[Bug 49378] New: kernel32.WriteFile with multi byte characters reports incorrect number of written bytes

[WineHQ Bugzilla]

https://bugs.winehq.org/show_bug.cgi?id=49378

Bug ID: 49378
           Summary: kernel32.WriteFile with multi byte characters reports
                    incorrect number of written bytes
           Product: Wine
           Version: 5.10
          Hardware: x86-64
                OS: Linux
            Status: UNCONFIRMED
          Severity: minor
          Priority: P2
         Component: kernel32
          Assignee: [e-mail]
          Reporter: [e-mail]
      Distribution: ---

Created attachment 67438
  --> https://bugs.winehq.org/attachment.cgi?id=67438
Wine test case to trigger the bug

Writing utf-8 multibyte characters to stdout using stdio led to uncovering this
bug. Attached test case is a simple way to trigger the underlying issue.

Minimal steps leading to issue:
1. Set console output to CP_UTF8
2. Use WriteFile with multibyte characters

Expect outcome:
WriteFile reports number of bytes written.

Actual outcome:
WriteFile reports number of characters written.

Other observations while writing test case:
I first run same test case using kernelbase.WriteFile. Base version seems to
behavior differently because my test case passed. I only then noticed the
important detail that there is multiple WriteFile entry points.