wasm32-wasip1 Exit Code Reproducer

FIXED This has been fixed in 130554 and is scheduled to be included in the Rust 1.83 release (it is currently available in the Rust 1.83-nightly build).

This repository contains tests and code to reproduce an issue with WASM/WASI (preview 1) artifacts producing unexpected exit code values when using the Rust Standary Library's std::process::ExitCode vs std::process::exit.

There are two simple examples, exit-with-process, which uses std::process::exit, and exit-with-exit-code, which uses std::process::ExitCode. Each example may be executed on its own, compiled for the host platform.

When compiled as a standard binary on the host system, the exit codes are returned as expected. When compiled with wasm32-wasip1, the use of ExitCode results in the exit code of 1, regardless of the value provided to ExitCode::from.

Note that the tool chain may be passed as an additional parameter to the just commands listed below.

Building

Build the two applications using either

$ just build-all-binary

or directly with

$ cargo rustc \
    --manifest-path $BIN_NAME/Cargo.toml \
    --release \
    -- \
    -C panic=abort \
    -C opt-level=z \
    -C codegen-units=1

where $BIN_NAME is one of [exit-with-process, exit-with-exit-code].

These rustc configuration options match what is being used when compiling the code to wasm32-wasi.

exit-with-process

This example produces the exit code of 10. On the host system, we see the following.

$ cargo run --release --manifest-path ./exit-with-process/Cargo.toml
...
Exiting with code 10
$ echo $?
10

exit-with-exit-code

This example produces the exit code of 11. On the host system, we see the following.

$ cargo run --release --manifest-path ./exit-with-exit-code/Cargo.toml
...
Exiting with code 11
$ echo $?
11

Running with Wasmtime Runtimee

When compiling these two examples using the wasm32-wasip1 target, the use of std::process::exit produces the same exit code as the host binary, as expected. However, the use of std::process::ExitCode results in the exit code of 1, regardless of the value provided to ExitCode::from.

These expectations have been provided as a set of unit tests in src/lib.rs.

With Jest

With the just command runner, run the following

$ just test
cargo rustc --manifest-path exit-with-process/Cargo.toml --release --target
wasm32-wasip1 -- # -C lto=y -C panic=abort -C opt-level=z -C codegen-units=1
    Finished `release` profile [optimized] target(s) in 0.00s
cargo rustc --manifest-path exit-with-exit-code/Cargo.toml --release --target
wasm32-wasip1 -- # -C lto=y -C panic=abort -C opt-level=z -C codegen-units=1
    Finished `release` profile [optimized] target(s) in 0.00s
cargo test
    Finished `test` profile [unoptimized + debuginfo] target(s) in 0.14s
     Running unittests src/lib.rs
(target/debug/deps/wasm_wasi_return_code_reproducer-aed685ebe2675c4c)

running 3 tests
hello world
test tests::test_simple_wasm_return ... ok
Exiting with code 11`
Exiting with code 10
test tests::test_exit_with_exit_code ... FAILED
test tests::test_exit_with_process ... ok

failures:

---- tests::test_exit_with_exit_code stdout ----
thread 'tests::test_exit_with_exit_code' panicked at src/lib.rs:82:9:
assertion `left == right` failed
  left: 11
 right: 1
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace


failures:
    tests::test_exit_with_exit_code

test result: FAILED. 2 passed; 1 failed; 0 ignored; 0 measured; 0 filtered out;
finished in 0.57s

error: test failed, to rerun pass `--lib`
error: Recipe `test` failed on line 19 with exit code 101

Without Just

Without just, the following will compile the two examples to wasm with wasm32-wasip1:

$ cargo rustc \
        --manifest-path $BIN_NAME/Cargo.toml \
        --release \
        --target wasm32-wasip1 \
        -- \
        -C panic=abort \
        -C opt-level=z \
        -C codegen-units=1

where $BIN_NAME is one of [exit-with-process, exit-with-exit-code].

The tests can be run using the standard cargo test.

Generated WASM

Looking at the WASM and decompiling it to WAT, we can see that in the ExitCode case, the main (marked as no_mangle) function is returning a i32.const 1:

(func $main (type 0) (result i32)
  (local i32)
  global.get $__stack_pointer
  ;; ...
  global.set $__stack_pointer
  i32.const 1)

System Notes

rustc versions: rustc 1.80.1 (3f5fd8dd4 2024-08-06), rustc 1.81.0 (eeb90cda1 2024-09-04), rustc 1.82.0-beta.3 (4976ae480 2024-09-09), and rustc 1.83.0-nightly (28e8f01c2 2024-09-17) host OS:

$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 22.04.4 LTS
Release:        22.04
Codename:       jammy