mruby-io doesn't work in process started as Windows service

[kou]

#4968 added file descriptor check in IO#initialize.
It raises an exception at IO.open(0, "r") https://github.com/mruby/mruby/blob/master/mrbgems/mruby-io/mrblib/io.rb#L363 when a process is started as Windows service. Because a process started as Windows service doesn't have a valid standard input. fstat(0, buf) returns non-zero.

Here are solutions I think:

1. Don't check file descriptor for 0, 1 and 2.
2. Open an internal pipe for 0, 1 and 2 when they are invalid.

Which solution do you like?

I think that 1. is enough.

FYI: CRuby uses 2.: fill_standard_fds() https://github.com/ruby/ruby/blob/master/ruby.c#L2556-L2584

[matz]

I agree that (1) is sufficient. Could you prepare a pull-request? Or shall I work on it?

[kou]

OK. I'll do it.

[matz]

Hmm. Are you going to make a pull-request from the above commit? Or shall I merge it?

[kou]

Sorry for not sharing the status of the commit.
I don't have an environment that can reproduce this problem. I need to ask our customer to confirm the commit fixes this problem.
It'll be done in a few days.

But the patch is simple and it'll fix this problem. So we can merge it without waiting the confirmation. (I'll share the result of the confirmation later.)
I've opened #5119.

[kou]

We've confirmed that #5119 fixes this problem.

[matz]

Does this fix migw crash issue?

[kou]

I think that this is unrelated to the MinGW crash issue.
But I don't know why the issue was occurred and fixed...