From: Rob Pike <r@golang.org>
Date: Tue, 5 May 2015 15:59:18 +0000 (-0700)
Subject: fmt: change the overflow test for large numbers in verbs
X-Git-Tag: go1.5beta1~748
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=92715d7780e1a7801c2d35069bc8bd86426429c4;p=gostls13.git

fmt: change the overflow test for large numbers in verbs

The old one was inferior.

Fixes #10695.

Change-Id: Ia7fb88c9ceb1b10197b77a54f729865385288d98
Reviewed-on: https://go-review.googlesource.com/9709
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
---

diff --git a/src/fmt/fmt_test.go b/src/fmt/fmt_test.go
index 5d3357004f..90112bb2a3 100644
--- a/src/fmt/fmt_test.go
+++ b/src/fmt/fmt_test.go
@@ -538,6 +538,7 @@ var fmtTests = []struct {
 	{"%T", nil, "<nil>"},
 	{"%-1", 100, "%!(NOVERB)%!(EXTRA int=100)"},
 	{"%017091901790959340919092959340919017929593813360", 0, "%!(NOVERB)%!(EXTRA int=0)"},
+	{"%184467440737095516170v", 0, "%!(NOVERB)%!(EXTRA int=0)"},
 
 	// The "<nil>" show up because maps are printed by
 	// first obtaining a list of keys and then looking up
diff --git a/src/fmt/print.go b/src/fmt/print.go
index 9c373145dd..1d8db0aac4 100644
--- a/src/fmt/print.go
+++ b/src/fmt/print.go
@@ -291,10 +291,12 @@ func parsenum(s string, start, end int) (num int, isnum bool, newi int) {
 		return 0, false, end
 	}
 	for newi = start; newi < end && '0' <= s[newi] && s[newi] <= '9'; newi++ {
-		num = num*10 + int(s[newi]-'0')
-		if num < 0 {
+		const maxInt32 = 1<<31 - 1 // 31 bits is plenty for a width.
+		max := maxInt32/10 - 1
+		if num > max {
 			return 0, false, end // Overflow; crazy long number most likely.
 		}
+		num = num*10 + int(s[newi]-'0')
 		isnum = true
 	}
 	return