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Fix stack overflow when generating debuginfo for 'recursive' type #59446

Merged
merged 6 commits into from
Apr 2, 2019
Merged

Fix stack overflow when generating debuginfo for 'recursive' type #59446

merged 6 commits into from
Apr 2, 2019

Commits on Apr 1, 2019

  1. Fix stack overflow when generating debuginfo for 'recursive' type 

    By using 'impl trait', it's possible to create a self-referential
type as follows:

fn foo() -> impl Copy { foo }

This is a function which returns itself.
Normally, the signature of this function would be impossible
to write - it would look like 'fn foo() -> fn() -> fn() ...'
e.g. a function which returns a function, which returns a function...

Using 'impl trait' allows us to avoid writing this infinitely long
type. While it's useless for practical purposes, it does compile and run

However, issues arise when we try to generate llvm debuginfo for such a
type. All 'impl trait' types (e.g. ty::Opaque) are resolved when we
generate debuginfo, which can lead to us recursing back to the original
'fn' type when we try to process its return type.

To resolve this, I've modified debuginfo generation to account for these
kinds of weird types. Unfortunately, there's no 'correct' debuginfo that
we can generate - 'impl trait' does not exist in debuginfo, and this
kind of recursive type is impossible to directly represent.

To ensure that we emit *something*, this commit emits dummy
debuginfo/type names whenever it encounters a self-reference. In
practice, this should never happen - it's just to ensure that we can
emit some kind of debuginfo, even if it's not particularly meaningful

Fixes rust-lang#58463
    @Aaron1011
    Aaron1011 committed Apr 1, 2019
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  2. Fix inverted panic check

    @Aaron1011
    Aaron1011 committed Apr 1, 2019
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  3. Add codegen test

    @Aaron1011
    Aaron1011 committed Apr 1, 2019
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  4. Fix typos

    @Aaron1011
    Aaron1011 committed Apr 1, 2019
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  5. Only track 'visited' state for function types

    @Aaron1011
    Aaron1011 committed Apr 1, 2019
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  6. Fix typo

    @Aaron1011
    Aaron1011 authored Apr 1, 2019
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