From bf9fe659a93388e7f62320786160b74446768c0e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Uwe=20Kr=C3=BCger?=
 <45282134+UweKrueger@users.noreply.github.com>
Date: Fri, 9 Apr 2021 22:40:35 +0200
Subject: [PATCH] sync: fix `chan.close()` while a sending thread is waiting
 (#9654)

---
 vlib/sync/channel_close_test.v | 37 +++++++++++++++++++++++++++++++++-
 vlib/sync/channels.v           |  3 +++
 2 files changed, 39 insertions(+), 1 deletion(-)

diff --git a/vlib/sync/channel_close_test.v b/vlib/sync/channel_close_test.v
index 07ce9a90eb..ba5070e2e4 100644
--- a/vlib/sync/channel_close_test.v
+++ b/vlib/sync/channel_close_test.v
@@ -1,4 +1,4 @@
-import sync
+import time
 
 fn do_rec(ch chan int, resch chan i64) {
 	mut sum := i64(0)
@@ -71,3 +71,38 @@ fn test_channel_close_unbuffered() {
 	sum += <-resch
 	assert sum == i64(8000) * (8000 - 1) / 2
 }
+
+fn test_channel_send_close_buffered() {
+	ch := chan int{cap: 1}
+	t := go fn (ch chan int) {
+		ch <- 31
+		mut x := 45
+		ch <- 17 or {
+			x = -133
+		}
+		assert x == -133
+	}(ch)
+	time.sleep(100 * time.millisecond)
+	ch.close()
+	mut r := <-ch
+	r = <-ch or { 23 }
+	assert r == 23
+	t.wait()
+}
+
+fn test_channel_send_close_unbuffered() {
+	time.sleep(1 * time.second)
+	ch := chan int{}
+	t := go fn (ch chan int) {
+		mut x := 31
+		ch <- 177 or {
+			x = -71
+		}
+		assert x == -71
+	}(ch)
+	time.sleep(100 * time.millisecond)
+	ch.close()
+	r := <-ch or { 238 }
+	assert r == 238
+	t.wait()
+}
diff --git a/vlib/sync/channels.v b/vlib/sync/channels.v
index bae6526fcd..70b17491f0 100644
--- a/vlib/sync/channels.v
+++ b/vlib/sync/channels.v
@@ -165,6 +165,9 @@ pub fn (mut ch Channel) close() {
 	}
 	C.atomic_store_u16(&ch.write_sub_mtx, u16(0))
 	ch.writesem.post()
+	if ch.cap == 0 {
+		C.atomic_store_ptr(&ch.read_adr, voidptr(0))
+	}
 	ch.writesem_im.post()
 }