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Avoid ICEing miri on layout query cycles #111097

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May 3, 2023
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Avoid ICEing miri on layout query cycles #111097

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3 changes: 3 additions & 0 deletions compiler/rustc_middle/messages.ftl
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Original file line number Diff line number Diff line change
Expand Up @@ -32,6 +32,9 @@ middle_values_too_big =
middle_cannot_be_normalized =
unable to determine layout for `{$ty}` because `{$failure_ty}` cannot be normalized

middle_cycle =
a cycle occurred during layout computation

middle_strict_coherence_needs_negative_coherence =
to use `strict_coherence` on this trait, the `with_negative_coherence` feature must be enabled
.label = due to this attribute
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5 changes: 5 additions & 0 deletions compiler/rustc_middle/src/ty/layout.rs
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Expand Up @@ -210,6 +210,7 @@ pub enum LayoutError<'tcx> {
Unknown(Ty<'tcx>),
SizeOverflow(Ty<'tcx>),
NormalizationFailure(Ty<'tcx>, NormalizationError<'tcx>),
Cycle,
}

impl IntoDiagnostic<'_, !> for LayoutError<'_> {
Expand All @@ -230,6 +231,9 @@ impl IntoDiagnostic<'_, !> for LayoutError<'_> {
diag.set_arg("failure_ty", e.get_type_for_failure());
diag.set_primary_message(fluent::middle_cannot_be_normalized);
}
LayoutError::Cycle => {
diag.set_primary_message(fluent::middle_cycle);
}
}
diag
}
Expand All @@ -250,6 +254,7 @@ impl<'tcx> fmt::Display for LayoutError<'tcx> {
t,
e.get_type_for_failure()
),
LayoutError::Cycle => write!(f, "a cycle occurred during layout computation"),
}
}
}
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6 changes: 6 additions & 0 deletions compiler/rustc_middle/src/values.rs
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Expand Up @@ -106,6 +106,12 @@ impl<'tcx> Value<TyCtxt<'tcx>, DepKind> for ty::EarlyBinder<ty::Binder<'_, ty::F
}
}

impl<'tcx, T> Value<TyCtxt<'tcx>, DepKind> for Result<T, ty::layout::LayoutError<'_>> {
fn from_cycle_error(_tcx: TyCtxt<'tcx>, _cycle: &[QueryInfo<DepKind>]) -> Self {
Err(ty::layout::LayoutError::Cycle)
}
}

// item_and_field_ids should form a cycle where each field contains the
// type in the next element in the list
pub fn recursive_type_error(
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93 changes: 49 additions & 44 deletions src/librustdoc/html/templates/type_layout.html
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@@ -1,53 +1,58 @@
<h2 id="layout" class="small-section-header"> {# #}
<h2 id="layout" class="small-section-header"> {# #}
Layout<a href="#layout" class="anchor">§</a> {# #}
</h2> {# #}
<div class="docblock"> {# #}
{% match type_layout_size %}
{% when Ok(type_layout_size) %}
<div class="warning"> {# #}
<p> {# #}
<strong>Note:</strong> Most layout information is <strong>completely {#+ #}
unstable</strong> and may even differ between compilations. {#+ #}
The only exception is types with certain <code>repr(...)</code> {#+ #}
attributes. Please see the Rust Reference’s {#+ #}
<a href="https://doc.rust-lang.org/reference/type-layout.html">“Type Layout”</a> {#+ #}
chapter for details on type layout guarantees. {# #}
</p> {# #}
</div> {# #}
<p><strong>Size:</strong> {{ type_layout_size|safe }}</p> {# #}
{% if !variants.is_empty() %}
<p> {# #}
<strong>Size for each variant:</strong> {# #}
</p> {# #}
<ul> {# #}
{% for (name, layout_size) in variants %}
<li> {# #}
<code>{{ name }}</code>: {#+ #}
{{ layout_size|safe }}
</li> {# #}
{% endfor %}
</ul> {# #}
{% endif %}
{# This kind of layout error can occur with valid code, e.g. if you try to
get the layout of a generic type such as `Vec<T>`. #}
{% when Ok(type_layout_size) %}
<div class="warning"> {# #}
<p> {# #}
<strong>Note:</strong> Most layout information is <strong>completely {#+ #}
unstable</strong> and may even differ between compilations. {#+ #}
The only exception is types with certain <code>repr(...)</code> {#+ #}
attributes. Please see the Rust Reference’s {#+ #}
<a href="https://doc.rust-lang.org/reference/type-layout.html">“Type Layout”</a> {#+ #}
chapter for details on type layout guarantees. {# #}
</p> {# #}
</div> {# #}
<p><strong>Size:</strong> {{ type_layout_size|safe }}</p> {# #}
{% if !variants.is_empty() %}
<p> {# #}
<strong>Size for each variant:</strong> {# #}
</p> {# #}
<ul> {# #}
{% for (name, layout_size) in variants %}
<li> {# #}
<code>{{ name }}</code>: {#+ #}
{{ layout_size|safe }}
</li> {# #}
{% endfor %}
</ul> {# #}
{% endif %}
{# This kind of layout error can occur with valid code, e.g. if you try to
get the layout of a generic type such as `Vec<T>`. #}
{% when Err(LayoutError::Unknown(_)) %}
<p> {# #}
<strong>Note:</strong> Unable to compute type layout, {#+ #}
possibly due to this type having generic parameters. {#+ #}
Layout can only be computed for concrete, fully-instantiated types. {# #}
</p> {# #}
<p> {# #}
<strong>Note:</strong> Unable to compute type layout, {#+ #}
possibly due to this type having generic parameters. {#+ #}
Layout can only be computed for concrete, fully-instantiated types. {# #}
</p> {# #}
{# This kind of error probably can't happen with valid code, but we don't
want to panic and prevent the docs from building, so we just let the
user know that we couldn't compute the layout. #}
want to panic and prevent the docs from building, so we just let the
user know that we couldn't compute the layout. #}
{% when Err(LayoutError::SizeOverflow(_)) %}
<p> {# #}
<strong>Note:</strong> Encountered an error during type layout; {#+ #}
the type was too big. {# #}
</p> {# #}
<p> {# #}
<strong>Note:</strong> Encountered an error during type layout; {#+ #}
the type was too big. {# #}
</p> {# #}
{% when Err(LayoutError::NormalizationFailure(_, _)) %}
<p> {# #}
<strong>Note:</strong> Encountered an error during type layout; {#+ #}
the type failed to be normalized. {# #}
</p> {# #}
{% endmatch %}
<p> {# #}
<strong>Note:</strong> Encountered an error during type layout; {#+ #}
the type failed to be normalized. {# #}
</p> {# #}
{% when Err(LayoutError::Cycle) %}
<p> {# #}
<strong>Note:</strong> Encountered an error during type layout; {#+ #}
the type's layout depended on the type's layout itself. {# #}
</p> {# #}
{% endmatch %}
</div> {# #}
28 changes: 28 additions & 0 deletions src/tools/miri/tests/fail/layout_cycle.rs
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@@ -0,0 +1,28 @@
//@error-pattern: a cycle occurred during layout computation
//~^ ERROR: cycle detected when computing layout of

use std::mem;

pub struct S<T: Tr> {
pub f: <T as Tr>::I,
}

pub trait Tr {
type I: Tr;
}

impl<T: Tr> Tr for S<T> {
type I = S<S<T>>;
}

impl Tr for () {
type I = ();
}

fn foo<T: Tr>() -> usize {
mem::size_of::<S<T>>()
}

fn main() {
println!("{}", foo::<S<()>>());
}
28 changes: 28 additions & 0 deletions src/tools/miri/tests/fail/layout_cycle.stderr
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@@ -0,0 +1,28 @@
error[E0391]: cycle detected when computing layout of `S<S<()>>`
|
= note: ...which requires computing layout of `<S<()> as Tr>::I`...
= note: ...which again requires computing layout of `S<S<()>>`, completing the cycle

error: post-monomorphization error: a cycle occurred during layout computation
--> RUSTLIB/core/src/mem/mod.rs:LL:CC
|
LL | intrinsics::size_of::<T>()
| ^^^^^^^^^^^^^^^^^^^^^^^^^^ a cycle occurred during layout computation
|
= note: inside `std::mem::size_of::<S<S<()>>>` at RUSTLIB/core/src/mem/mod.rs:LL:CC
note: inside `foo::<S<()>>`
--> $DIR/layout_cycle.rs:LL:CC
|
LL | mem::size_of::<S<T>>()
| ^^^^^^^^^^^^^^^^^^^^^^
note: inside `main`
--> $DIR/layout_cycle.rs:LL:CC
|
LL | println!("{}", foo::<S<()>>());
| ^^^^^^^^^^^^^^

note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace

error: aborting due to 2 previous errors

For more information about this error, try `rustc --explain E0391`.