ICE "anonymous bound region BrAnon(0) in return but not args" #43567

SimonSapin · 2017-07-31T12:39:33Z

rustc 1.21.0-nightly (aac223f 2017-07-30) ICEs on https://github.com/rtbo/rust-xcb (full output below), although 1.20.0-beta.1 and some not-much-older nightlies succeed.

Some more context around the line in the error message:

#[repr(C)]
pub struct xcb_depth_iterator_t<'a> {
    pub data:  *mut xcb_depth_t,
    pub rem:   c_int,
    pub index: c_int,
    _phantom:  std::marker::PhantomData<&'a xcb_depth_t>,
}
// […]
#[link(name="xcb")]
extern {
// […]
    pub fn xcb_screen_allowed_depths_iterator (R: *const xcb_screen_t)
            -> xcb_depth_iterator_t;

So the xcb_depth_iterator_t does have lifetime parameter that’s elided in this function declaration’s return type without any elided lifetime in the parameters. Maybe this code should indeed be rejected, but in that case we need a proper error message rather than a compiler panic. Although it used to be accepted, so this is a breaking change. Adding an explicit lifetime parameter to the function fixes this, but that’s not easy to do properly since this is generated code.

Full output:

% RUST_BACKTRACE=1 cargo +nightly build -v
       Fresh log v0.3.8
       Fresh libc v0.2.28
   Compiling xcb v0.8.0 (file:///home/simon/projects/rust-xcb)
     Running `rustc --crate-name xcb src/lib.rs --crate-type lib --emit=dep-info,link -C debuginfo=2 -C metadata=f22742bf239db509 -C extra-filename=-f22742bf239db509 --out-dir /home/simon/projects/rust-xcb/target/debug/deps -L dependency=/home/simon/projects/rust-xcb/target/debug/deps --extern log=/home/simon/projects/rust-xcb/target/debug/deps/liblog-2b956ee286098ab8.rlib --extern libc=/home/simon/projects/rust-xcb/target/debug/deps/liblibc-c727996240879c34.rlib`
error: internal compiler error: /checkout/src/librustc_typeck/astconv.rs:1267: anonymous bound region BrAnon(0) in return but not args
    --> src/ffi/xproto.rs:5654:16
     |
5654 |             -> xcb_depth_iterator_t;
     |                ^^^^^^^^^^^^^^^^^^^^

note: the compiler unexpectedly panicked. this is a bug.

note: we would appreciate a bug report: https://github.com/rust-lang/rust/blob/master/CONTRIBUTING.md#bug-reports

note: rustc 1.21.0-nightly (aac223f4f 2017-07-30) running on x86_64-unknown-linux-gnu

note: run with `RUST_BACKTRACE=1` for a backtrace

thread 'rustc' panicked at 'Box<Any>', /checkout/src/librustc_errors/lib.rs:438:8
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.
stack backtrace:
   0: std::sys::imp::backtrace::tracing::imp::unwind_backtrace
             at /checkout/src/libstd/sys/unix/backtrace/tracing/gcc_s.rs:49
   1: std::sys_common::backtrace::_print
             at /checkout/src/libstd/sys_common/backtrace.rs:71
   2: std::panicking::default_hook::{{closure}}
             at /checkout/src/libstd/sys_common/backtrace.rs:60
             at /checkout/src/libstd/panicking.rs:380
   3: std::panicking::default_hook
             at /checkout/src/libstd/panicking.rs:390
   4: std::panicking::rust_panic_with_hook
             at /checkout/src/libstd/panicking.rs:610
   5: std::panicking::begin_panic
   6: rustc_errors::Handler::span_bug
   7: rustc::session::opt_span_bug_fmt::{{closure}}
   8: rustc::session::span_bug_fmt
   9: <rustc_typeck::astconv::AstConv<'gcx, 'tcx> + 'o>::ty_of_fn
  10: rustc_typeck::collect::fn_sig
  11: rustc::dep_graph::graph::DepGraph::with_task
  12: rustc::ty::maps::<impl rustc::ty::maps::queries::fn_sig<'tcx>>::try_get
  13: rustc::ty::maps::TyCtxtAt::fn_sig
  14: rustc::ty::maps::<impl rustc::ty::context::TyCtxt<'a, 'tcx, 'lcx>>::fn_sig
  15: <rustc_typeck::collect::CollectItemTypesVisitor<'a, 'tcx> as rustc::hir::intravisit::Visitor<'tcx>>::visit_item
  16: rustc_typeck::check_crate::{{closure}}::{{closure}}
  17: rustc_typeck::check_crate
  18: rustc_driver::driver::phase_3_run_analysis_passes::{{closure}}
  19: rustc_driver::driver::phase_3_run_analysis_passes
  20: rustc_driver::driver::compile_input
  21: rustc_driver::run_compiler

error: Could not compile `xcb`.

Caused by:
  process didn't exit successfully: `rustc --crate-name xcb src/lib.rs --crate-type lib --emit=dep-info,link -C debuginfo=2 -C metadata=f22742bf239db509 -C extra-filename=-f22742bf239db509 --out-dir /home/simon/projects/rust-xcb/target/debug/deps -L dependency=/home/simon/projects/rust-xcb/target/debug/deps --extern log=/home/simon/projects/rust-xcb/target/debug/deps/liblog-2b956ee286098ab8.rlib --extern libc=/home/simon/projects/rust-xcb/target/debug/deps/liblibc-c727996240879c34.rlib` (exit code: 101)

The text was updated successfully, but these errors were encountered:

petrochenkov · 2017-07-31T13:23:41Z

Must be a regression from #43543

Looks like #32330 wasn't fixed in foreign functions :(
I'll prepare a patch.

SimonSapin · 2017-07-31T14:39:13Z

@petrochenkov Do you mean a patch that would make xcb compile, or produce a better error message?

petrochenkov · 2017-07-31T14:56:35Z

@SimonSapin
Don't know yet, need to look closer.
A proper fix may require a warning, deprecation period, etc, but immediate fix for the ICE making xcb compile can always be done by partially reverting #43543.

SimonSapin · 2017-07-31T15:10:29Z

Ok, thanks for looking into it.

Mark-Simulacrum · 2017-08-01T00:39:43Z

Performance collection for the style crate is also broken because of this.

eddyb · 2017-08-01T18:16:37Z

cc @nikomatsakis Should we add elision logic to foreign functions?

Manishearth · 2017-08-01T18:30:48Z

#43594 has a simpler testcase that also involves elision.

Also, yes, I think elision should work on FFI. Firstly, it used to, and it's a breaking change otherwise.

Secondly, this is extremely useful when paired with bindgen to have a modicum of safety wrt returning non-owners pointers from FFI. Dereferenced raw pointers yield values of arbitrary lifetime, and guarding against this in FFI-heavy code is extremely tedious. In an FFI-heavy project the risk of introducing unsafety in the FFI layer can outweigh the risk of just writing it all in C++, largely due to things like this.

eddyb · 2017-08-01T18:32:43Z

@Manishearth Elision never worked, what you were getting was an unbound lifetime in the return.

eddyb · 2017-08-01T18:33:37Z

@Manishearth It was even you who reported #35851. I found two crates that would break so we didn't go through with adding elision to them.

Manishearth · 2017-08-01T18:34:19Z

Wait, what? I could swear we've had lifetime errors on this before. Or perhaps they were in nearby FFI wrappers. Hmm.

Manishearth · 2017-08-01T18:38:15Z

Oh, right, I didn't remember that was all elision.

Opt in would be okay by me too, really. Then again, we also need this on stable.

Can we add elision for the cases where there isn't a function returning a dangling lifetime (and deal with the backcompat hazard separately?). That seems like it can be done a without breaking anyone. As it stands this will break stylo, and it is super nontrivial to fix given the amount of FFI we do.

Manishearth · 2017-08-01T18:40:37Z

I can also try to fix those crates preemptively.

eddyb · 2017-08-01T18:43:15Z

If anyone wants to test with the no-elision-in-FFI hack turned off, change this match arm to => None.

SimonSapin · 2017-08-01T20:04:52Z

I think this is not a case of valid elision. If I add a non-FFI function with the same signature it fails to build with a proper error message because there is no implicit lifetime in the function’s parameters.

    pub fn xcb_screen_allowed_depths_iterator__ (R: *const xcb_screen_t)
            -> xcb_depth_iterator_t { unimplemented!() }

error[E0106]: missing lifetime specifier
 --> src/ffi/xproto.rs:8:16
  |
8 |             -> xcb_depth_iterator_t { unimplemented!() }
  |                ^^^^^^^^^^^^^^^^^^^^ expected lifetime parameter
  |
  = help: this function's return type contains a borrowed value with an elided lifetime, but the lifetime cannot be derived from the arguments
  = help: consider giving it an explicit bounded or 'static lifetime

Manishearth · 2017-08-01T20:24:41Z

FWIW the testcase in #43594 is a case of valid elision, even though it's invalid here.

Manishearth · 2017-08-01T20:39:07Z

Actually, it occurs to me that this bound region bug is going to happen anyway and break all of the crates rely on this anyway, so we should just enable elision for extern fns .. ?

Manishearth · 2017-08-01T20:44:40Z

PR to fix rust-xcb: https://github.com/rtbo/rust-xcb/pull/41

Manishearth · 2017-08-01T21:43:05Z

Fixed liquidfun-rust rjanicek/liquidfun-rust#4

Might be worth a fresh crater run.

eddyb · 2017-08-01T23:01:48Z

cc @Mark-Simulacrum Cargobomb would be helpful.

Mark-Simulacrum · 2017-08-02T04:19:23Z

I don't have access to cargobomb myself, but @tomprince and @brson do, I believe. A patch would be useful either way.

kornelski · 2017-08-05T01:20:18Z

I've ran into the same error. Here's a minimal case:

extern "C" {
    fn ice(ice: &mut u32) -> &u32;
}

error: internal compiler error: src/librustc_typeck/astconv.rs:1267: anonymous bound region BrAnon(1) in return but not args

rustc 1.21.0-nightly (1d2a6df 2017-08-03) running on x86_64-apple-darwin

@eddyb

Fix ICE with elided lifetimes in return type of foreign functions cc #43567 This is for a preliminary crater/cargobomb run. Lifetime elision still produces a late-bound lifetime, but it is caught by the same check as catches `type F = for<'a> fn() -> &'a u8` and reported as an error. If the breakage is significant, I'll have to partially revert #43543 (all the stuff that was required for dealing with late bound lifetimes in this position). r? @eddyb

fixes rust-lang#35851, fixes rust-lang#43567

emilio · 2017-08-08T08:43:59Z

This also happens on Stylo FWIW.

Manishearth · 2017-08-08T08:45:53Z

(we know, see #43594)

Manishearth · 2017-08-08T08:46:28Z

I've fixed up stylo so that the fix for this issue will play nice with it (and the fix for this issue should be in nightly now)

emilio · 2017-08-08T08:52:10Z

It panics on current master with ./mach cargo-geckolib build, so did you forget to update the bindings? Or is it another instance of the problem?

Manishearth · 2017-08-08T14:43:14Z

Compiles for me on latest nightly :)

main-- · 2017-08-08T15:45:33Z

Still failing here: https://travis-ci.org/main--/windows-gaming/jobs/262206955#L1731

SimonSapin · 2017-08-08T15:53:23Z

I’m also still seeing this failure with rustc 1.21.0-nightly (cbbe17a 2017-08-07) (same as @main--) on Servo. @Manishearth, which version did you use, and what did you test?

Manishearth · 2017-08-08T20:10:58Z

Oh, right, I used stable by accident. Oops.

Looks like it never landed on master, only try.

eddyb · 2017-08-09T00:02:38Z

@Manishearth I think @tomprince started the cargobomb run only today.

michaelwoerister · 2017-08-10T20:49:41Z

Discussed in the compiler team meeting. P-high.

petrochenkov · 2017-08-11T13:51:18Z

In the meantime, could someone fix these issues in xcb/stylo/etc by adding explicit lifetimes?
If something ICEs with this message now, there's a good chance it will be an error sooner or later (maybe after deprecation period), so it will need to be fixed anyway.

Manishearth · 2017-08-11T15:45:08Z

It should be fixed in stylo.

I am unable to fix XCB, they use a pretty weird custom bindings generation setup that uses lifetimes but doesn't carry enough info around for those lifetimes to be used consistently. A maintainer of that crate will have to fix it; I'm just not familiar enough with this custom setup to deal with it.

SimonSapin · 2017-08-11T15:49:02Z

(~~I think Stylo was not affected, only Servo.~~ We worked around by forking xcb and modifying manually the generated code. Hopefully this is temporary until someone can figure out a proper fix in the code generation script.)

nox · 2017-08-14T09:39:51Z

This kind of bug is why mozilla-central should never use the system Rust, and always download its own that it knows will work.

@eddyb

Fix ICE with elided lifetimes in return type of foreign functions cc #43567 This is for a preliminary crater/cargobomb run. Lifetime elision in foreign functions now works exactly like in other functions or function-like entities. If the breakage is significant, I'll have to partially revert #43543 (all the stuff that was required for dealing with late bound lifetimes in this position). r? @eddyb

petrochenkov · 2017-08-16T09:49:25Z

Fixed in #43651

SimonSapin · 2017-08-17T14:03:08Z

Confirmed that Firefox compiles on Rust Nightly, with #43651. Thanks!

SimonSapin mentioned this issue Jul 31, 2017

Doesn’t build in recent Nightly, "anonymous bound region BrAnon(0) in return but not args" rust-x-bindings/rust-xcb#40

Closed

Mark-Simulacrum added C-bug Category: This is a bug. I-ICE Issue: The compiler panicked, giving an Internal Compilation Error (ICE) ❄️ T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Aug 1, 2017

alexcrichton added I-nominated regression-from-stable-to-nightly Performance or correctness regression from stable to nightly. labels Aug 1, 2017

Mark-Simulacrum mentioned this issue Aug 1, 2017

error: internal compiler error: src/librustc_typeck/astconv.rs:1267: anonymous bound region BrAnon(1) in return but not args #43594

Closed

Manishearth mentioned this issue Aug 1, 2017

Use more lifetimes rust-x-bindings/rust-xcb#41

Closed

petrochenkov self-assigned this Aug 1, 2017

Mark-Simulacrum mentioned this issue Aug 1, 2017

internal compiler error: anonymous bound region BrAnon(1) in return but not args #43599

Closed

Manishearth mentioned this issue Aug 1, 2017

Upgrade for latest Rust rjanicek/liquidfun-rust#4

Open

gcp mentioned this issue Aug 4, 2017

Nightly is panicking on mozilla-inbound 901c59d3ab9f (stylo) #43638

Closed

petrochenkov mentioned this issue Aug 5, 2017

Fix ICE with elided lifetimes in return type of foreign functions #43651

Merged

Manishearth added a commit to Manishearth/rust that referenced this issue Aug 6, 2017

Add lifetime elision to foreign function declarations

4e8504a

fixes rust-lang#35851, fixes rust-lang#43567

kennytm mentioned this issue Aug 8, 2017

Compiling xcb: internal compiler error: anonymous bound region BrAnon(0) in return but not args #43734

Closed

michaelwoerister added P-high High priority and removed I-nominated labels Aug 10, 2017

Mark-Simulacrum mentioned this issue Aug 11, 2017

Cannot compile firefox anymore #43808

Closed

SimonSapin mentioned this issue Aug 11, 2017

Unfork rust-xcb servo/servo#18044

Closed

petrochenkov closed this as completed Aug 16, 2017

dtolnay mentioned this issue Jan 17, 2018

Anonymous bound region BrAnon(0) in return but not args #47511

Closed

ICE "anonymous bound region BrAnon(0) in return but not args" #43567

ICE "anonymous bound region BrAnon(0) in return but not args" #43567

Comments

SimonSapin commented Jul 31, 2017

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