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add a recursion limit for type representation
I could have added a check for explicit recursion, as irregular types
tend to cause selection errors, but I am not sufficiently sure that
cannot be bypassed.

Fixes #22919
Fixes #25639
Fixes #26548
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arielb1 authored and Ariel Ben-Yehuda committed Oct 27, 2015
1 parent 867fd0a commit 1220e01
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Showing 3 changed files with 44 additions and 0 deletions.
23 changes: 23 additions & 0 deletions src/librustc_trans/trans/context.rs
Expand Up @@ -156,6 +156,9 @@ pub struct LocalCrateContext<'tcx> {
/// contexts around the same size.
n_llvm_insns: Cell<usize>,

/// Depth of the current type-of computation - used to bail out
type_of_depth: Cell<usize>,

trait_cache: RefCell<FnvHashMap<ty::PolyTraitRef<'tcx>,
traits::Vtable<'tcx, ()>>>,
}
Expand Down Expand Up @@ -470,6 +473,7 @@ impl<'tcx> LocalCrateContext<'tcx> {
unwind_resume_hooked: Cell::new(false),
intrinsics: RefCell::new(FnvHashMap()),
n_llvm_insns: Cell::new(0),
type_of_depth: Cell::new(0),
trait_cache: RefCell::new(FnvHashMap()),
};

Expand Down Expand Up @@ -774,6 +778,17 @@ impl<'b, 'tcx> CrateContext<'b, 'tcx> {
obj))
}

pub fn enter_type_of(&self, ty: Ty<'tcx>) -> TypeOfDepthLock<'b, 'tcx> {
let current_depth = self.local.type_of_depth.get();
debug!("enter_type_of({:?}) at depth {:?}", ty, current_depth);
if current_depth > self.sess().recursion_limit.get() {
self.sess().fatal(
&format!("overflow representing the type `{}`", ty))
}
self.local.type_of_depth.set(current_depth + 1);
TypeOfDepthLock(self.local)
}

pub fn check_overflow(&self) -> bool {
self.shared.check_overflow
}
Expand All @@ -790,6 +805,14 @@ impl<'b, 'tcx> CrateContext<'b, 'tcx> {
}
}

pub struct TypeOfDepthLock<'a, 'tcx: 'a>(&'a LocalCrateContext<'tcx>);

impl<'a, 'tcx> Drop for TypeOfDepthLock<'a, 'tcx> {
fn drop(&mut self) {
self.0.type_of_depth.set(self.0.type_of_depth.get() - 1);
}
}

/// Declare any llvm intrinsics that you might need
fn declare_intrinsic(ccx: &CrateContext, key: &str) -> Option<ValueRef> {
macro_rules! ifn {
Expand Down
2 changes: 2 additions & 0 deletions src/librustc_trans/trans/type_of.rs
Expand Up @@ -184,6 +184,8 @@ pub fn sizing_type_of<'a, 'tcx>(cx: &CrateContext<'a, 'tcx>, t: Ty<'tcx>) -> Typ
}

debug!("sizing_type_of {:?}", t);
let _recursion_lock = cx.enter_type_of(t);

let llsizingty = match t.sty {
_ if !type_is_sized(cx.tcx(), t) => {
Type::struct_(cx, &[Type::i8p(cx), Type::i8p(cx)], false)
Expand Down
19 changes: 19 additions & 0 deletions src/test/compile-fail/issue-26548.rs
@@ -0,0 +1,19 @@
// Copyright 2015 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.

// error-pattern: overflow representing the type `S`

trait Mirror { type It; }
impl<T> Mirror for T { type It = Self; }
struct S(Option<<S as Mirror>::It>);

fn main() {
let _s = S(None);
}

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