7 +63,7 @@ pub fn eval_promoted<'a, 'mir, 'tcx>(
     cid: GlobalId<'tcx>,
     mir: &'mir mir::Mir<'tcx>,
     param_env: ty::ParamEnv<'tcx>,
-) -> EvalResult<'tcx, (Value, Scalar, Ty<'tcx>)> {
+) -> EvalResult<'tcx, (Value, Scalar, TyLayout<'tcx>)> {
     ecx.with_fresh_body(|ecx| {
         eval_body_using_ecx(ecx, cid, Some(mir), param_env)
     })
@@ -121,7 +121,7 @@ fn eval_body_and_ecx<'a, 'mir, 'tcx>(
     cid: GlobalId<'tcx>,
     mir: Option<&'mir mir::Mir<'tcx>>,
     param_env: ty::ParamEnv<'tcx>,
-) -> (EvalResult<'tcx, (Value, Scalar, Ty<'tcx>)>, EvalContext<'a, 'mir, 'tcx, CompileTimeEvaluator>) {
+) -> (EvalResult<'tcx, (Value, Scalar, TyLayout<'tcx>)>, EvalContext<'a, 'mir, 'tcx, CompileTimeEvaluator>) {
     debug!("eval_body_and_ecx: {:?}, {:?}", cid, param_env);
     // we start out with the best span we have
     // and try improving it down the road when more information is available
@@ -137,7 +137,7 @@ fn eval_body_using_ecx<'a, 'mir, 'tcx>(
     cid: GlobalId<'tcx>,
     mir: Option<&'mir mir::Mir<'tcx>>,
     param_env: ty::ParamEnv<'tcx>,
-) -> EvalResult<'tcx, (Value, Scalar, Ty<'tcx>)> {
+) -> EvalResult<'tcx, (Value, Scalar, TyLayout<'tcx>)> {
     debug!("eval_body: {:?}, {:?}", cid, param_env);
     let tcx = ecx.tcx.tcx;
     let mut mir = match mir {
@@ -182,7 +182,7 @@ fn eval_body_using_ecx<'a, 'mir, 'tcx>(
         // point at the allocation
         _ => Value::ByRef(ptr, layout.align),
     };
-    Ok((value, ptr, layout.ty))
+    Ok((value, ptr, layout))
 }
 
 #[derive(Debug, Clone, Eq, PartialEq, Hash)]
@@ -434,19 +434,7 @@ pub fn const_val_field<'a, 'tcx>(
         let ty = value.ty;
         let value = ecx.const_to_value(value.val)?;
         let layout = ecx.layout_of(ty)?;
-        let (ptr, align) = match value {
-            Value::ByRef(ptr, align) => (ptr, align),
-            Value::ScalarPair(..) | Value::Scalar(_) => {
-                let ptr = ecx.alloc_ptr(ty)?.into();
-                ecx.write_value_to_ptr(value, ptr, layout.align, ty)?;
-                (ptr, layout.align)
-            },
-        };
-        let place = Place::Ptr {
-            ptr,
-            align,
-            extra: variant.map_or(PlaceExtra::None, PlaceExtra::DowncastVariant),
-        };
+        let place = ecx.allocate_place_for_value(value, layout, variant)?;
         let (place, layout) = ecx.place_field(place, field, layout)?;
         let (ptr, align) = place.to_ptr_align();
         let mut new_value = Value::ByRef(ptr, align);
@@ -484,17 +472,17 @@ pub fn const_variant_index<'a, 'tcx>(
     trace!("const_variant_index: {:?}, {:?}", instance, val);
     let mut ecx = mk_eval_cx(tcx, instance, param_env).unwrap();
     let value = ecx.const_to_value(val.val)?;
+    let layout = ecx.layout_of(val.ty)?;
     let (ptr, align) = match value {
         Value::ScalarPair(..) | Value::Scalar(_) => {
-            let layout = ecx.layout_of(val.ty)?;
             let ptr = ecx.memory.allocate(layout.size, layout.align, MemoryKind::Stack)?.into();
             ecx.write_value_to_ptr(value, ptr, layout.align, val.ty)?;
             (ptr, layout.align)
         },
         Value::ByRef(ptr, align) => (ptr, align),
     };
     let place = Place::from_scalar_ptr(ptr, align);
-    ecx.read_discriminant_as_variant_index(place, val.ty)
+    ecx.read_discriminant_as_variant_index(place, layout)
 }
 
 pub fn const_value_to_allocation_provider<'a, 'tcx>(
@@ -560,11 +548,11 @@ pub fn const_eval_provider<'a, 'tcx>(
     };
 
     let (res, ecx) = eval_body_and_ecx(tcx, cid, None, key.param_env);
-    res.and_then(|(mut val, _, miri_ty)| {
+    res.and_then(|(mut val, _, layout)| {
         if tcx.is_static(def_id).is_none() && cid.promoted.is_none() {
-            val = ecx.try_read_by_ref(val, miri_ty)?;
+            val = ecx.try_read_by_ref(val, layout.ty)?;
         }
-        Ok(value_to_const_value(&ecx, val, miri_ty))
+        Ok(value_to_const_value(&ecx, val, layout.ty))
     }).map_err(|err| {
         let (trace, span) = ecx.generate_stacktrace(None);
         let err = ConstEvalErr {