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Implement low-level (OS\) subprocess API #176

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fredemmott opened this issue Dec 16, 2021 · 1 comment
Open
1 of 10 tasks

Implement low-level (OS\) subprocess API #176

fredemmott opened this issue Dec 16, 2021 · 1 comment

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@fredemmott
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fredemmott commented Dec 16, 2021 •
edited by Atry

  • finalize signature of OS\posix_spawn() and OS\posix_spawnp()
  • (in progress, fred) add _OS\dup()
  • add _OS\waitpid_async() or similar
  • add _OS\shutdown()
  • add public APIs:
    • OS\posix_spawn() and OS\posix_spawnp()
    • OS\waitpid_async()
    • OS\shutdown()
    • OS\dup()
    • OS\socketpair() (already in _OS\)
@fredemmott
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add _OS\waitpid_async() or similar

Ideally, I'd want to add _OS\waitid_async(), and expose it as OS\waitid_async() and OS\waitpid_async() - however, waitid() does not exist in macos, despite being part of the specifications for some time.

I think we'd want to just add waitpid_async(), and if later we want process group support, we add _OS\waitpgid_async(), and add an OS\waitid_async() that wraps the two separate functions - unless MacOS adds waitid in the mean time.

... but the design of process group support can be left for later, that's just be brain dumping. For now, let's stick with just waitpid.

facebook-github-bot pushed a commit to facebook/hhvm that referenced this issue Mar 21, 2022
@fredemmott @facebook-github-bot
add HH\Lib\_Private\_OS\dup()
ac00a11 
Summary:
refs hhvm/hsl#176

This part of enabling a pattern of:
```
list($stderr_parent, $stderr_child) = OS\socketpair(); // yep, stderr is read-write
$stdin_child = OS\dup($stderr_child);
OS\shutdown($stdin_child, OS\SHUT_WR);
$stdout_child = OS\dup($stderr_child);
OS\shutdown($stdout_child, OS\SHUT_RD);
```

`dup2()` is not necessary as we support explicitly remapping FDs when creating subprocesses

`dup2()` is not desirable as:
- Hack programs do not have insights to the real FD numbers. Especially in CLI server mode, STDIN/STDOUT/STDERR may not be on the canonical STDIN_FILENO/STDOUT_FILENO/STDERR_FILENO
- Given that, there's a large risk of accidentally creating cross-request issues with `dup2()`

Reviewed By: shayne-fletcher

Differential Revision: D33166096

fbshipit-source-id: 41339a9a33c854982009086f3efdfc35277715c0
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@fredemmott