crash while compiling pango 0.1.3

[matthiaskrgr]

I was trying to build https://github.com/bvinc/gxi which pulls in pango 0.1.3 as dependency https://github.com/gtk-rs/pango .
While building pango, rustc segfaults

cd /tmp/
cargo new pango_crash --bin
cd pango_crash
echo "pango = \"0.1.3\"" >> Cargo.toml
RUST_BACKTRACE=1 cargo build --verbose

   Compiling pango v0.1.3
     Running `rustc --crate-name pango /home/matthias/.cargo/registry/src/github.com-1ecc6299db9ec823/pango-0.1.3/src/lib.rs --crate-type lib --emit=dep-info,link -C debuginfo=2 -C metadata=79ef8578d5682787 -C extra-filename=-79ef8578d5682787 --out-dir /tmp/pango_crash/target/debug/deps -L dependency=/tmp/pango_crash/target/debug/deps --extern libc=/tmp/pango_crash/target/debug/deps/liblibc-a4fb9588d5f009f2.rlib --extern glib=/tmp/pango_crash/target/debug/deps/libglib-b20a4586cffe6411.rlib --extern pango_sys=/tmp/pango_crash/target/debug/deps/libpango_sys-954f223c59579c4f.rlib --extern bitflags=/tmp/pango_crash/target/debug/deps/libbitflags-ace94e42abe55a1c.rlib --cap-lints allow -L native=/usr/lib -L native=/usr/lib -L native=/usr/lib`
thread 'rustc' panicked at 'called `Option::unwrap()` on a `None` value', libcore/option.rs:335:21
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 libstd/sys/unix/backtrace/tracing/gcc_s.rs:49
   1: std::sys_common::backtrace::print
             at libstd/sys_common/backtrace.rs:71
             at libstd/sys_common/backtrace.rs:59
   2: std::panicking::default_hook::{{closure}}
             at libstd/panicking.rs:207
   3: std::panicking::default_hook
             at libstd/panicking.rs:223
   4: core::ops::function::Fn::call
   5: std::panicking::rust_panic_with_hook
             at libstd/panicking.rs:403
   6: std::panicking::begin_panic_fmt
             at libstd/panicking.rs:349
   7: rust_begin_unwind
             at libstd/panicking.rs:325
   8: core::panicking::panic_fmt
             at libcore/panicking.rs:72
   9: core::panicking::panic
             at libcore/panicking.rs:51
  10: rustc_mir::hair::pattern::PatternContext::const_to_pat
  11: rustc_mir::hair::pattern::PatternContext::lower_path
  12: rustc_mir::hair::pattern::PatternContext::lower_pattern
  13: core::ops::function::impls::<impl core::ops::function::FnOnce<A> for &'a mut F>::call_once
  14: <alloc::vec::Vec<T> as alloc::vec::SpecExtend<T, I>>::from_iter
  15: <alloc::vec::Vec<T> as alloc::vec::SpecExtend<T, I>>::from_iter
  16: <rustc_mir::hair::pattern::check_match::MatchVisitor<'a, 'tcx> as rustc::hir::intravisit::Visitor<'tcx>>::visit_expr
  17: <rustc_mir::hair::pattern::check_match::MatchVisitor<'a, 'tcx> as rustc::hir::intravisit::Visitor<'tcx>>::visit_expr
  18: rustc::session::Session::track_errors
  19: rustc_mir::hair::pattern::check_match::check_match
  20: rustc::dep_graph::graph::DepGraph::with_task_impl
  21: rustc_errors::Handler::track_diagnostics
  22: rustc::ty::maps::plumbing::<impl rustc::ty::context::TyCtxt<'a, 'gcx, 'tcx>>::cycle_check
  23: rustc::ty::maps::<impl rustc::ty::maps::queries::check_match<'tcx>>::force
  24: rustc::ty::maps::<impl rustc::ty::maps::queries::check_match<'tcx>>::try_get
  25: rustc::ty::maps::TyCtxtAt::check_match
  26: rustc::ty::maps::<impl rustc::ty::context::TyCtxt<'a, 'tcx, 'lcx>>::check_match
  27: rustc::hir::intravisit::Visitor::visit_nested_body
  28: rustc::hir::Crate::visit_all_item_likes
  29: rustc_mir::hair::pattern::check_match::check_crate
  30: <std::thread::local::LocalKey<T>>::with
  31: <std::thread::local::LocalKey<T>>::with
  32: rustc::ty::context::TyCtxt::create_and_enter
  33: rustc_driver::driver::compile_input
  34: rustc_driver::run_compiler_impl
  35: syntax::with_globals
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 1.26.0-nightly (5508b2714 2018-03-18) running on x86_64-unknown-linux-gnu
note: compiler flags: -C debuginfo=2 --crate-type lib
note: some of the compiler flags provided by cargo are hidden
error: Could not compile `pango`.
Caused by:
  process didn't exit successfully: `rustc --crate-name pango /home/matthias/.cargo/registry/src/github.com-1ecc6299db9ec823/pango-0.1.3/src/lib.rs --crate-type lib --emit=dep-info,link -C debuginfo=2 -C metadata=79ef8578d5682787 -C extra-filename=-79ef8578d5682787 --out-dir /tmp/pango_crash/target/debug/deps -L dependency=/tmp/pango_crash/target/debug/deps --extern libc=/tmp/pango_crash/target/debug/deps/liblibc-a4fb9588d5f009f2.rlib --extern glib=/tmp/pango_crash/target/debug/deps/libglib-b20a4586cffe6411.rlib --extern pango_sys=/tmp/pango_crash/target/debug/deps/libpango_sys-954f223c59579c4f.rlib --extern bitflags=/tmp/pango_crash/target/debug/deps/libbitflags-ace94e42abe55a1c.rlib --cap-lints allow -L native=/usr/lib -L native=/usr/lib -L native=/usr/lib` (exit code: 101)

meta:

rustc 1.26.0-nightly (5508b2714 2018-03-18)
binary: rustc
commit-hash: 5508b27145cfb82896ae838e6aca0cd48750796f
commit-date: 2018-03-18
host: x86_64-unknown-linux-gnu
release: 1.26.0-nightly
LLVM version: 6.0

[oli-obk]

Crash happens in https://github.com/rust-lang/rust/blob/9b15ddb/src/librustc_mir/hair/pattern/mod.rs#L857-L860

So apparently const eval produces a discriminant that doesn't match any variant's discriminant.

more concretely, it happens during a match on https://github.com/gtk-rs/sys/blob/af83826e0a31f68bcddee17d3791fb01453dc632/pango-sys/src/lib.rs#L222 which is the only discriminant with -1 as its value.

[matthiaskrgr]

@oli-obk weird, I am still getting the panic with todays nightly rustc 1.26.0-nightly (c08480fce 2018-03-23) :(

[oli-obk]

Same backtrace? We do have a regression test for this exact issue

[matthiaskrgr]

Yeah, backtrace is identical except for the rustc version string in the ICE notes. :/