From 9eb19a02aea2f867972d2c28cab25e5df162091f Mon Sep 17 00:00:00 2001
From: "NARUSE, Yui" <naruse@airemix.jp>
Date: Thu, 15 Dec 2022 00:14:00 +0900
Subject: Add more comments why CRuby uses __pioinfo

---
 win32/win32.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

(limited to 'win32')

diff --git a/win32/win32.c b/win32/win32.c
index 1a532c6c7c..36335f144f 100644
--- a/win32/win32.c
+++ b/win32/win32.c
@@ -2584,6 +2584,18 @@ set_pioinfo_extra(void)
 #  define UCRTBASE "ucrtbase.dll"
 # endif
     /* get __pioinfo addr with _isatty */
+    /*
+     * Why Ruby depends to _pioinfo is
+     * * to associate socket and fd: CRuby creates fd with dummy file handle
+     *   and set socket to emulate Unix-like behavior. Without __pioinfo
+     *   we need something which manages the fd number allocation
+     * * to implement overlapped I/O for Windows 2000/XP
+     * * to emulate fcntl(2)
+     *
+     * see also
+     * * https://bugs.ruby-lang.org/issues/11118
+     * * https://bugs.ruby-lang.org/issues/18605
+     */
     char *p = (char*)get_proc_address(UCRTBASE, "_isatty", NULL);
     char *pend = p;
     /* _osfile(fh) & FDEV */
-- 
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