add another set of tests to examine "return from _start"

[yamt]

a return from _start is an equivalent of proc_exit(0) and thus should terminate other threads.
at least it's what wasi-libc as of today assumes.

cf. #21

(venv) spacetanuki% python3 test-runner/wasi_test_runner.py -t ../wasi-threads/test/testsuite -r ~/git/toywasm/test/wasi-testsuite-adapter.py
Test wasi_threads_exit_nonmain_wasi passed
Test wasi_threads_exit_main_busy passed
Test wasi_threads_return_main_wasi passed
Test wasi_threads_return_main_wasi_read passed
Test wasi_threads_return_main_block passed
Test wasi_threads_exit_main_wasi passed
Test wasi_threads_return_main_busy passed
Test wasi_threads_exit_nonmain_busy passed
Test wasi_threads_spawn passed
Test wasi_threads_exit_main_block passed
Test wasi_threads_exit_nonmain_wasi_read passed
Test wasi_threads_exit_nonmain_block passed
Test wasi_threads_exit_main_wasi_read passed

===== Test results =====
Runtime: toywasm v28.0.0
Suite: WASI threads proposal
  Total: 13
  Passed:  13
  Failed:  0
  Skipped: 0

Test suites: 1 passed, 0 total
Tests:       13 passed, 0 total
(venv) spacetanuki%

[yamt]

@abrown @loganek ping

[loganek]

@yamt thanks a lot for the change, and really sorry for late review. I can see that return from _start is only equivalent to proc_exit if the return code is not 0 (https://github.com/WebAssembly/wasi-libc/blob/main/libc-bottom-half/crt/crt1-command.c#L51). Do you have any context about that?

[yamt]

I can see that return from _start is only equivalent to proc_exit if the return code is not 0 (https://github.com/WebAssembly/wasi-libc/blob/main/libc-bottom-half/crt/crt1-command.c#L51).

you can read the code as "if r != 0, we can replace proc_exit with a return"
if you want to return non-zero value, you need to use proc_exit explicitly.

Do you have any context about that?

see #21
this PR is the option b.

WebAssembly/wasi-libc#367 is option c.

[yamt]

@abrown @loganek ping (again)

[abrown]

@yamt, I'll take a look this week.

[loganek]

Those tests look fine to me. I think for those kind of tests it'd be good to extend wasi testsuite config file spec and implement WebAssembly/wasi-testsuite#42 so tests can be terminated gracefully on failure.