Infinite recursion in rustdoc

[SimonSapin]

When running rustdoc on Servo’s style crate, it currently exists with task '<unknown>' has overflowed its stack. Running it in gdb, the stack trace repeats these four lines a large number of times:

#100 0x00007ffff793300d in visit_ast::RustdocVisitor$LT$$x27a$GT$::visit_item::h868ff071f9f54492HFr ()
   from /home/simon/tmp/servo-build/x86_64-unknown-linux-gnu/rust_snapshot/rust-0.12.0-pre-x86_64-unknown-linux-gnu/lib/librustdoc-4e7c5e5c.so
#101 0x00007ffff793802d in visit_ast::RustdocVisitor$LT$$x27a$GT$::resolve_id::hbba5c6cb8d56390bDCr ()
   from /home/simon/tmp/servo-build/x86_64-unknown-linux-gnu/rust_snapshot/rust-0.12.0-pre-x86_64-unknown-linux-gnu/lib/librustdoc-4e7c5e5c.so
#102 0x00007ffff7931316 in visit_ast::RustdocVisitor$LT$$x27a$GT$::visit_view_item::h500efb8576c4bd72Cyr ()
   from /home/simon/tmp/servo-build/x86_64-unknown-linux-gnu/rust_snapshot/rust-0.12.0-pre-x86_64-unknown-linux-gnu/lib/librustdoc-4e7c5e5c.so
#103 0x00007ffff792c960 in visit_ast::RustdocVisitor$LT$$x27a$GT$::visit_mod_contents::hfd92063fb62d99ackwr ()
   from /home/simon/tmp/servo-build/x86_64-unknown-linux-gnu/rust_snapshot/rust-0.12.0-pre-x86_64-unknown-linux-gnu/lib/librustdoc-4e7c5e5c.so

Running it with RUST_LOG=rustdoc::visit_ast after adding debug!() lines in visit_mod_contents() and resolve_id(), this is a repeating pattern in the output after piping it through cut -d'"' -f 1-2

DEBUG:rustdoc::visit_ast: Visiting item Item { ident: "longhands
DEBUG:rustdoc::visit_ast: Visiting module Some("longhands
DEBUG:rustdoc::visit_ast: Resolve ID: 10021
DEBUG:rustdoc::visit_ast: Resolve ID: 8287
DEBUG:rustdoc::visit_ast: Resolve ID: 8295
DEBUG:rustdoc::visit_ast: Resolve ID: 8296
DEBUG:rustdoc::visit_ast: Resolve ID: 8297
DEBUG:rustdoc::visit_ast: Resolve ID: 8298
DEBUG:rustdoc::visit_ast: Resolve ID: 8302
DEBUG:rustdoc::visit_ast: Visiting item Item { ident: "one_component_value
DEBUG:rustdoc::visit_ast: Visiting fn
DEBUG:rustdoc::visit_ast: Visiting item Item { ident: "get_ident_lower
DEBUG:rustdoc::visit_ast: Visiting fn
DEBUG:rustdoc::visit_ast: Resolve ID: 8303
DEBUG:rustdoc::visit_ast: Resolve ID: 8311
DEBUG:rustdoc::visit_ast: Visiting item Item { ident: "CSSFloat
DEBUG:rustdoc::visit_ast: Visiting item Item { ident: "DEFAULT_LINE_HEIGHT
DEBUG:rustdoc::visit_ast: Visiting item Item { ident: "specified
DEBUG:rustdoc::visit_ast: Visiting module Some("specified
DEBUG:rustdoc::visit_ast: Resolve ID: 8327
DEBUG:rustdoc::visit_ast: Visiting item Item { ident: "Length
DEBUG:rustdoc::visit_ast: Visiting enum
DEBUG:rustdoc::visit_ast: Visiting item Item { ident: "Length.::std::clone::Clone
DEBUG:rustdoc::visit_ast: Visiting item Item { ident: "AU_PER_PX
DEBUG:rustdoc::visit_ast: Visiting item Item { ident: "AU_PER_IN
DEBUG:rustdoc::visit_ast: Visiting item Item { ident: "AU_PER_CM
DEBUG:rustdoc::visit_ast: Visiting item Item { ident: "AU_PER_MM
DEBUG:rustdoc::visit_ast: Visiting item Item { ident: "AU_PER_PT
DEBUG:rustdoc::visit_ast: Visiting item Item { ident: "AU_PER_PC
DEBUG:rustdoc::visit_ast: Visiting item Item { ident: "Length
DEBUG:rustdoc::visit_ast: Visiting item Item { ident: "LengthOrPercentage
DEBUG:rustdoc::visit_ast: Visiting enum
DEBUG:rustdoc::visit_ast: Visiting item Item { ident: "LengthOrPercentage.::std::clone::Clone
DEBUG:rustdoc::visit_ast: Visiting item Item { ident: "LengthOrPercentage
DEBUG:rustdoc::visit_ast: Visiting item Item { ident: "LengthOrPercentageOrAuto
DEBUG:rustdoc::visit_ast: Visiting enum
DEBUG:rustdoc::visit_ast: Visiting item Item { ident: "LengthOrPercentageOrAuto.::std::clone::Clone
DEBUG:rustdoc::visit_ast: Visiting item Item { ident: "LengthOrPercentageOrAuto
DEBUG:rustdoc::visit_ast: Visiting item Item { ident: "LengthOrPercentageOrNone
DEBUG:rustdoc::visit_ast: Visiting enum
DEBUG:rustdoc::visit_ast: Visiting item Item { ident: "LengthOrPercentageOrNone.::std::clone::Clone
DEBUG:rustdoc::visit_ast: Visiting item Item { ident: "LengthOrPercentageOrNone
DEBUG:rustdoc::visit_ast: Visiting item Item { ident: "computed
DEBUG:rustdoc::visit_ast: Visiting module Some("computed
DEBUG:rustdoc::visit_ast: Resolve ID: 9115
DEBUG:rustdoc::visit_ast: Resolve ID: 9116
DEBUG:rustdoc::visit_ast: Visiting item Item { ident: "computed_as_specified
DEBUG:rustdoc::visit_ast: Visiting fn
DEBUG:rustdoc::visit_ast: Resolve ID: 9119
DEBUG:rustdoc::visit_ast: Visiting item Item { ident: "Context
DEBUG:rustdoc::visit_ast: Visiting struct
DEBUG:rustdoc::visit_ast: Visiting item Item { ident: "compute_Au
DEBUG:rustdoc::visit_ast: Visiting fn
DEBUG:rustdoc::visit_ast: Visiting item Item { ident: "compute_Au_with_font_size
DEBUG:rustdoc::visit_ast: Visiting fn
DEBUG:rustdoc::visit_ast: Visiting item Item { ident: "LengthOrPercentage
DEBUG:rustdoc::visit_ast: Visiting enum
DEBUG:rustdoc::visit_ast: Visiting item Item { ident: "LengthOrPercentage.::std::clone::Clone
DEBUG:rustdoc::visit_ast: Visiting item Item { ident: "LengthOrPercentage.::std::cmp::PartialEq
DEBUG:rustdoc::visit_ast: Visiting item Item { ident: "compute_LengthOrPercentage
DEBUG:rustdoc::visit_ast: Visiting fn
DEBUG:rustdoc::visit_ast: Visiting item Item { ident: "LengthOrPercentageOrAuto
DEBUG:rustdoc::visit_ast: Visiting enum
DEBUG:rustdoc::visit_ast: Visiting item Item { ident: "LengthOrPercentageOrAuto.::std::clone::Clone
DEBUG:rustdoc::visit_ast: Visiting item Item { ident: "LengthOrPercentageOrAuto.::std::cmp::PartialEq
DEBUG:rustdoc::visit_ast: Visiting item Item { ident: "compute_LengthOrPercentageOrAuto
DEBUG:rustdoc::visit_ast: Visiting fn
DEBUG:rustdoc::visit_ast: Visiting item Item { ident: "LengthOrPercentageOrNone
DEBUG:rustdoc::visit_ast: Visiting enum
DEBUG:rustdoc::visit_ast: Visiting item Item { ident: "LengthOrPercentageOrNone.::std::clone::Clone
DEBUG:rustdoc::visit_ast: Visiting item Item { ident: "LengthOrPercentageOrNone.::std::cmp::PartialEq
DEBUG:rustdoc::visit_ast: Visiting item Item { ident: "compute_LengthOrPercentageOrNone
DEBUG:rustdoc::visit_ast: Visiting fn
DEBUG:rustdoc::visit_ast: Visiting item Item { ident: "parse_url
DEBUG:rustdoc::visit_ast: Visiting fn
DEBUG:rustdoc::visit_ast: Resolve ID: 8305
DEBUG:rustdoc::visit_ast: Visiting item Item { ident: "PropertyBitField
DEBUG:rustdoc::visit_ast: Visiting struct
DEBUG:rustdoc::visit_ast: Visiting item Item { ident: "common_types
DEBUG:rustdoc::visit_ast: Visiting module Some("common_types
DEBUG:rustdoc::visit_ast: Resolve ID: 8311
DEBUG:rustdoc::visit_ast: Visiting item Item { ident: "CSSFloat
DEBUG:rustdoc::visit_ast: Visiting item Item { ident: "DEFAULT_LINE_HEIGHT
DEBUG:rustdoc::visit_ast: Visiting item Item { ident: "specified
DEBUG:rustdoc::visit_ast: Visiting module Some("specified
DEBUG:rustdoc::visit_ast: Resolve ID: 8327
DEBUG:rustdoc::visit_ast: Visiting item Item { ident: "Length
DEBUG:rustdoc::visit_ast: Visiting enum
DEBUG:rustdoc::visit_ast: Visiting item Item { ident: "Length.::std::clone::Clone
DEBUG:rustdoc::visit_ast: Visiting item Item { ident: "AU_PER_PX
DEBUG:rustdoc::visit_ast: Visiting item Item { ident: "AU_PER_IN
DEBUG:rustdoc::visit_ast: Visiting item Item { ident: "AU_PER_CM
DEBUG:rustdoc::visit_ast: Visiting item Item { ident: "AU_PER_MM
DEBUG:rustdoc::visit_ast: Visiting item Item { ident: "AU_PER_PT
DEBUG:rustdoc::visit_ast: Visiting item Item { ident: "AU_PER_PC
DEBUG:rustdoc::visit_ast: Visiting item Item { ident: "Length
DEBUG:rustdoc::visit_ast: Visiting item Item { ident: "LengthOrPercentage
DEBUG:rustdoc::visit_ast: Visiting enum
DEBUG:rustdoc::visit_ast: Visiting item Item { ident: "LengthOrPercentage.::std::clone::Clone
DEBUG:rustdoc::visit_ast: Visiting item Item { ident: "LengthOrPercentage
DEBUG:rustdoc::visit_ast: Visiting item Item { ident: "LengthOrPercentageOrAuto
DEBUG:rustdoc::visit_ast: Visiting enum
DEBUG:rustdoc::visit_ast: Visiting item Item { ident: "LengthOrPercentageOrAuto.::std::clone::Clone
DEBUG:rustdoc::visit_ast: Visiting item Item { ident: "LengthOrPercentageOrAuto
DEBUG:rustdoc::visit_ast: Visiting item Item { ident: "LengthOrPercentageOrNone
DEBUG:rustdoc::visit_ast: Visiting enum
DEBUG:rustdoc::visit_ast: Visiting item Item { ident: "LengthOrPercentageOrNone.::std::clone::Clone
DEBUG:rustdoc::visit_ast: Visiting item Item { ident: "LengthOrPercentageOrNone
DEBUG:rustdoc::visit_ast: Visiting item Item { ident: "computed
DEBUG:rustdoc::visit_ast: Visiting module Some("computed
DEBUG:rustdoc::visit_ast: Resolve ID: 9115
DEBUG:rustdoc::visit_ast: Resolve ID: 9116
DEBUG:rustdoc::visit_ast: Visiting item Item { ident: "computed_as_specified
DEBUG:rustdoc::visit_ast: Visiting fn
DEBUG:rustdoc::visit_ast: Resolve ID: 9119
DEBUG:rustdoc::visit_ast: Visiting item Item { ident: "Context
DEBUG:rustdoc::visit_ast: Visiting struct
DEBUG:rustdoc::visit_ast: Visiting item Item { ident: "compute_Au
DEBUG:rustdoc::visit_ast: Visiting fn
DEBUG:rustdoc::visit_ast: Visiting item Item { ident: "compute_Au_with_font_size
DEBUG:rustdoc::visit_ast: Visiting fn
DEBUG:rustdoc::visit_ast: Visiting item Item { ident: "LengthOrPercentage
DEBUG:rustdoc::visit_ast: Visiting enum
DEBUG:rustdoc::visit_ast: Visiting item Item { ident: "LengthOrPercentage.::std::clone::Clone
DEBUG:rustdoc::visit_ast: Visiting item Item { ident: "LengthOrPercentage.::std::cmp::PartialEq
DEBUG:rustdoc::visit_ast: Visiting item Item { ident: "compute_LengthOrPercentage
DEBUG:rustdoc::visit_ast: Visiting fn
DEBUG:rustdoc::visit_ast: Visiting item Item { ident: "LengthOrPercentageOrAuto
DEBUG:rustdoc::visit_ast: Visiting enum
DEBUG:rustdoc::visit_ast: Visiting item Item { ident: "LengthOrPercentageOrAuto.::std::clone::Clone
DEBUG:rustdoc::visit_ast: Visiting item Item { ident: "LengthOrPercentageOrAuto.::std::cmp::PartialEq
DEBUG:rustdoc::visit_ast: Visiting item Item { ident: "compute_LengthOrPercentageOrAuto
DEBUG:rustdoc::visit_ast: Visiting fn
DEBUG:rustdoc::visit_ast: Visiting item Item { ident: "LengthOrPercentageOrNone
DEBUG:rustdoc::visit_ast: Visiting enum
DEBUG:rustdoc::visit_ast: Visiting item Item { ident: "LengthOrPercentageOrNone.::std::clone::Clone
DEBUG:rustdoc::visit_ast: Visiting item Item { ident: "LengthOrPercentageOrNone.::std::cmp::PartialEq
DEBUG:rustdoc::visit_ast: Visiting item Item { ident: "compute_LengthOrPercentageOrNone
DEBUG:rustdoc::visit_ast: Visiting fn
DEBUG:rustdoc::visit_ast: Visiting item Item { ident: "parse_url
DEBUG:rustdoc::visit_ast: Visiting fn

I don’t know how to go from here. I don’t really understand what’s going on in the above log.

CC: @eddyb

[SimonSapin]

Steps to reproduce:

• Build Servo
• Remove style from DOC_BLACKLISTED near the beginning of mk/doc.mk
• Run make doc-style

I don’t have a smaller test case yet, sorry.

[pczarn]

This part is very suspicious:

// servo / src / components / style / properties / common_types.rs
pub mod computed {
    //...
    use super::*;
    //...
}

in https://github.com/servo/servo/blob/3670ee6f1fc5066101cc5a357443494552ea37f2/src/components/style/properties/common_types.rs#L165-L170

[SimonSapin]

I even have this:

pub mod longhands {
    pub use super::*;
    pub mod ${property.ident} {
        use super::*;
        // ...

(… which rustc is perfectly happy with, for what it’s worth.)

[pczarn]

This circular reexport is worse:

#![feature(globs)]

pub mod longhands {
    pub use super::*;

    pub use to_computed_value = super::common_types::computed::compute_CSSColor;

    pub fn computed_as_specified() {}
}

pub mod common_types {
    pub mod computed {
        pub use compute_CSSColor = super::super::longhands::computed_as_specified;
    }
}

My rustdoc is not happy: task '<unnamed>' failed at 'couldn't find node id 0 in the AST map', /build/rust-git/src/rust/src/libsyntax/ast_map/mod.rs:220

edit: one more reexport

[SSheldon]

I've encountered the not-infinite-recursion form mentioned above; here's a simple case to repro:

#![crate_type = "lib"]
#![feature(globs)]

pub use a::Foo;

mod a {
    pub struct Foo;
}

mod b {
    pub use super::*;
}

rustdoc prints out:

task '<unnamed>' failed at 'couldn't find node id 0 in the AST map', /Users/rustbuild/src/rust-buildbot/slave/nightly-mac/build/src/libsyntax/ast_map/mod.rs:225
task '<unnamed>' failed at 'called `Result::unwrap()` on an `Err` value: Box<core::any::Any:Send>', /Users/rustbuild/src/rust-buildbot/slave/nightly-mac/build/src/libcore/result.rs:548

If you replace the super glob with pub use super::Foo; there's no error.

[SSheldon]

A smaller test case to reproduce the infinite recursion is:

#![crate_type = "lib"]
#![feature(globs)]

mod m {
    pub use self::a::Foo;

    mod a {
        pub struct Foo;
    }

    mod b {
        pub use super::*;
    }
}

rustdoc prints out:

task '<unknown>' has overflowed its stack
Illegal instruction: 4

Interestingly, if you make pub mod m there's no more infinite recursion.