[rfc][icedtea-web] spawning linux jvm in rust lunchers

[Alex Kashchenko]

On 10/09/2018 02:06 PM, Jiri Vanek wrote:
>
> [...]
> 
>>> Currenly its only purpose can be some stds observation, but it is unlikely rightful.
>>> It should die, and all lunching logs shoudl be closed. Any other logging should be in java
>>> competence.
>>
>> So current behaviour (exit after spawn) is the one currently intended.
> 
> Tbh, I dont know how inherited streams  if parent dies. AFAIK they persists, but maybe likely it can
> depend on environment and individual impelmentations?

Inherited stream is just a copy of a file descriptor (pointing to file 
or terminal), dead parent process won't do any harm.


>
> [...]
>
>>> Do you have some idea how to do the exec-like behaviour in rust?
>>
>> Assuming exec(1) [3] here (not exec(3) [4]), current behaviour (args passed though, stdstreams
>> inherited) looks close enough to exec to me. Additionally we can also wait for ITW to exit with
>> status() [2] and pass its exit code back to shell.
> 
> Only close enough. The " replaces the current process image with a new process image." is not
> achieved - pid changes.

Behaviour with a lingering launcher is the same as with "exec" for any 
practical purpose, isn't it:

1. args passed through

2. streams inherited

3. exit code passed back on exit

4. signals (likely only Ctrl+C matters here) are delivered to both 
parent (launcher) and child (JVM)


>
> [...]
>
>>> Attached is updated patch, but I think the spawn x exec-like should be decided now, and should be
>>> incorporated.
>>
>> Patch looks good to me, I guess "await for ITW to exit" and more stdstreams handling can be added
>> later.
> 
> I included the  "await for ITW to exit" as it seems to affect the trait.

Change looks good to me.


> I'm wondering, if
> https://doc.rust-lang.org/std/process/struct.Command.html#method.status
> do the same, as
> https://doc.rust-lang.org/std/process/struct.Child.html#method.wait
> (https://doc.rust-lang.org/src/std/process.rs.html#761-764)

Yes, it is the same, calls waitpid [1][2][3].


[1] 
https://github.com/rust-lang/rust/blob/ca63a4e4383f502cf541e0b0bc1c13541918103d/src/libstd/process.rs#L806
[2] 
https://github.com/rust-lang/rust/blob/ca63a4e4383f502cf541e0b0bc1c13541918103d/src/libstd/process.rs#L1246
[3] 
https://github.com/rust-lang/rust/blob/b7c6e8f1805cd8a4b0a1c1f22f17a89e9e2cea23/src/libstd/sys/unix/process/process_unix.rs#L385

-- 
-Alex