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fmt: fix buffer underflow for negative integers 

Allow room for the initial minus sign of negative integers when
computing widths.

Fixes #10945.

Change-Id: I04d80203aaff64611992725d613ec13ed2ae721f
Reviewed-on: https://go-review.googlesource.com/10393
Reviewed-by: Rob Pike <r@golang.org>
This commit is contained in:
Håvard Haugen 2015-05-25 23:14:35 +02:00 committed by Rob Pike
parent 9378493d16
commit 70cf7352b4
2 changed files with 8 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
src/fmt/fmt_test.go
View File

@ -557,10 +557,11 @@ var fmtTests = []struct {
{"%0.100f", 1.0, zeroFill("1.", 100, "")},
{"%0.100f", -1.0, zeroFill("-1.", 100, "")},
// Used to panic: integer function didn't look at f.prec or f.unicode or f.width.
// Used to panic: integer function didn't look at f.prec, f.unicode, f.width or sign.
{"%#.80x", 42, "0x0000000000000000000000000000000000000000000000000000000000000000000000000000002a"},
{"%.80U", 42, "U+0000000000000000000000000000000000000000000000000000000000000000000000000000002A"},
{"%#.80U", '日', "U+000000000000000000000000000000000000000000000000000000000000000000000000000065E5 '日'"},
{"%.65d", -44, "-00000000000000000000000000000000000000000000000000000000000000044"},
{"%+.65d", 44, "+00000000000000000000000000000000000000000000000000000000000000044"},
{"% .65d", 44, " 00000000000000000000000000000000000000000000000000000000000000044"},
{"% +.65d", 44, "+00000000000000000000000000000000000000000000000000000000000000044"},

14
src/fmt/format.go
View File

@ -162,6 +162,11 @@ func (f *fmt) integer(a int64, base uint64, signedness bool, digits string) {
return
}
negative := signedness == signed && a < 0
if negative {
a = -a
}
var buf []byte = f.intbuf[0:]
if f.widPresent || f.precPresent || f.plus || f.space {
width := f.wid + f.prec // Only one will be set, both are positive; this provides the maximum.
@ -177,9 +182,7 @@ func (f *fmt) integer(a int64, base uint64, signedness bool, digits string) {
width += 1 + 1 + utf8.UTFMax + 1
}
}
if f.plus {
width++
} else if f.space {
if negative || f.plus || f.space {
width++
}
if width > nByte {
@ -188,11 +191,6 @@ func (f *fmt) integer(a int64, base uint64, signedness bool, digits string) {
}
}
negative := signedness == signed && a < 0
if negative {
a = -a
}
// two ways to ask for extra leading zero digits: %.3d or %03d.
// apparently the first cancels the second.
prec := 0