ICE building panic_unwind (stage 1) in debug mode with incremental compilation

[abonander]

• fresh clone of master
• using local Rust and Cargo latest nightly (also occurs in beta-1.25.0),
• MSVC x64 with Visual Studio 2017

In config.toml:

• set build.cargo and build.rustc to Rustup's proxies
• set rust.debug = true (happens only in debug mode)
• set codegen-units = 0 (specific value doesn't appear to affect the issue)
• run x.py build

It gets to this point and ICEs:

Building stage1 std artifacts (x86_64-pc-windows-msvc -> x86_64-pc-windows-msvc)
   Compiling core v0.0.0 (file:///C:/Users/cyber/Rust/rust/src/libcore)
   Compiling cc v1.0.6
   Compiling unwind v0.0.0 (file:///C:/Users/cyber/Rust/rust/src/libunwind)
   Compiling cfg-if v0.1.2
   Compiling filetime v0.1.15
   Compiling build_helper v0.1.0 (file:///C:/Users/cyber/Rust/rust/src/build_helper)
   Compiling compiler_builtins v0.0.0 (file:///C:/Users/cyber/Rust/rust/src/rustc/compiler_builtins_shim)
   Compiling alloc_jemalloc v0.0.0 (file:///C:/Users/cyber/Rust/rust/src/liballoc_jemalloc)
   Compiling std v0.0.0 (file:///C:/Users/cyber/Rust/rust/src/libstd)
   Compiling std_unicode v0.0.0 (file:///C:/Users/cyber/Rust/rust/src/libstd_unicode)
   Compiling libc v0.0.0 (file:///C:/Users/cyber/Rust/rust/src/rustc/libc_shim)
   Compiling panic_abort v0.0.0 (file:///C:/Users/cyber/Rust/rust/src/libpanic_abort)
   Compiling alloc v0.0.0 (file:///C:/Users/cyber/Rust/rust/src/liballoc)
   Compiling panic_unwind v0.0.0 (file:///C:/Users/cyber/Rust/rust/src/libpanic_unwind)
   Compiling alloc_system v0.0.0 (file:///C:/Users/cyber/Rust/rust/src/liballoc_system)
�[0m�[38;5;9m�[1merror: internal compiler error�[0m�[0m�[38;5;15m�[1m: librustc\ty\maps\on_disk_cache.rs:830: alloc id without corresponding allocation: 39�[0m

thread 'rustc' panicked at 'Box<Any>', librustc_errors\lib.rs:543:9
note: Run with `RUST_BACKTRACE=1` for a backtrace.

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-dev running on x86_64-pc-windows-msvc

note: compiler flags: -Z force-unstable-if-unmarked -C debug-assertions=off -C overflow-checks=on -C incremental -C prefer-dynamic -C debug-assertions=y -C codegen-units=8 -C target-feature=+crt-static --crate-type lib

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

error: Could not compile `panic_unwind`.

Caused by:
  process didn't exit successfully: `C:\Users\cyber\Rust\rust\build\bootstrap/debug/rustc --crate-name panic_unwind libpanic_unwind\lib.rs --error-format json --crate-type lib --emit=dep-info,link -C debug-assertions=off -C overflow-checks=on -C metadata=730d0c4f6ad8f657 -C extra-filename=-730d0c4f6ad8f657 --out-dir C:\Users\cyber\Rust\rust\build\x86_64-pc-windows-msvc\stage1-std\x86_64-pc-windows-msvc\debug\deps --target x86_64-pc-windows-msvc -C incremental=C:\Users\cyber\Rust\rust\build\x86_64-pc-windows-msvc\stage1-std\x86_64-pc-windows-msvc\debug\incremental -L dependency=C:\Users\cyber\Rust\rust\build\x86_64-pc-windows-msvc\stage1-std\x86_64-pc-windows-msvc\debug\deps -L dependency=C:\Users\cyber\Rust\rust\build\x86_64-pc-windows-msvc\stage1-std\debug\deps --extern alloc=C:\Users\cyber\Rust\rust\build\x86_64-pc-windows-msvc\stage1-std\x86_64-pc-windows-msvc\debug\deps\liballoc-0ac88ae22893c7ce.rlib --extern unwind=C:\Users\cyber\Rust\rust\build\x86_64-pc-windows-msvc\stage1-std\x86_64-pc-windows-msvc\debug\deps\libunwind-75ec301683f1f6ba.rlib --extern core=C:\Users\cyber\Rust\rust\build\x86_64-pc-windows-msvc\stage1-std\x86_64-pc-windows-msvc\debug\deps\libcore-814295c4539117a2.rlib --extern libc=C:\Users\cyber\Rust\rust\build\x86_64-pc-windows-msvc\stage1-std\x86_64-pc-windows-msvc\debug\deps\liblibc-766a10703183d997.rlib` (exit code: 101)
warning: build failed, waiting for other jobs to finish...

I grepped the error message (alloc id without corresponding allocation) and it points to this line which appears to be associated with incremental compilation, which makes sense because this only triggers when building in debug mode and setting CARGO_INCREMENTAL=false avoids the ICE.

cc @alexcrichton rust-lang/cargo#4817

[oli-obk]

There's a very high chance that this is fixed by #49079

[abonander]

I'll try to build the latest master and see what happens.

[abonander]

@oli-obk Nope, just changed the file the error is emitted from. 😕

Building stage1 std artifacts (x86_64-pc-windows-msvc -> x86_64-pc-windows-msvc)
   Compiling cc v1.0.6
   Compiling core v0.0.0 (file:///C:/Users/cyber/Rust/rust/src/libcore)
   Compiling cfg-if v0.1.2
   Compiling unwind v0.0.0 (file:///C:/Users/cyber/Rust/rust/src/libunwind)
   Compiling filetime v0.1.15
   Compiling build_helper v0.1.0 (file:///C:/Users/cyber/Rust/rust/src/build_helper)
   Compiling compiler_builtins v0.0.0 (file:///C:/Users/cyber/Rust/rust/src/rustc/compiler_builtins_shim)
   Compiling std v0.0.0 (file:///C:/Users/cyber/Rust/rust/src/libstd)
   Compiling alloc_jemalloc v0.0.0 (file:///C:/Users/cyber/Rust/rust/src/liballoc_jemalloc)
   Compiling libc v0.0.0 (file:///C:/Users/cyber/Rust/rust/src/rustc/libc_shim)
   Compiling std_unicode v0.0.0 (file:///C:/Users/cyber/Rust/rust/src/libstd_unicode)
   Compiling panic_abort v0.0.0 (file:///C:/Users/cyber/Rust/rust/src/libpanic_abort)
   Compiling alloc v0.0.0 (file:///C:/Users/cyber/Rust/rust/src/liballoc)
   Compiling panic_unwind v0.0.0 (file:///C:/Users/cyber/Rust/rust/src/libpanic_unwind)
   Compiling alloc_system v0.0.0 (file:///C:/Users/cyber/Rust/rust/src/liballoc_system)
�[0m�[38;5;9m�[1merror: internal compiler error�[0m�[0m�[38;5;15m�[1m: librustc\mir\interpret\mod.rs:184: alloc id without corresponding allocation: 39�[0m

thread 'rustc' panicked at 'Box<Any>', librustc_errors\lib.rs:543:9
note: Run with `RUST_BACKTRACE=1` for a backtrace.

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-dev running on x86_64-pc-windows-msvc

note: compiler flags: -Z force-unstable-if-unmarked -C debug-assertions=off -C overflow-checks=on -C incremental -C prefer-dynamic -C debug-assertions=y -C codegen-units=8 -C target-feature=+crt-static --crate-type lib

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

error: Could not compile `panic_unwind`.

Caused by:
  process didn't exit successfully: `C:\Users\cyber\Rust\rust\build\bootstrap/debug/rustc --crate-name panic_unwind libpanic_unwind\lib.rs --error-format json --crate-type lib --emit=dep-info,link -C debug-assertions=off -C overflow-checks=on -C metadata=730d0c4f6ad8f657 -C extra-filename=-730d0c4f6ad8f657 --out-dir C:\Users\cyber\Rust\rust\build\x86_64-pc-windows-msvc\stage1-std\x86_64-pc-windows-msvc\debug\deps --target x86_64-pc-windows-msvc -C incremental=C:\Users\cyber\Rust\rust\build\x86_64-pc-windows-msvc\stage1-std\x86_64-pc-windows-msvc\debug\incremental -L dependency=C:\Users\cyber\Rust\rust\build\x86_64-pc-windows-msvc\stage1-std\x86_64-pc-windows-msvc\debug\deps -L dependency=C:\Users\cyber\Rust\rust\build\x86_64-pc-windows-msvc\stage1-std\debug\deps --extern core=C:\Users\cyber\Rust\rust\build\x86_64-pc-windows-msvc\stage1-std\x86_64-pc-windows-msvc\debug\deps\libcore-814295c4539117a2.rlib --extern alloc=C:\Users\cyber\Rust\rust\build\x86_64-pc-windows-msvc\stage1-std\x86_64-pc-windows-msvc\debug\deps\liballoc-0ac88ae22893c7ce.rlib --extern libc=C:\Users\cyber\Rust\rust\build\x86_64-pc-windows-msvc\stage1-std\x86_64-pc-windows-msvc\debug\deps\liblibc-766a10703183d997.rlib --extern unwind=C:\Users\cyber\Rust\rust\build\x86_64-pc-windows-msvc\stage1-std\x86_64-pc-windows-msvc\debug\deps\libunwind-75ec301683f1f6ba.rlib` (exit code: 101)
warning: build failed, waiting for other jobs to finish...
error: build failed
thread 'main' panicked at 'command did not execute successfully: "C:/Users/cyber/.cargo/bin/cargo.exe" "build" "--target" "x86_64-pc-windows-msvc" "-j" "8" "--features" "panic-unwind debug-jemalloc backtrace" "--manifest-path" "C:\\Users\\cyber\\Rust\\rust\\src/libstd/Cargo.toml" "--message-format" "json"
expected success, got: exit code: 101', bootstrap\compile.rs:1096:9
note: Run with `RUST_BACKTRACE=1` for a backtrace.
failed to run: C:\Users\cyber\Rust\rust\build\bootstrap\debug\bootstrap build
Build completed unsuccessfully in 0:25:34

I have the backtrace here if you like but it's more than 100 frames deep so I don't know how much context you need.

[oli-obk]

Thanks. I'll have a look. No need for a backtrace

[oli-obk]

Repro:

extern "C" {
    pub static __ImageBase: u8;
}

pub static FOO: &'static u8 = unsafe { &__ImageBase };

The problem is that extern statics don't have allocations (because it makes no sense for them to have usable memory during const evaluation).

This is easy to fix :)