Implement proc_raise

[nullpo-head]

Signed-off-by: Takaya Saeki takaya@tetrate.io

[codefromthecrypt]

thanks for the straw man. I think this is best decoupled from OS handling especially what is supported by what OS is out of scope for us especially in documenting the WASI part.

Here's the suggestion:

add this type to the public wasi package, documenting that it is for proc_raise

type SignalHandler func(sig uint32) wasi.Errno

Add a default impl which only handles the exit signal and calls exit 1

ex.

var defaultSignalHandler SignalHandler = func(sig uint32) wasi.Errno {
   if exit or kill ... panic(wasi.ExitCode(exitCode))
}

add an option to override SignalHandler

Implement a built-in one for the current process, which I guess is only viable for Wasm-only processes. implement and cast the signals as syscall.Signal() and map go error to an errno
ex.

type currentPidSignalHandler { process}
func CurrentPidSignalHandler() (SignalHandler, err) {
// lookup process or fail
   return &currentPidSignalHandler{process}
}

// implementation is mainly just calling process.Signal

This allows unit tests to be easy as you can override SignalHandler. Also you can stick with cursory tests for the CurrentPidSignalHandler() for example, only testing when the OS isn't windows for now. What Go supports is out of scope and if someone wants to kill a process on windows we can ask and re-use code from func-e at that point.

[codefromthecrypt]

ps only add the SignalHandler type to the public wasi package.. the others leave internal. Of course similar to other things holes will need to be punched in wazero.WASIConfig

[codefromthecrypt]

Looks like we need to implement #293 and handle at least sigabrt (for AssemblyScript) and whatever grain ends up calling. Process exit is deprioritized as current use cases don't affect the host process. In fact, we can probably drop that entirely as no-one asked for it and stick with module or maybe also store scope. This focuses the pull review on code needed and leaves the gnarly os.Signal stuff out of it

[nullpo-head]

As discussed in #271 (comment), proc_raise is no longer necessary. I close this draft PR.