From a07f6adda8663f86701356bca341112846ed251f Mon Sep 17 00:00:00 2001
From: David du Colombier <0intro@gmail.com>
Date: Wed, 9 Apr 2014 06:41:14 +0200
Subject: [PATCH] runtime: fix GOTRACEBACK on Plan 9

Getenv() should not call malloc when called from
gotraceback(). Instead, we return a static buffer
in this case, with enough room to hold the longest
value.

LGTM=rsc
R=rsc
CC=golang-codereviews
https://golang.org/cl/85680043
---
 src/pkg/runtime/env_plan9.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/src/pkg/runtime/env_plan9.c b/src/pkg/runtime/env_plan9.c
index 599319c7550..f732c9f294e 100644
--- a/src/pkg/runtime/env_plan9.c
+++ b/src/pkg/runtime/env_plan9.c
@@ -12,6 +12,7 @@ runtime·getenv(int8 *s)
 	intgo len;
 	byte file[128];
 	byte *p;
+	static byte b[128];
 
 	len = runtime·findnull((byte*)s);
 	if(len > sizeof file-6)
@@ -25,7 +26,14 @@ runtime·getenv(int8 *s)
 	if(fd < 0)
 		return nil;
 	n = runtime·seek(fd, 0, 2);
-	p = runtime·malloc(n+1);
+	if(runtime·strcmp((byte*)s, (byte*)"GOTRACEBACK") == 0){
+		// should not call malloc
+		if(n >= sizeof b)
+			return nil;
+		runtime·memclr(b, sizeof b);
+		p = b;
+	}else
+		p = runtime·malloc(n+1);
 	r = runtime·pread(fd, p, n, 0);
 	runtime·close(fd);
 	if(r < 0)