child_process: add 'overlapped' stdio flag

[tarruda]

The 'overlapped' value sets the UV_OVERLAPPED_PIPE libuv flag in the child process stdio.

Fixes: #29238

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• tests added
• documentation is changed or added
• commit message follows commit guidelines

[mscdex]

Why not just always set UV_OVERLAPPED_PIPE for 'pipe' instead? Are there any drawbacks/incompatibilities with that?

[tarruda]

Why not just always set UV_OVERLAPPED_PIPE for 'pipe' instead? Are there any drawbacks/incompatibilities with that?

Yes, it can possibly break existing programs that run child process that are not prepared for overlapped I/O: libuv/libuv#95 (comment)

[mscdex]

Ok, perhaps we can just shorten the name to 'overlapped' instead?

[tarruda]

Ok, perhaps we can just shorten the name to 'overlapped' instead?

Added a fixup. If this is acceptable I will squash and edit the commit message.

[mscdex]

Can you also add a test for this?

[tarruda]

Can you also add a test for this?

Do you have any suggestions on how I should proceed to testing this?

The new option simply activates the UV_OVERLAPPED_PIPE libuv flag, is there any existing test infrastructure to verify that the correct flags were passed by the new option? I couldn't find any reference to UV_CREATE_PIPE in the tests, so I imagine the answer is "no".

I suppose I could just add a functional test that verifies overlapped I/O on the child process, but that would probably be duplicating one of the libuv tests.

Also, the code path should be close to the one followed by the'pipe' value. Would it be enough to copy one of the 'pipe' tests but pass 'overlapped' instead?

[mscdex]

At the very least there should be a test that specifying 'overlapped' (via stdio: 'overlapped' or manually expanded out to stdio: ['overlapped', 'overlapped', 'overlapped']) does not throw an exception (since the code currently throws on unsupported modes).

Pending tests as mscdex mentioned.

[tarruda]

At the very least there should be a test that specifying 'overlapped' (via stdio: 'overlapped' or manually expanded out to stdio: ['overlapped', 'overlapped', 'overlapped']) does not throw an exception (since the code currently throws on unsupported modes).

👍

I also want to add a test that runs a C++ windows program that will not work if the stdio handles are not overlapped pipes.

[tarruda]

I've added "overlapped-checker", a program which is used to verify the FILE_FLAG_OVERLAPPED status from the child. The new test uses this program to verify that the flag is correctly passed.

[tarruda]

PR ready for final review.

[tarruda]

Thanks @aduh95 @joaocgreis @bnoordhuis for the help with this PR