Option::unwrap() on a None value

[rnarubin]

I ran into a panic when building a crate with rustc's self-profiling:

thread 'rustc' panicked at 'called `Option::unwrap()` on a `None` value', /cargo/registry/src/github.com-1ecc6299db9ec823/measureme-9.1.0/src/stringtable.rs:105:62
stack backtrace:
   0: rust_begin_unwind
             at /rustc/8f349be27815d43d462a32faeb270a22a68486b6/library/std/src/panicking.rs:493:5
   1: core::panicking::panic_fmt
             at /rustc/8f349be27815d43d462a32faeb270a22a68486b6/library/core/src/panicking.rs:92:14
   2: core::panicking::panic
             at /rustc/8f349be27815d43d462a32faeb270a22a68486b6/library/core/src/panicking.rs:50:5
   3: measureme::stringtable::StringTableBuilder::alloc
   4: measureme::event_id::EventIdBuilder::from_label_and_arg
   5: rustc_data_structures::profiling::SelfProfilerRef::with_profiler
   6: rustc_query_impl::profiling_support::alloc_self_profile_query_strings
   7: rustc_interface::passes::QueryContext::enter
   8: rustc_interface::queries::<impl rustc_interface::interface::Compiler>::enter
   9: rustc_span::with_source_map
  10: rustc_interface::interface::create_compiler_and_run
  11: rustc_span::with_session_globals
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

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/issues/new?labels=C-bug%2C+I-ICE%2C+T-compiler&template=ice.md

note: rustc 1.52.0-nightly (8f349be27 2021-03-08) running on x86_64-unknown-linux-gnu

note: compiler flags: -Z self-profile -Z self-profile-events=default,args -C embed-bitcode=no -C debuginfo=2 -C incremental --crate-type bin

This doesn't appear related to #149 as the unwrap happens in totally different code

[bjorn3]

Which crate did you compile? Based on the error location it seems like there was an overflow in calculating a StringId, which could be caused by too many strings in the profile I guess.

[rnarubin]

It's a private crate so unfortunately I can't share it directly. I'm trying to narrow down a minimal reproduction now.

For what it's worth, there's definitely something anomalous in my code (or rustc's handling of it), because rustc is taking 14+ minutes to build it, while just a few changes ago it was about 40 seconds. That's why i was trying to profile in the first place! I'll try to narrow down a cause

[rylev]

@rnarubin I'm going to close this for now. Can you reopen if you found a reproducible case?