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ICE: index out of bounds: the len is 7 but the index is 7 #63161
Description
I encountered an ICE today. Below you find the backtrace of running cargo test. I ran cargo clean afterwards and the ICE vanished, so it seams to be connected to incremental compilation.
thread 'rustc' panicked at 'index out of bounds: the len is 7 but the index is 7', /rustc/a53f9df32fbb0b5f4382caaad8f1a46f36ea887c/src/libcore/slice/mod.rs:2695:10
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.
stack backtrace:
0: std::sys::unix::backtrace::tracing::imp::unwind_backtrace
at src/libstd/sys/unix/backtrace/tracing/gcc_s.rs:39
1: std::sys_common::backtrace::_print
at src/libstd/sys_common/backtrace.rs:71
2: std::panicking::default_hook::{{closure}}
at src/libstd/sys_common/backtrace.rs:59
at src/libstd/panicking.rs:197
3: std::panicking::default_hook
at src/libstd/panicking.rs:211
4: rustc::util::common::panic_hook
5: std::panicking::rust_panic_with_hook
at src/libstd/panicking.rs:478
6: std::panicking::continue_panic_fmt
at src/libstd/panicking.rs:381
7: rust_begin_unwind
at src/libstd/panicking.rs:308
8: core::panicking::panic_fmt
at src/libcore/panicking.rs:85
9: core::panicking::panic_bounds_check
at src/libcore/panicking.rs:61
10: <rustc::ty::query::on_disk_cache::CacheDecoder as serialize::serialize::SpecializedDecoder<syntax_pos::span_encoding::Span>>::specialized_decode
11: serialize::serialize::Decoder::read_struct
12: serialize::serialize::Decoder::read_seq
13: serialize::serialize::Decoder::read_struct
14: serialize::serialize::Decoder::read_seq
15: <rustc::mir::Mir as serialize::serialize::Decodable>::decode::{{closure}}
16: rustc::ty::query::on_disk_cache::OnDiskCache::try_load_query_result
17: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::get_query
18: rustc_mir::monomorphize::collector::collect_items_rec
19: rustc_mir::monomorphize::collector::collect_items_rec
20: rustc_mir::monomorphize::collector::collect_crate_mono_items::{{closure}}
21: rustc::util::common::time
22: rustc_mir::monomorphize::collector::collect_crate_mono_items
23: rustc::util::common::time
24: rustc_mir::monomorphize::partitioning::collect_and_partition_mono_items
25: rustc::ty::query::__query_compute::collect_and_partition_mono_items
26: rustc::ty::query::<impl rustc::ty::query::config::QueryAccessors for rustc::ty::query::queries::collect_and_partition_mono_items>::compute
27: rustc::dep_graph::graph::DepGraph::with_task_impl
28: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::get_query
29: rustc_codegen_ssa::base::codegen_crate
30: <rustc_codegen_llvm::LlvmCodegenBackend as rustc_codegen_utils::codegen_backend::CodegenBackend>::codegen_crate
31: rustc::util::common::time
32: rustc_interface::passes::start_codegen
33: rustc::ty::context::tls::enter_global
34: rustc_interface::passes::BoxedGlobalCtxt::access::{{closure}}
35: rustc_interface::passes::create_global_ctxt::{{closure}}
36: rustc_interface::passes::BoxedGlobalCtxt::enter
37: rustc_interface::queries::Query<T>::compute
38: rustc_interface::queries::<impl rustc_interface::interface::Compiler>::ongoing_codegen
39: rustc_interface::interface::run_compiler_in_existing_thread_pool
40: std::thread::local::LocalKey<T>::with
41: scoped_tls::ScopedKey<T>::set
42: syntax::with_globals
query stack during panic:
#0 [optimized_mir] processing `metadata::tests::sample_metadata_can_be_deserialized::{{closure}}#0`
#1 [collect_and_partition_mono_items] collect_and_partition_mono_items
end of query stack
error: internal compiler error: unexpected panic
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 1.36.0 (a53f9df32 2019-07-03) running on x86_64-unknown-linux-gnu
note: compiler flags: -C debuginfo=2 -C incremental
note: some of the compiler flags provided by cargo are hidden
If required I can attach the full project including the build directories, as I zipped it after the ICE.
Activity
Centril commentedon Jul 31, 2019
If possible, we would most of all appreciate a reproducer that works on the playground (this will facilitate fixing the bug faster) but if that's not possible a link to the zip would be good also.
jfrimmel commentedon Aug 8, 2019
Sorry, I didn't had enough time for it lately.
Are there any guidelines how to track down such an incremental compilation error? Unfortunately I cannot recall the steps I've done.
I've minimized the code in such a way, that removing any more causes the ICE to vanish. I'll attach this Zip-archive, so somebody else might have a look.
Note, that this is not yet a MCVE.
minimized.zip
hellow554 commentedon Aug 13, 2019
@jfrimmel any luck so far? The code looks good, now you have to recall what you did (rename a variable, changed something from a struct to a trait? Deleted members of a struct? Added functions? Removed them?)
I know it's hard to debug incremental bugs (I encountered two so far). Any chance that you can tell us, what you did between
cargo clean,cargo buildand the secondcargo build?jfrimmel commentedon Aug 13, 2019
Unfortunately no. I tried to recall things, that I've done at this point, but any change I made either also ICEs or compiles fine. I've tried to reproduce this by writing the same code again, but obviously I write it a little bit different now, so I cannot get it to crash.
Are there any tips how to deal with those incremental compilation crashes? Trying to reproduce like I'm doing it now is poking around in the dark.
hellow554 commentedon Aug 13, 2019
As said, it could be anything ^^
Here are some examples I've seen so far in the wild:
#62649 (comment)
#61323 (comment)
#60629 (comment)
#58813 (comment)
#60697
#57692
jfrimmel commentedon Aug 13, 2019
Okay, thanks, I'll have a look at the linked issues 😃
H2CO3 commentedon Aug 17, 2019
Today I encountered the same ICE with "the len is 1077 but the index is 1077".
I was writing and running some integration tests; it involved a serialization format (with Serde). I changed an
[u8]array constant in a test case, then the panic occurred. When I changed it again, the ICE went away, and then I couldn't reproduce it anymore, not even with the value that seems to have caused it in the first place.CreepySkeleton commentedon Aug 23, 2019
We've got the same bug with the len number of 30, not on my machine but on travis-ci (the CI account isn't mine). If you guys know how to do the magic to pull the build artifacts from travis - you're welcome, CI account's owner seems willing to cooperate
2 remaining items
AlbertoGP commentedon Mar 27, 2020
Another one here, looks like the same problem and it also went away for now after
cargo clean.incr-comp: hash span end line/column