nalgebra NoSolution Broken MIR ICE #66768
Comments
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Backtrace: |
jonas-schievink
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C-bug
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rustbot
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E-needs-bisection
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The types in the ICE message are: That does look like a missing normalization, but those are not usually so hard to reproduce. |
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@hellow554: I turned off incremental compilation for all my tests. The bug is completely reproducible without incremental compilation. EDIT: See clarification below. |
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@hellow554: sorry, my initial statement was unclear and might be misunderstood. What I meant is that incremental compilation has no influence on the "hard to reproduce" property of the bug. I explicitly turned off incremental compilation for all my debugging, and the weird behavior with e.g. removing dependencies or features still persisted. |
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Especially bizarre is when you substitute "default" for "std" when default only implies "std" in the |
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This issue reminds of #66353 which has been fixed by #66388. Bisection shows regression somewhere between b9de4ef...c6e9c76 but I can't find a commit that would make sense... :/ |
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Probably bisection is going to be difficult since the bug is so hard to reliably reproduce. It would help to reduce it further (removing the |
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Reduced example gives "broken MIR" error on current stable & nightly: #![no_std]
use core::ops::{Add, Mul};
use core::marker::PhantomData;
fn problematic_function<Space>(material_surface_element: Edge2dElement)
where
DefaultAllocator: FiniteElementAllocator<DimU1, Space>,
{
let _: Point2<f64> = material_surface_element.map_reference_coords().into();
}
impl<T> ArrayLength<T> for UTerm {
type ArrayType = ();
}
impl<T, N: ArrayLength<T>> ArrayLength<T> for UInt<N, B0> {
type ArrayType = GenericArrayImplEven<T, N>;
}
impl<T, N: ArrayLength<T>> ArrayLength<T> for UInt<N, B1> {
type ArrayType = GenericArrayImplOdd<T, N>;
}
impl<U> Add<U> for UTerm {
type Output = U;
fn add(self, _: U) -> Self::Output {
unimplemented!()
}
}
impl<Ul, Ur> Add<UInt<Ur, B1>> for UInt<Ul, B0>
where
Ul: Add<Ur>,
{
type Output = UInt<Sum<Ul, Ur>, B1>;
fn add(self, _: UInt<Ur, B1>) -> Self::Output {
unimplemented!()
}
}
impl<U> Mul<U> for UTerm {
type Output = UTerm;
fn mul(self, _: U) -> Self {
unimplemented!()
}
}
impl<Ul, B, Ur> Mul<UInt<Ur, B>> for UInt<Ul, B0>
where
Ul: Mul<UInt<Ur, B>>,
{
type Output = UInt<Prod<Ul, UInt<Ur, B>>, B0>;
fn mul(self, _: UInt<Ur, B>) -> Self::Output {
unimplemented!()
}
}
impl<Ul, B, Ur> Mul<UInt<Ur, B>> for UInt<Ul, B1>
where
Ul: Mul<UInt<Ur, B>>,
UInt<Prod<Ul, UInt<Ur, B>>, B0>: Add<UInt<Ur, B>>,
{
type Output = Sum<UInt<Prod<Ul, UInt<Ur, B>>, B0>, UInt<Ur, B>>;
fn mul(self, _: UInt<Ur, B>) -> Self::Output {
unimplemented!()
}
}
impl<N, R, C> Allocator<N, R, C> for DefaultAllocator
where
R: DimName,
C: DimName,
R::Value: Mul<C::Value>,
Prod<R::Value, C::Value>: ArrayLength<N>,
{
type Buffer = ArrayStorage<N, R, C>;
fn allocate_uninitialized(_: R, _: C) -> Self::Buffer {
unimplemented!()
}
fn allocate_from_iterator<I>(_: R, _: C, _: I) -> Self::Buffer {
unimplemented!()
}
}
impl<N, C> Allocator<N, Dynamic, C> for DefaultAllocator {
type Buffer = VecStorage<N, Dynamic, C>;
fn allocate_uninitialized(_: Dynamic, _: C) -> Self::Buffer {
unimplemented!()
}
fn allocate_from_iterator<I>(_: Dynamic, _: C, _: I) -> Self::Buffer {
unimplemented!()
}
}
impl DimName for DimU1 {
type Value = U1;
fn name() -> Self {
unimplemented!()
}
}
impl DimName for DimU2 {
type Value = U2;
fn name() -> Self {
unimplemented!()
}
}
impl<N, D> From<VectorN<N, D>> for Point<N, D>
where
DefaultAllocator: Allocator<N, D>,
{
fn from(_: VectorN<N, D>) -> Self {
unimplemented!()
}
}
impl<GeometryDim, NodalDim> FiniteElementAllocator<GeometryDim, NodalDim> for DefaultAllocator where
DefaultAllocator: Allocator<f64, GeometryDim> + Allocator<f64, NodalDim>
{
}
impl ReferenceFiniteElement for Edge2dElement {
type NodalDim = DimU1;
}
impl FiniteElement<DimU2> for Edge2dElement {
fn map_reference_coords(&self) -> Vector2<f64> {
unimplemented!()
}
}
type Owned<N, R, C> = <DefaultAllocator as Allocator<N, R, C>>::Buffer;
type MatrixMN<N, R, C> = Matrix<N, R, C, Owned<N, R, C>>;
type VectorN<N, D> = MatrixMN<N, D, DimU1>;
type Vector2<N> = VectorN<N, DimU2>;
type Point2<N> = Point<N, DimU2>;
type U1 = UInt<UTerm, B1>;
type U2 = UInt<UInt<UTerm, B1>, B0>;
type Sum<A, B> = <A as Add<B>>::Output;
type Prod<A, B> = <A as Mul<B>>::Output;
struct GenericArray<T, U: ArrayLength<T>> {
_data: U::ArrayType,
}
struct GenericArrayImplEven<T, U> {
_parent2: U,
_marker: T,
}
struct GenericArrayImplOdd<T, U> {
_parent2: U,
_data: T,
}
struct B0;
struct B1;
struct UTerm;
struct UInt<U, B> {
_marker: PhantomData<(U, B)>,
}
struct DefaultAllocator;
struct Dynamic;
struct DimU1;
struct DimU2;
struct Matrix<N, R, C, S> {
_data: S,
_phantoms: PhantomData<(N, R, C)>,
}
struct ArrayStorage<N, R, C>
where
R: DimName,
C: DimName,
R::Value: Mul<C::Value>,
Prod<R::Value, C::Value>: ArrayLength<N>,
{
_data: GenericArray<N, Prod<R::Value, C::Value>>,
}
struct VecStorage<N, R, C> {
_data: N,
_nrows: R,
_ncols: C,
}
struct Point<N, D>
where
DefaultAllocator: Allocator<N, D>,
{
_coords: VectorN<N, D>,
}
struct Edge2dElement;
trait ArrayLength<T> {
type ArrayType;
}
trait Allocator<Scalar, R, C = DimU1> {
type Buffer;
fn allocate_uninitialized(nrows: R, ncols: C) -> Self::Buffer;
fn allocate_from_iterator<I>(nrows: R, ncols: C, iter: I) -> Self::Buffer;
}
trait DimName {
type Value;
fn name() -> Self;
}
trait FiniteElementAllocator<GeometryDim, NodalDim>:
Allocator<f64, GeometryDim> + Allocator<f64, NodalDim>
{
}
trait ReferenceFiniteElement {
type NodalDim;
}
trait FiniteElement<GeometryDim>: ReferenceFiniteElement
where
DefaultAllocator: FiniteElementAllocator<GeometryDim, Self::NodalDim>,
{
fn map_reference_coords(&self) -> VectorN<f64, GeometryDim>;
} |
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BTW I made extensive use of C-reduce and rust-reduce to get here, which I notice @pnkfelix didn't mention in his blog ;) |
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Did this ever work, by the way? This is tagged "needs-bisect", but that won't help if this isn't a regression... (or maybe the bisection is just to identify whether or not this is a regression?) |
shots fired! (I admit I didn't mention them there, in part because I have little experience using them. I should try using them, and maybe try adding my techniques to rust-reduce.) |
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@WildCryptoFox the discussion you linked talks about the problem going away between nightlies for 2019-11-15 and 2019-11-16. to my eye, that is not an example of this code having worked in the past, but rather makes it an example of an intermittent failure... (I know at that point it may be in the eye of the beholder...) more specifically, when running atop @jethrogb 's reduction, I continue to see an ICE as far back as nightly-2019-01-01. (I'll pull up some older nightlies in a bit... I had cleaned out my |
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The reduced example gives a ICE on nightly-2017-08-31Before that it compiles with nothing but unused-warnings. This should be an exhaustive list of (merge) commits for that nightly: Edit: Going a bit further back, before error on nightly-2017-07-07 |
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I can't get the MVCE to ice on the latest nightly. Can anyone confirm? |
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@fanninpm The playground agrees using @jethrogb 's reduction. (Still fails on stable) @Andlon Status for your project? |
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I cannot reproduce the ICE with https:/Andlon/ice_testcase or #66768 (comment) since 1.44.0, it compiles fine instead. --- a/Cargo.toml
+++ b/Cargo.toml
@@ -4,8 +4,8 @@ version = "0.1.0"
edition = "2018"
[dependencies.nalgebra]
-git = "https:/rustsim/nalgebra.git"
-rev = "31ef5f0ab02c6ecf279867f07cd63e16cece8b75"
+git = "https:/daingun/nalgebra.git"
+branch = "patch-2"
default-features = false
features = ["serde-serialize", "default"]Otherwise, cargo cannot resolve the deps. I'm going to mark this as |
JohnTitor
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the
E-needs-test
that’s not too much effort, here we go: searched nightlies: from nightly-2020-02-01 to nightly-2020-08-05 bisected with cargo-bisect-rustc v0.5.2Host triple: x86_64-pc-windows-msvc cargo bisect-rustc --start 2020-02-01 --with-cargo --access github --regress non-ice |
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Thanks @steffahn! So, this part fixes the issue, I believe: https:/rust-lang/rust/pull/70452/files#diff-53aef089a36a8e2ed07627fc8915fe63R1763 |
JohnTitor
removed
E-needs-bisection
Add regression test for issue-66768 Fixes rust-lang#66768 This is fixed by rust-lang#70452 (in particular, https:/rust-lang/rust/pull/70452/files#diff-53aef089a36a8e2ed07627fc8915fe63R1763) and I'm not sure it's worth to add this test (i.e. the tests in rust-lang#70452 are enough), so r? @eddyb to confirm it.
(Please feel free to make the title more precise)
This issue was first reported as part of #65934, as it was first believed to be similar in nature. Please also see the discussion therein. However, it seems to be sufficiently different as to warrant its own issue.
Here is an example build log
I've created a relatively minimal testcase, and @WildCryptoFox helped me minimize it further. The testcase can be found here: https:/Andlon/ice_testcase . The current
rust-toolchainfile is set tonightly-2019-11-26, but the bug manifests for a number of different version ofnightly(but not all!), as well asbeta, and before minification it was also present onstable.The conditions triggering the ICE seem to be very brittle: Changing features of dependencies or removing unused dependencies might make the ICE vanish. See also @WildCryptoFox's observations in the aforementioned issue #65934.
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