error: internal compiler error: drop of untracked, uninitialized value

[sigmaSd]

Code

The panic happens here https://github.com/sigmaSd/konster/blob/ice/src/kmap.rs#L16

Meta

rustc --version --verbose:

rustc 1.57.0 (f1edd0429 2021-11-29)
binary: rustc
commit-hash: f1edd0429582dd29cccacaf50fd134b05593bd9c
commit-date: 2021-11-29
host: x86_64-unknown-linux-gnu
release: 1.57.0
LLVM version: 13.0.0

Error output

error: internal compiler error: compiler/rustc_mir_transform/src/elaborate_drops.rs:315:25: drop of untracked, uninitialized value bb8, place (((_1.0: kvec::KVec<(K, V), N>).0: [(K, V); N])[_22].1: V) (Parent(Some(mp32)))

Backtrace

error: internal compiler error: compiler/rustc_mir_transform/src/elaborate_drops.rs:315:25: drop of untracked, uninitialized value bb8, place (((_1.0: kvec::KVec<(K, V), N>).0: [(K, V); N])[_22].1: V) (Parent(Some(mp32)))
  --> src/kmap.rs:16:17
   |
16 |                 self.vec.buf[self.vec.cursor - 1].1 = value;
   |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

thread 'rustc' panicked at 'Box<dyn Any>', /rustc/f1edd0429582dd29cccacaf50fd134b05593bd9c/compiler/rustc_errors/src/lib.rs:1092:9
stack backtrace:
   0:     0x7f1b1f85da9c - std::backtrace_rs::backtrace::libunwind::trace::hf6a6dfd7da937cb0
                               at /rustc/f1edd0429582dd29cccacaf50fd134b05593bd9c/library/std/src/../../backtrace/src/backtrace/libunwind.rs:90:5
   1:     0x7f1b1f85da9c - std::backtrace_rs::backtrace::trace_unsynchronized::hc596a19e4891f7f3
                               at /rustc/f1edd0429582dd29cccacaf50fd134b05593bd9c/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
   2:     0x7f1b1f85da9c - std::sys_common::backtrace::_print_fmt::hb16700db31584325
                               at /rustc/f1edd0429582dd29cccacaf50fd134b05593bd9c/library/std/src/sys_common/backtrace.rs:67:5
   3:     0x7f1b1f85da9c - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::h231c4190cfa75162
                               at /rustc/f1edd0429582dd29cccacaf50fd134b05593bd9c/library/std/src/sys_common/backtrace.rs:46:22
   4:     0x7f1b1f8bafdc - core::fmt::write::h2a1462b5f8eea807
                               at /rustc/f1edd0429582dd29cccacaf50fd134b05593bd9c/library/core/src/fmt/mod.rs:1163:17
   5:     0x7f1b1f84dc05 - std::io::Write::write_fmt::h71ddfebc68685972
                               at /rustc/f1edd0429582dd29cccacaf50fd134b05593bd9c/library/std/src/io/mod.rs:1696:15
   6:     0x7f1b1f860f60 - std::sys_common::backtrace::_print::hcc197d4bebf2b369
                               at /rustc/f1edd0429582dd29cccacaf50fd134b05593bd9c/library/std/src/sys_common/backtrace.rs:49:5
   7:     0x7f1b1f860f60 - std::sys_common::backtrace::print::h335a66af06738c7c
                               at /rustc/f1edd0429582dd29cccacaf50fd134b05593bd9c/library/std/src/sys_common/backtrace.rs:36:9
   8:     0x7f1b1f860f60 - std::panicking::default_hook::{{closure}}::h6fac9ac9c8b79e52
                               at /rustc/f1edd0429582dd29cccacaf50fd134b05593bd9c/library/std/src/panicking.rs:210:50
   9:     0x7f1b1f860b15 - std::panicking::default_hook::h341c1030c6a1161b
                               at /rustc/f1edd0429582dd29cccacaf50fd134b05593bd9c/library/std/src/panicking.rs:227:9
  10:     0x7f1b2004d2b1 - rustc_driver::DEFAULT_HOOK::{{closure}}::{{closure}}::h932547f60770f26a
  11:     0x7f1b1f861779 - std::panicking::rust_panic_with_hook::h50680ff4b44510c6
                               at /rustc/f1edd0429582dd29cccacaf50fd134b05593bd9c/library/std/src/panicking.rs:628:17
  12:     0x7f1b202be00b - std::panicking::begin_panic::{{closure}}::h0125e1ff0bfe4e53
  13:     0x7f1b202bdfc6 - std::sys_common::backtrace::__rust_end_short_backtrace::hae1d67dea32e8035
  14:     0x7f1b2024ff0f - std::panicking::begin_panic::h521685e66fbb3433
  15:     0x7f1b202a740d - std::panic::panic_any::h9caaf7199e1644d6
  16:     0x7f1b202a33c5 - rustc_errors::HandlerInner::span_bug::hc9f0a930afc1d479
  17:     0x7f1b202a3640 - rustc_errors::Handler::span_bug::hc4af37c85eabc110
  18:     0x7f1b201f4bbd - rustc_middle::ty::context::tls::with_opt::h48190dd1f34ae5a2
  19:     0x7f1b201f6d80 - rustc_middle::util::bug::opt_span_bug_fmt::hcade798ef9e6d275
  20:     0x7f1b201f6d4c - rustc_middle::util::bug::span_bug_fmt::ha1d5b6fe1ca8882e
  21:     0x7f1b2133bf8f - <rustc_mir_transform::elaborate_drops::ElaborateDrops as rustc_middle::mir::MirPass>::run_pass::hb954d9506c1656cb
  22:     0x7f1b213632dc - rustc_mir_transform::run_passes::h0b0cae1798d554a0
  23:     0x7f1b21368e15 - rustc_mir_transform::run_post_borrowck_cleanup_passes::h34d80cbe976a7a80
  24:     0x7f1b213688f1 - rustc_mir_transform::mir_drops_elaborated_and_const_checked::he9672533e2b8a7b2
  25:     0x7f1b22295c9b - rustc_query_system::dep_graph::graph::DepGraph<K>::with_task::hceb6668af08c814b
  26:     0x7f1b2221a915 - rustc_data_structures::stack::ensure_sufficient_stack::h4ef639337d8f7956
  27:     0x7f1b217c44dc - rustc_query_system::query::plumbing::try_execute_query::hf3ffce6a38146ec3
  28:     0x7f1b21833d61 - <rustc_query_impl::Queries as rustc_middle::ty::query::QueryEngine>::mir_drops_elaborated_and_const_checked::ha3dc10083e60e48a
  29:     0x7f1b2126f630 - rustc_session::utils::<impl rustc_session::session::Session>::time::h8c394c39a2e108ce
  30:     0x7f1b21c57150 - rustc_interface::passes::analysis::h9fda1a8ae44d53e7
  31:     0x7f1b222713cf - rustc_query_system::dep_graph::graph::DepGraph<K>::with_task::h26e86d963a73dec8
  32:     0x7f1b22216609 - rustc_data_structures::stack::ensure_sufficient_stack::h135baf7277c4d193
  33:     0x7f1b2213aa7b - rustc_query_system::query::plumbing::try_execute_query::h0bf7639d3f58bfbd
  34:     0x7f1b22253232 - <rustc_query_impl::Queries as rustc_middle::ty::query::QueryEngine>::analysis::ha2144cf05b40d10d
  35:     0x7f1b21c4bca9 - rustc_interface::passes::QueryContext::enter::h0523b23606206a0b
  36:     0x7f1b21c32977 - rustc_interface::queries::<impl rustc_interface::interface::Compiler>::enter::hf84cd18c24bd5171
  37:     0x7f1b21c200ee - rustc_span::with_source_map::h6ab8a240e103b5b9
  38:     0x7f1b21c322ac - scoped_tls::ScopedKey<T>::set::hd1fbd64c6f645895
  39:     0x7f1b21c20ef5 - std::sys_common::backtrace::__rust_begin_short_backtrace::h0a1328c9fa7f7448
  40:     0x7f1b21c4c962 - core::ops::function::FnOnce::call_once{{vtable.shim}}::h4ea1ced06d6b3e97
  41:     0x7f1b1f86c933 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::h7bd677a5dc988be6
                               at /rustc/f1edd0429582dd29cccacaf50fd134b05593bd9c/library/alloc/src/boxed.rs:1691:9
  42:     0x7f1b1f86c933 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::h7b1c1ba11c4db785
                               at /rustc/f1edd0429582dd29cccacaf50fd134b05593bd9c/library/alloc/src/boxed.rs:1691:9
  43:     0x7f1b1f86c933 - std::sys::unix::thread::Thread::new::thread_start::h9c58c0d12d84e854
                               at /rustc/f1edd0429582dd29cccacaf50fd134b05593bd9c/library/std/src/sys/unix/thread.rs:106:17
  44:     0x7f1b1f766259 - start_thread
  45:     0x7f1b1f67b5e3 - __GI___clone
  46:                0x0 - <unknown>

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 1.57.0 (f1edd0429 2021-11-29) running on x86_64-unknown-linux-gnu

note: compiler flags: -C embed-bitcode=no -C debuginfo=2 -C linker=/usr/bin/clang -C incremental -C link-arg=-fuse-ld=/home/mrcool/dev/bin/mold --crate-type lib

note: some of the compiler flags provided by cargo are hidden

query stack during panic:
#0 [mir_drops_elaborated_and_const_checked] elaborating drops for `kmap::<impl at src/kmap.rs:9:1: 24:2>::insert`
#1 [analysis] running analysis passes on this crate
end of query stack

[5225225]

I can't seem to reproduce this locally, does it go away if you update your compiler?

[sigmaSd]

Current compiler is: rustc 1.57.0 (f1edd04 2021-11-29)

And the same happens when I use beta and nightly:

beta: cargo 1.56.0-beta (18751dd3f 2021-09-01)
nightly: cargo 1.57.0-nightly (9a28ac83c 2021-09-18)

I remembered I was using mold linker (https://github.com/rui314/mold) but I switched to the default linker and the same happens, other then that my setup is normal

[sigmaSd]

Actually I can confirm its reproducible, I just tried it with https://gitpod.io/ and the same thing happens

maybe you didn't checkout the ice branch?

[5225225]

Ahhh, oops. Didn't notice it was on a different branch. Sorry, my bad! Yes, I can reproduce it fine locally.

[ecstatic-morse]

MCVE:

struct S<T>([T; 1]);

impl<K, V> S<(K, V)> {
    pub const fn foo(mut self, value: V) -> Self {
        let _arr = self.0;
        self.0[0].1 = value; //~ move
        self
    }
}

fn main() {}

This code has move errors and fails const-checking, just like the original example. The ICE occurs after errors are emitted. @sigmaSd did you truncate the logs in your original post?

One option is to change the following statement to delay_span_bug:

rust/compiler/rustc_mir_transform/src/elaborate_drops.rs

Lines 319 to 325 in 753e569

	span_bug!(
	terminator.source_info.span,
	"drop of untracked, uninitialized value {:?}, place {:?} ({:?})",
	bb,
	place,
	path
	);

It's a weird that the ICE only occurs only in a const-context though, perhaps there's a better way to fix this?

For the non-const version, we abort before we ever get to drop elaboration due to the errors, though I'm not sure why.

[tmiasko]

For the non-const version, we abort before we ever get to drop elaboration due to the errors, though I'm not sure why.

For const items mir_drops_elaborated_and_const_checked is queried earlier, without an intermediate exit point:

rust/compiler/rustc_interface/src/passes.rs

Lines 950 to 977 in 753e569

	sess.time("MIR_borrow_checking", || {
	tcx.hir().par_body_owners(|def_id| tcx.ensure().mir_borrowck(def_id));
	});
	sess.time("MIR_effect_checking", || {
	for def_id in tcx.hir().body_owners() {
	tcx.ensure().thir_check_unsafety(def_id);
	if !tcx.sess.opts.debugging_opts.thir_unsafeck {
	rustc_mir_transform::check_unsafety::check_unsafety(tcx, def_id);
	}
	if tcx.hir().body_const_context(def_id).is_some() {
	tcx.ensure()
	.mir_drops_elaborated_and_const_checked(ty::WithOptConstParam::unknown(def_id));
	}
	}
	});
	sess.time("layout_testing", || layout_test::test_layout(tcx));
	// Avoid overwhelming user with errors if borrow checking failed.
	// I'm not sure how helpful this is, to be honest, but it avoids a
	// lot of annoying errors in the ui tests (basically,
	// lint warnings and so on -- kindck used to do this abort, but
	// kindck is gone now). -nmatsakis
	if sess.has_errors() {
	return Err(ErrorReported);
	}

[sigmaSd]

@ecstatic-morse yes the error log is truncated, I have a move error error[E0382]: assign to part of moved value: self.vec.buf