From acfe2f2655ab25d52c4347783c4de99fa2daaf62 Mon Sep 17 00:00:00 2001
From: Samuel Williams <samuel.williams@oriontransfer.co.nz>
Date: Fri, 24 Dec 2021 23:11:02 +1300
Subject: [PATCH] Improvements to `rb_io_wait` return value handling and
 internal implementation. (#5340)

---
 include/ruby/fiber/scheduler.h |  2 +-
 io.c                           | 27 +++++++++++++++++++--------
 2 files changed, 20 insertions(+), 9 deletions(-)

diff --git a/include/ruby/fiber/scheduler.h b/include/ruby/fiber/scheduler.h
index a255a1a712..14e36ffb3a 100644
--- a/include/ruby/fiber/scheduler.h
+++ b/include/ruby/fiber/scheduler.h
@@ -205,7 +205,7 @@ VALUE rb_fiber_scheduler_unblock(VALUE scheduler, VALUE blocker, VALUE fiber);
  * this for instance switches to another fiber etc.
  *
  * The  "events" here  is a  Ruby level  integer, which  is an  OR-ed value  of
- * `IO::READABLE`, `IO::WRITable`, and `IO::PRIORITY`.
+ * `IO::READABLE`, `IO::WRITABLE`, and `IO::PRIORITY`.
  *
  * @param[in]  scheduler  Target scheduler.
  * @param[in]  io         An io object to wait.
diff --git a/io.c b/io.c
index ba8a632757..957d36aa22 100644
--- a/io.c
+++ b/io.c
@@ -500,15 +500,15 @@ rb_cloexec_fcntl_dupfd(int fd, int minfd)
 
 #if defined(_WIN32)
 #define WAIT_FD_IN_WIN32(fptr) \
-    (rb_w32_io_cancelable_p((fptr)->fd) ? 0 : RB_NUM2INT(rb_io_wait(fptr->self, RB_INT2NUM(RUBY_IO_READABLE), Qnil)))
+    (rb_w32_io_cancelable_p((fptr)->fd) ? Qnil : rb_io_wait(fptr->self, RB_INT2NUM(RUBY_IO_READABLE), Qnil))
 #else
 #define WAIT_FD_IN_WIN32(fptr)
 #endif
 
 #define READ_CHECK(fptr) do {\
     if (!READ_DATA_PENDING(fptr)) {\
-	WAIT_FD_IN_WIN32(fptr);\
-	rb_io_check_closed(fptr);\
+        WAIT_FD_IN_WIN32(fptr);\
+        rb_io_check_closed(fptr);\
     }\
 } while(0)
 
@@ -1323,10 +1323,9 @@ rb_io_wait(VALUE io, VALUE events, VALUE timeout)
     // Not sure if this is necessary:
     rb_io_check_closed(fptr);
 
-    if (ready > 0) {
+    if (ready) {
         return RB_INT2NUM(ready);
-    }
-    else {
+    } else {
         return Qfalse;
     }
 }
@@ -1490,13 +1489,25 @@ rb_io_maybe_wait(int error, VALUE io, VALUE events, VALUE timeout)
 int
 rb_io_maybe_wait_readable(int error, VALUE io, VALUE timeout)
 {
-    return RB_NUM2INT(rb_io_maybe_wait(error, io, RB_INT2NUM(RUBY_IO_READABLE), timeout));
+    VALUE result = rb_io_maybe_wait(error, io, RB_INT2NUM(RUBY_IO_READABLE), timeout);
+
+    if (RTEST(result)) {
+        return RB_NUM2INT(result);
+    } else {
+        return 0;
+    }
 }
 
 int
 rb_io_maybe_wait_writable(int error, VALUE io, VALUE timeout)
 {
-    return RB_NUM2INT(rb_io_maybe_wait(error, io, RB_INT2NUM(RUBY_IO_WRITABLE), timeout));
+    VALUE result = rb_io_maybe_wait(error, io, RB_INT2NUM(RUBY_IO_WRITABLE), timeout);
+
+    if (RTEST(result)) {
+        return RB_NUM2INT(result);
+    } else {
+        return 0;
+    }
 }
 
 static void