Many attempted to read undefined bytes errors with miri

[bjorn3]

error: attempted to read undefined bytes

ERROR 2018-05-26T14:44:50Z: rustc_mir::interpret::eval_context: 

An error occurred in miri:
backtrace frames: 27
0: backtrace::backtrace::trace::h85503c2e4e338460
	at <unknown_file>
1: backtrace::capture::Backtrace::new_unresolved::h51246d60a53a8bdc
	at <unknown_file>
2: _$LT$rustc..mir..interpret..error..EvalError$LT$$u27$tcx$GT$$u20$as$u20$core..convert..From$LT$rustc..mir..interpret..error..EvalErrorKind$LT$$u27$tcx$C$$u20$u64$GT$$GT$$GT$::from::h4d30d3209764fd49
	at <unknown_file>
3: rustc::mir::interpret::value::Scalar::to_bits::h85909ebea5cc3804
	at <unknown_file>
4: rustc_mir::interpret::terminator::_$LT$impl$u20$rustc_mir..interpret..eval_context..EvalContext$LT$$u27$a$C$$u20$$u27$mir$C$$u20$$u27$tcx$C$$u20$M$GT$$GT$::eval_terminator::h69abb3bb79aab288
	at /Users/travis/build/rust-lang/rust/src/librustc_mir/interpret/terminator/mod.rs:47
5: rustc_mir::interpret::step::_$LT$impl$u20$rustc_mir..interpret..eval_context..EvalContext$LT$$u27$a$C$$u20$$u27$mir$C$$u20$$u27$tcx$C$$u20$M$GT$$GT$::terminator::hdd1ce4d831f07250
	at /Users/travis/build/rust-lang/rust/src/librustc_mir/interpret/step.rs:109
6: rustc_mir::interpret::step::_$LT$impl$u20$rustc_mir..interpret..eval_context..EvalContext$LT$$u27$a$C$$u20$$u27$mir$C$$u20$$u27$tcx$C$$u20$M$GT$$GT$::step::h7b4b7c429541cd9b
	at /Users/travis/build/rust-lang/rust/src/librustc_mir/interpret/step.rs:43
7: miri::eval_main::run_main::h9c72be881571a562
	at src/lib.rs:232
8: miri::eval_main::h9d8ab3b0d25eb037
	at src/lib.rs:245
9: miri::after_analysis::h1dc1a8379cb87900
	at src/bin/miri.rs:147
10: _$LT$miri..MiriCompilerCalls$u20$as$u20$rustc_driver..CompilerCalls$LT$$u27$a$GT$$GT$::build_controller::_$u7b$$u7b$closure$u7d$$u7d$::hbed7da9498dc169f
	at src/bin/miri.rs:88
11: rustc::ty::context::tls::with_context::h434a73bf87917666
	at <unknown_file>
12: rustc_driver::driver::compile_input::_$u7b$$u7b$closure$u7d$$u7d$::h54692425a596d732
	at <unknown_file>
13: rustc::ty::context::tls::enter_context::hdfa81ea4757b9ad4
	at <unknown_file>
14: _$LT$std..thread..local..LocalKey$LT$T$GT$$GT$::with::hfbf5029193cab3f2
	at <unknown_file>
15: rustc::ty::context::TyCtxt::create_and_enter::hfc13991376fb466d
	at <unknown_file>
16: rustc_driver::driver::compile_input::he7ba295ba0b6472f
	at <unknown_file>
17: rustc_driver::run_compiler_with_pool::h39dace11c41da12a
	at <unknown_file>
18: syntax::with_globals::h39d73970aba4a7ab
	at <unknown_file>
19: rustc_driver::run_compiler::hf76541365053c7e0
	at <unknown_file>
20: miri::main::hd88a1c4b352e05a3
	at src/bin/miri.rs:237
21: std::rt::lang_start::_$u7b$$u7b$closure$u7d$$u7d$::hf5b1442a7c729874
	at /Users/travis/build/rust-lang/rust/src/libstd/rt.rs:74
22: std::panicking::try::do_call::hfd75cf9e05cc5943 (.llvm.9696875478146817961)
	at <unknown_file>
23: __rust_maybe_catch_panic
	at <unknown_file>
24: std::rt::lang_start_internal::h36f7afe722d0078f
	at <unknown_file>
25: std::rt::lang_start::he4af6349eec3f416
	at /Users/travis/build/rust-lang/rust/src/libstd/rt.rs:74
26: main
	at <unknown_file>

error[E0080]: constant evaluation error
   --> /Users/bjorn/.rustup/toolchains/nightly-x86_64-apple-darwin/lib/rustlib/src/rust/src/libcore/result.rs:747:13
    |
747 |             Ok(t) => t,
    |             ^^^^^ attempted to read undefined bytes
    |
note: inside call to `<std::result::Result<T, E>><(), std::collections::CollectionAllocErr>::unwrap_or_else::<[closure@DefId(4/1:226 ~ alloc[e00a]::raw_vec[0]::{{impl}}[0]::allocate_in[0]::{{closure}}[1])]>`
   --> /Users/bjorn/.rustup/toolchains/nightly-x86_64-apple-darwin/lib/rustlib/src/rust/src/liballoc/raw_vec.rs:92:13
    |
92  |             alloc_guard(alloc_size).unwrap_or_else(|_| capacity_overflow());
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
note: inside call to `<alloc::raw_vec::RawVec<T, A>><(), std::heap::Global>::allocate_in`
   --> /Users/bjorn/.rustup/toolchains/nightly-x86_64-apple-darwin/lib/rustlib/src/rust/src/liballoc/raw_vec.rs:146:9
    |
146 |         RawVec::allocate_in(cap, false, Global)
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
note: inside call to `<alloc::raw_vec::RawVec<T>><()>::with_capacity`
   --> /Users/bjorn/.rustup/toolchains/nightly-x86_64-apple-darwin/lib/rustlib/src/rust/src/liballoc/vec.rs:362:18
    |
362 |             buf: RawVec::with_capacity(capacity),
    |                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
note: inside call to `<std::vec::Vec<T>><()>::with_capacity`
   --> /Users/bjorn/.rustup/toolchains/nightly-x86_64-apple-darwin/lib/rustlib/src/rust/src/liballoc/binary_heap.rs:342:28
    |
342 |         BinaryHeap { data: Vec::with_capacity(capacity) }
    |                            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
note: inside call to `<std::collections::BinaryHeap<T>><()>::with_capacity`
   --> tests/run-pass/zero-sized-binary-heap-push.rs:18:26
    |
18  |         let mut tester = BinaryHeap::with_capacity(len);
    |                          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

[bjorn3]

cc @oli-obk

[bjorn3]

Error is at

rust/src/librustc_mir/interpret/terminator/mod.rs

Lines 44 to 47 in 990d8aa

	let mut target_block = targets[targets.len() - 1];
	for (index, &const_int) in values.iter().enumerate() {
	if discr_prim.to_bits(self.layout_of(discr_val.ty).unwrap().size)? == const_int {

[bjorn3]

According to priroda discr_prim has 8 bits of defined bytes. And it has the type isize, which has 64 bits.

[bjorn3]

#50967 (review)