"called `Result::unwrap()` on an `Err` value: Utf8Error { valid_up_to: 2 }" ICE in stable

[netvl]

I suddenly got the following error when compiling my crate:

% RUST_BACKTRACE=1 rustup run stable cargo build --verbose
       Fresh num-traits v0.1.32
       Fresh byteorder v0.5.1
       Fresh odds v0.2.12
       Fresh nodrop v0.1.6
       Fresh arrayvec v0.3.15
   Compiling immeta v0.3.4 (file:///home/netvl/dev/lang/rust/projects/immeta)
     Running `rustc src/lib.rs --crate-name immeta --crate-type lib -g --out-dir /home/netvl/dev/lang/rust/projects/immeta/target/debug --emit=dep-info,link -L dependency=/home/netvl/dev/lang/rust/projects/immeta/target/debug -L dependency=/home/netvl/dev/lang/rust/projects/immeta/target/debug/deps --extern arrayvec=/home/netvl/dev/lang/rust/projects/immeta/target/debug/deps/libarrayvec-bcf06b3ef065493b.rlib --extern num_traits=/home/netvl/dev/lang/rust/projects/immeta/target/debug/deps/libnum_traits-a4000e09af4c8117.rlib --extern byteorder=/home/netvl/dev/lang/rust/projects/immeta/target/debug/deps/libbyteorder-4e8da61ace56de4d.rlib`
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
thread 'rustc' panicked at 'called `Result::unwrap()` on an `Err` value: Utf8Error { valid_up_to: 2 }', ../src/libcore/result.rs:746
stack backtrace:
   1:     0x7fa66f6de330 - sys::backtrace::tracing::imp::write::h3675b4f0ca767761Xcv
   2:     0x7fa66f6e768b - panicking::default_handler::_$u7b$$u7b$closure$u7d$$u7d$::closure.44519
   3:     0x7fa66f6e71e3 - panicking::default_handler::h18faf4fbd296d909lSz
   4:     0x7fa66f6ab9ac - sys_common::unwind::begin_unwind_inner::hfb5d07d6e405c6bbg1t
   5:     0x7fa66f6ac448 - sys_common::unwind::begin_unwind_fmt::h8b491a76ae84af35m0t
   6:     0x7fa66f6dbd91 - rust_begin_unwind
   7:     0x7fa66f72e7af - panicking::panic_fmt::h98b8cbb286f5298alcM
   8:     0x7fa6674b731b - result::unwrap_failed::h14307315525592478485
   9:     0x7fa6674b728e - Doc<'doc>::as_str_slice::ha91bf39a19faeabdHVa
  10:     0x7fa66d35f45f - loader::Context<'a>::extract_one::h945c702fbde346e3Eem
  11:     0x7fa66d356acf - loader::Context<'a>::find_library_crate::h30971509c344ad3bD3l
  12:     0x7fa66d33bf16 - loader::Context<'a>::load_library_crate::h0ade06e110892b81WSl
  13:     0x7fa66d33ad99 - creader::CrateReader<'a>::resolve_crate::he1542772b02d0896E3j
  14:     0x7fa66d33c58d - creader::CrateReader<'a>::resolve_crate_deps::_$u7b$$u7b$closure$u7d$$u7d$::closure.38792
  15:     0x7fa66d33c33c - collections::hash::map::HashMap<K, V, S>.FromIterator<(K, V)>::from_iter::h12379182329167058746
  16:     0x7fa66d3384dd - creader::CrateReader<'a>::register_crate::h62645edecf14372cTZj
  17:     0x7fa66d33b6e2 - creader::CrateReader<'a>::resolve_crate::he1542772b02d0896E3j
  18:     0x7fa66d33586b - creader::LocalCrateReader<'a, 'b>.Visitor<'hir>::visit_item::hd760834db1c6f482eDj
  19:     0x7fa66d347d7e - creader::LocalCrateReader<'a, 'b>::read_crates::hb36235539ae0e4e04vk
  20:     0x7fa66fc027c7 - driver::phase_3_run_analysis_passes::h10920926650053012691
  21:     0x7fa66fbd8a15 - driver::compile_input::h7ae6a86e23de0774Hca
  22:     0x7fa66fbc7b47 - run_compiler::hb0408bcf47642fe6mPc
  23:     0x7fa66fbc52c1 - sys_common::unwind::try::try_fn::h7614151098073783683
  24:     0x7fa66f6dbd1b - __rust_try
  25:     0x7fa66f6d41fd - sys_common::unwind::inner_try::hadd81c754a64f07ciYt
  26:     0x7fa66fbc5b10 - boxed::F.FnBox<A>::call_box::h18261575856772421581
  27:     0x7fa66f6e5c59 - sys::thread::Thread::new::thread_start::h9bc812305b5e01feFPy
  28:     0x7fa6689af473 - start_thread
  29:     0x7fa66f35d69c - clone
  30:                0x0 - <unknown>

Could not compile `immeta`.

Caused by:
  Process didn't exit successfully: `rustc src/lib.rs --crate-name immeta --crate-type lib -g --out-dir /home/netvl/dev/lang/rust/projects/immeta/target/debug --emit=dep-info,link -L dependency=/home/netvl/dev/lang/rust/projects/immeta/target/debug -L dependency=/home/netvl/dev/lang/rust/projects/immeta/target/debug/deps --extern arrayvec=/home/netvl/dev/lang/rust/projects/immeta/target/debug/deps/libarrayvec-bcf06b3ef065493b.rlib --extern num_traits=/home/netvl/dev/lang/rust/projects/immeta/target/debug/deps/libnum_traits-a4000e09af4c8117.rlib --extern byteorder=/home/netvl/dev/lang/rust/projects/immeta/target/debug/deps/libbyteorder-4e8da61ace56de4d.rlib` (exit code: 101)

Here are the crate sources: immeta.zip

Apparently there is no such error on travis, so I think this may be caused by some weird interaction of rustc with rustup, but I don't know for sure.

rustc version:

% rustup run stable rustc -Vv
rustc 1.8.0 (db2939409 2016-04-11)
binary: rustc
commit-hash: db2939409db26ab4904372c82492cd3488e4c44e
commit-date: 2016-04-11
host: x86_64-unknown-linux-gnu
release: 1.8.0

cargo version:

% rustup run stable cargo --version
cargo 0.9.0-nightly (8fc3fd8 2016-02-29)

rustup version:

% rustup --version
rustup 0.1.12 (c6e430a 2016-05-12)

[Diggsey]

@netvl Try doing a cargo clean, and then rebuilding. It looks like it might be trying to read the metadata from a crate compiled with a previous version of the compiler.

[mattico]

@Diggsey Can (probably) confirm. I got this same error when switching from nightly-msvc to stable-gnu after aborting a build.

[mkollaro]

Same here. I'm not sure what caused it, but I was switching around between nightly and stable before. Works in nightly, fails in stable. Once it started happening, it was happening every time. Running cargo clean fixed it.

RUST_BACKTRACE=1 cargo build --verbose
       Fresh log v0.3.6
       Fresh libc v0.2.9
       Fresh cfg-if v0.1.0
       Fresh semver v0.1.20
       Fresh getopts v0.2.14
       Fresh bitflags v0.4.0
       Fresh rustc_version v0.1.7
       Fresh nix v0.5.1-pre (https://github.com/mkollaro/nix#22ae34a7)
   Compiling librdb v0.1.0 (file:///mnt/data/src/rdb)
     Running `rustc src/lib.rs --crate-name librdb --crate-type lib -g --cfg feature=\"default\" --out-dir /mnt/data/src/rdb/target/debug --emit=dep-info,link -L dependency=/mnt/data/src/rdb/target/debug -L dependency=/mnt/data/src/rdb/target/debug/deps --extern libc=/mnt/data/src/rdb/target/debug/deps/liblibc-d2268fc21ed63f2c.rlib --extern log=/mnt/data/src/rdb/target/debug/deps/liblog-30a8a27ec161f1be.rlib --extern nix=/mnt/data/src/rdb/target/debug/deps/libnix-4281f0d4c5a4bab6.rlib --extern getopts=/mnt/data/src/rdb/target/debug/deps/libgetopts-852fe11dd444cf81.rlib -L native=/mnt/data/src/rdb/thirdparty/libdwarf/libdwarf -l static=dwarf -l elf -l z`
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
thread 'rustc' panicked at 'called `Result::unwrap()` on an `Err` value: Utf8Error { valid_up_to: 0 }', ../src/libcore/result.rs:746
stack backtrace:
   1:     0x7f96765bc330 - sys::backtrace::tracing::imp::write::h3675b4f0ca767761Xcv
   2:     0x7f96765c568b - panicking::default_handler::_$u7b$$u7b$closure$u7d$$u7d$::closure.44519
   3:     0x7f96765c51e3 - panicking::default_handler::h18faf4fbd296d909lSz
   4:     0x7f96765899ac - sys_common::unwind::begin_unwind_inner::hfb5d07d6e405c6bbg1t
   5:     0x7f967658a448 - sys_common::unwind::begin_unwind_fmt::h8b491a76ae84af35m0t
   6:     0x7f96765b9d91 - rust_begin_unwind
   7:     0x7f967660c7af - panicking::panic_fmt::h98b8cbb286f5298alcM
   8:     0x7f966e36e31b - result::unwrap_failed::h14307315525592478485
   9:     0x7f966e36e28e - Doc<'doc>::as_str_slice::ha91bf39a19faeabdHVa
  10:     0x7f967421945f - loader::Context<'a>::extract_one::h945c702fbde346e3Eem
  11:     0x7f9674210acf - loader::Context<'a>::find_library_crate::h30971509c344ad3bD3l
  12:     0x7f96741f5f16 - loader::Context<'a>::load_library_crate::h0ade06e110892b81WSl
  13:     0x7f96741f4d99 - creader::CrateReader<'a>::resolve_crate::he1542772b02d0896E3j
  14:     0x7f96741f658d - creader::CrateReader<'a>::resolve_crate_deps::_$u7b$$u7b$closure$u7d$$u7d$::closure.38792
  15:     0x7f96741f633c - collections::hash::map::HashMap<K, V, S>.FromIterator<(K, V)>::from_iter::h12379182329167058746
  16:     0x7f96741f24dd - creader::CrateReader<'a>::register_crate::h62645edecf14372cTZj
  17:     0x7f96741f745c - creader::CrateReader<'a>::read_extension_crate::hb5e653870a478718Zak
  18:     0x7f96741f96b5 - creader::CrateReader<'a>::read_exported_macros::h2322639de24bfa4cUek
  19:     0x7f967421ed0d - macro_import::MacroLoader<'a>.Visitor<'v>::visit_item::hf3405d18ebfdd3eakYm
  20:     0x7f967421d88a - macro_import::read_macro_defs::h345dbb1da4180a9foXm
  21:     0x7f9676aced89 - driver::phase_2_configure_and_expand::h0bbd128ff132a80elBa
  22:     0x7f9676ab4b21 - driver::compile_input::h7ae6a86e23de0774Hca
  23:     0x7f9676aa5b47 - run_compiler::hb0408bcf47642fe6mPc
  24:     0x7f9676aa32c1 - sys_common::unwind::try::try_fn::h7614151098073783683
  25:     0x7f96765b9d1b - __rust_try
  26:     0x7f96765b21fd - sys_common::unwind::inner_try::hadd81c754a64f07ciYt
  27:     0x7f9676aa3b10 - boxed::F.FnBox<A>::call_box::h18261575856772421581
  28:     0x7f96765c3c59 - sys::thread::Thread::new::thread_start::h9bc812305b5e01feFPy
  29:     0x7f966f869181 - start_thread
  30:     0x7f967622a47c - __clone
  31:                0x0 - <unknown>

Could not compile `librdb`.

Caused by:
  Process didn't exit successfully: `rustc src/lib.rs --crate-name librdb --crate-type lib -g --cfg feature="default" --out-dir /mnt/data/src/rdb/target/debug --emit=dep-info,link -L dependency=/mnt/data/src/rdb/target/debug -L dependency=/mnt/data/src/rdb/target/debug/deps --extern libc=/mnt/data/src/rdb/target/debug/deps/liblibc-d2268fc21ed63f2c.rlib --extern log=/mnt/data/src/rdb/target/debug/deps/liblog-30a8a27ec161f1be.rlib --extern nix=/mnt/data/src/rdb/target/debug/deps/libnix-4281f0d4c5a4bab6.rlib --extern getopts=/mnt/data/src/rdb/target/debug/deps/libgetopts-852fe11dd444cf81.rlib -L native=/mnt/data/src/rdb/thirdparty/libdwarf/libdwarf -l static=dwarf -l elf -l z` (exit code: 101)

[azerupi]

I got the same error running cargo test (stable Rust 1.9) after running the tests with nightly using rustup run nightly cargo test.

It's probably unrelated but just before it panicked I set up the new error format with RUST_NEW_ERROR_FORMAT="true" in my .zshrc file. That's why I was building with nightly.

I have a file in tests/ looking like this

extern crate my_crate;

#[test]
...

And the panic did not occur when I commented out extern crate my_crate;. It also didn't occur when building normally with cargo build (on stable).

When I changed the code and it compiled with nightly I was able to compile with stable again.

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: run with `RUST_BACKTRACE=1` for a backtrace
thread 'rustc' panicked at 'called `Result::unwrap()` on an `Err` value: Utf8Error { valid_up_to: 0 }', ../src/libcore/result.rs:746
stack backtrace:
   1:     0x7fada89d8570 - std::sys::backtrace::tracing::imp::write::h4c73fcd3363076f5
   2:     0x7fada89e5c6b - std::panicking::default_hook::_$u7b$$u7b$closure$u7d$$u7d$::h0422dbb3077e6747
   3:     0x7fada89e580c - std::panicking::default_hook::haac48fa641db8fa2
   4:     0x7fada89aa79f - std::sys_common::unwind::begin_unwind_inner::h39d40f52add53ef7
   5:     0x7fada89ac888 - std::sys_common::unwind::begin_unwind_fmt::h64c0ff793199cc1b
   6:     0x7fada89d5d81 - rust_begin_unwind
   7:     0x7fada8a2f85f - core::panicking::panic_fmt::h73bf9d7e8e891a73
   8:     0x7fad9ff89a0b - core::result::unwrap_failed::h82c81d60621f70bd
   9:     0x7fad9ff8997e - rbml::Doc::as_str_slice::hd88d17b04c3f2cca
  10:     0x7fada67e0a62 - rustc_metadata::decoder::maybe_get_crate_hash::h1c0939ce4d9ba236
  11:     0x7fada681401b - rustc_metadata::loader::Context::extract_one::h56453781fb65bffa
  12:     0x7fada680aada - rustc_metadata::loader::Context::find_library_crate::h30ea71d32623d713
  13:     0x7fada67f1f96 - rustc_metadata::loader::Context::load_library_crate::h7787c1fa9559d604
  14:     0x7fada67f0e1f - rustc_metadata::creader::CrateReader::resolve_crate::h98decfaedbcfe12a
  15:     0x7fada67eab41 - _<creader..LocalCrateReader<'a, 'b> as rustc..hir..intravisit..Visitor<'hir>>::visit_item::h2f4b84ef1536be92
  16:     0x7fada67ff4be - rustc_metadata::creader::LocalCrateReader::read_crates::h7c2989bf6ef8974b
  17:     0x7fada8f21c86 - rustc_driver::driver::phase_3_run_analysis_passes::h83da042ec4b8ea10
  18:     0x7fada8ef6f9f - rustc_driver::driver::compile_input::h6491aaddd9e61258
  19:     0x7fada8edd4e4 - rustc_driver::run_compiler::h80b2ba5e4d787c5f
  20:     0x7fada8eda941 - std::sys_common::unwind::try::try_fn::h34e27823ddd1d5e9
  21:     0x7fada89d5d0b - __rust_try
  22:     0x7fada89d5c9d - std::sys_common::unwind::inner_try::h9eebd8dc83f388a6
  23:     0x7fada8edb18a - _<F as std..boxed..FnBox<A>>::call_box::h3d5d78986dfac5b2
  24:     0x7fada89e3e04 - std::sys::thread::Thread::new::thread_start::h471ad90789353b5b
  25:     0x7fada13ca473 - start_thread
  26:     0x7fada864269c - clone
  27:                0x0 - <unknown>

[alexcrichton]

cc @rust-lang/compiler

This seems to be getting lots of hits, is something that's fixed on nightly? Perhaps something that can be backported to beta?

[nikomatsakis]

@alexcrichton I'm not sure what's causing this -- you think it's a rustc bug?

[alexcrichton]

@nikomatsakis yes:

$ cargo new foo
$ cd foo
$ echo 'libc = "0.2"' >> Cargo.toml
$ rustup run nightly cargo build
...
$ rustup run stable cargo build
   Compiling libc v0.2.11
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
thread 'rustc' panicked at 'called `Result::unwrap()` on an `Err` value: Utf8Error { valid_up_to: 1 }', ../src/libcore/result.rs:746
note: Run with `RUST_BACKTRACE=1` for a backtrace.

error: Could not compile `libc`.

To learn more, run the command again with --verbose.

This may be fixed on both nightly and beta, as the only transition I can get to break is nightly to stable. I basically just want to confirm that we know what happened here and that it is indeed fixed and future-proofed.