Windows: Fix build error incompatible pointer types

[daipom]

On GitHub workflows, building the native extensions for cool.io fails as follows:

../libev/ev.c: In function 'evpipe_write':
../libev/ev.c:2484:19: error: assignment to 'char *' from incompatible pointer
type 'WSABUF *' [-Wincompatible-pointer-types]
 2484 |           buf.buf = &buf;
      |                   ^

• Runner: windows-2022 (20240421.1.0)
• Use ruby/setup-ruby v1 to set up Ruby
  • https://github.com/actions/setup-ruby
• Dependency: cool.io v1.8.0

I have tested this by enabling Windows CI on my fork.
You can see this error occurs on Windows:

• https://github.com/daipom/cool.io/actions/runs/9060771058

In addition, I have made the test repository that depends on cool.io.
You can check this error here too:

• https://github.com/daipom/Test-Windows-CI-For-Ruby/actions/runs/9059543449

About this fix

The type of buf member of WSABUF is char *:

• https://learn.microsoft.com/en-us/windows/win32/api/ws2def/ns-ws2def-wsabuf

On libev upstream, this was already fixed on v4.25:

http://cvs.schmorp.de/libev/ev.c?r1=1.484&r2=1.485&pathrev=rel-4_25

Maybe we should try to update the overall libev version, but that could be difficult.
This PR intends to fix this error first.

Types of Changes

• Bug fix.

Contribution

• I added tests for my changes.
  • We can check this change by enabling Windows CI. So, I have included it in this PR.
  • Without this fix, the CI on Windows fails: https://github.com/daipom/cool.io/actions/runs/9060771058
  • With this fix, it succeeds: https://github.com/daipom/cool.io/actions/runs/9060821025
• I tested my changes locally.
  • I can't reproduce this error on my local, but we can confirm this fix resolves the build error in the CI.
• I agree to the Developer's Certificate of Origin 1.1.

[daipom]

@ioquatix Could you please see this?

[daipom]

Thanks for your review!

[ioquatix]

I released it in version 1.8.1. Please let me know how you get on.

[daipom]

I released it in version 1.8.1. Please let me know how you get on.

Thanks! Sure!

[daipom]

@ioquatix I have confirmed this issue is completely resolved!
Thanks so much for your quick response!

[ioquatix]

Thanks for your pull request and additions to CI.