Spurious access violation (exit code: 3221225477) when compiling libsyntax with MSVC

[kennytm]

Symptom: On MSVC builders (Windows), when compiling libsyntax in either stage0 or stage1, the compiler rustc will crash with exit code 3221225477 (= 0xc0000005 = access violation).

We suspect this is related to #50329 (merged at 2018-05-02T10:13:06Z).

Sample crash log

error: Could not compile `syntax`.
Caused by:
  process didn't exit successfully: `C:\projects\rust\build\bootstrap/debug/rustc --crate-name syntax libsyntax\lib.rs --color always --error-format json --crate-type dylib --emit=dep-info,link -C prefer-dynamic -C opt-level=3 -C metadata=7ac7668085f2897f -C extra-filename=-7ac7668085f2897f --out-dir C:\projects\rust\build\i686-pc-windows-msvc\stage0-rustc\i686-pc-windows-msvc\release\deps --target i686-pc-windows-msvc -L dependency=C:\projects\rust\build\i686-pc-windows-msvc\stage0-rustc\i686-pc-windows-msvc\release\deps -L dependency=C:\projects\rust\build\i686-pc-windows-msvc\stage0-rustc\release\deps --extern bitflags=C:\projects\rust\build\i686-pc-windows-msvc\stage0-rustc\i686-pc-windows-msvc\release\deps\libbitflags-9ba1f7028730cd0a.rlib --extern log=C:\projects\rust\build\i686-pc-windows-msvc\stage0-rustc\i686-pc-windows-msvc\release\deps\liblog-001e68131969f2ec.rlib --extern rustc_errors=C:\projects\rust\build\i686-pc-windows-msvc\stage0-rustc\i686-pc-windows-msvc\release\deps\rustc_errors-ffee8b3fc130b2b1.dll --extern syntax_pos=C:\projects\rust\build\i686-pc-windows-msvc\stage0-rustc\i686-pc-windows-msvc\release\deps\syntax_pos-1048adc53f632b89.dll --extern rustc_data_structures=C:\projects\rust\build\i686-pc-windows-msvc\stage0-rustc\i686-pc-windows-msvc\release\deps\rustc_data_structures-3a7257003acd8e8b.dll --extern scoped_tls=C:\projects\rust\build\i686-pc-windows-msvc\stage0-rustc\i686-pc-windows-msvc\release\deps\libscoped_tls-49f5fac2ae1c97d0.rlib --extern serialize=C:\projects\rust\build\i686-pc-windows-msvc\stage0-rustc\i686-pc-windows-msvc\release\deps\serialize-f37b7ca68fe29329.dll --extern serialize=C:\projects\rust\build\i686-pc-windows-msvc\stage0-rustc\i686-pc-windows-msvc\release\deps\libserialize-f37b7ca68fe29329.rlib --extern rustc_target=C:\projects\rust\build\i686-pc-windows-msvc\stage0-rustc\i686-pc-windows-msvc\release\deps\rustc_target-63878e92b639df83.dll` (exit code: 3221225477)
command did not execute successfully: "C:\\projects\\rust\\build\\i686-pc-windows-msvc\\stage0/bin\\cargo.exe" "build" "--target" "i686-pc-windows-msvc" "-j" "4" "--release" "--locked" "--color" "always" "--features" "" "--manifest-path" "C:\\projects\\rust\\src/rustc/Cargo.toml" "--message-format" "json"
expected success, got: exit code: 101
thread 'main' panicked at 'cargo must succeed', bootstrap\compile.rs:1091:9
note: Run with `RUST_BACKTRACE=1` for a backtrace.

First seen on the following PRs:

• Update rls with compiling clippy #50503 (comment) (2018-05-07T21:14:30Z)
• added missing implementation hint #50161 (comment) (2018-05-10T07:52:11Z)

cc #33434 (parent issue)

[ishitatsuyuki]

cc @Zoxc Can you try to reproduce?

[Zoxc]

I haven't seen this locally. Does it happen often?

[kennytm]

As shown in the post, twice in the last 8 days so far. There are 3 other segfaults on Windows which might also be attributed here (#50000 (comment), #50418 (comment), #50466 (comment)).

[ishitatsuyuki]

Have this occurred this week?