From 6a3b29895f72b62fd7c49d1d808ed1a8ab49fdc5 Mon Sep 17 00:00:00 2001
From: Russ Cox <rsc@golang.org>
Date: Wed, 20 Oct 2010 15:54:17 -0400
Subject: [PATCH] runtime: don't let select split stack

Fixes #1209.

R=ken2
CC=golang-dev
https://golang.org/cl/2612041
---
 src/pkg/runtime/chan.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/src/pkg/runtime/chan.c b/src/pkg/runtime/chan.c
index 436f8b1401b..d01159923fe 100644
--- a/src/pkg/runtime/chan.c
+++ b/src/pkg/runtime/chan.c
@@ -620,6 +620,12 @@ selunlock(Select *sel)
 }
 
 // selectgo(sel *byte);
+//
+// overwrites return pc on stack to signal which case of the select
+// to run, so cannot appear at the top of a split stack.
+// frame has 6 pointers and 4 int32 so 64 bytes max.
+// that's less than StackGuard-StackSmall, so okay.
+#pragma textflag 7
 void
 ·selectgo(Select *sel)
 {