From: Rob Pike <r@golang.org>
Date: Thu, 12 Apr 2012 23:28:37 +0000 (+1000)
Subject: [release-branch.go1] fmt: fix crash of %b on huge negative int64
X-Git-Tag: go1.0.1~31
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=18a71beb07d845176fcab6711b766eeee4d35d46;p=gostls13.git

[release-branch.go1] fmt: fix crash of %b on huge negative int64

««« backport 344d5c33331a
fmt: fix crash of %b on huge negative int64
The buffer had 64 bytes but needs one more for the sign.

Fixes #3510.

R=golang-dev, dave, dsymonds
CC=golang-dev
https://golang.org/cl/6011057
»»»
---

diff --git a/src/pkg/fmt/fmt_test.go b/src/pkg/fmt/fmt_test.go
index 758fc50d08..de0342967c 100644
--- a/src/pkg/fmt/fmt_test.go
+++ b/src/pkg/fmt/fmt_test.go
@@ -461,6 +461,9 @@ var fmttests = []struct {
 	// zero reflect.Value, which formats as <nil>.
 	// This test is just to check that it shows the two NaNs at all.
 	{"%v", map[float64]int{math.NaN(): 1, math.NaN(): 2}, "map[NaN:<nil> NaN:<nil>]"},
+
+	// Used to crash because nByte didn't allow for a sign.
+	{"%b", int64(-1 << 63), "-1000000000000000000000000000000000000000000000000000000000000000"},
 }
 
 func TestSprintf(t *testing.T) {
diff --git a/src/pkg/fmt/format.go b/src/pkg/fmt/format.go
index 2186f334b9..caf900d5c3 100644
--- a/src/pkg/fmt/format.go
+++ b/src/pkg/fmt/format.go
@@ -10,7 +10,7 @@ import (
 )
 
 const (
-	nByte = 64
+	nByte = 65 // %b of an int64, plus a sign.
 
 	ldigits = "0123456789abcdef"
 	udigits = "0123456789ABCDEF"