From: Alberto Bertogli <albertito@blitiri.com.ar>
Date: Fri, 6 Nov 2015 01:40:56 +0000 (+0000)
Subject: testing: only call flag.Parse if it has not been called before
X-Git-Tag: go1.6beta1~501
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=ab196aeff21bedd7acd0e38d74e77989255f1d3f;p=gostls13.git

testing: only call flag.Parse if it has not been called before

Calling flag.Parse twice can be problematic if other goroutines called
flag.Parsed in between: the race detector complains due to the
write after read from a different goroutine.

This can happen if TestMain calls flag.Parse and launches goroutines
that call flag.Parsed, for example if it initializes a server which
checks flags.

This patch makes testing.M.Run only parse the flags if they have not
been parsed already.

Change-Id: Id9f8c31c5f90614e3f34c63d1a32cf7e9055d68e
Reviewed-on: https://go-review.googlesource.com/16739
Reviewed-by: Russ Cox <rsc@golang.org>
---

diff --git a/src/testing/testing.go b/src/testing/testing.go
index 1dcc35ebc0..6237da9abd 100644
--- a/src/testing/testing.go
+++ b/src/testing/testing.go
@@ -485,7 +485,11 @@ func MainStart(matchString func(pat, str string) (bool, error), tests []Internal
 
 // Run runs the tests. It returns an exit code to pass to os.Exit.
 func (m *M) Run() int {
-	flag.Parse()
+	// TestMain may have already called flag.Parse.
+	if !flag.Parsed() {
+		flag.Parse()
+	}
+
 	parseCpuList()
 
 	before()