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fmt: fix bug printing large zero-padded hexadecimal

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We forgot to include the width of "0x" when computing the crossover
from internal buffer to allocated buffer.
Also add a helper function to the test for formatting large zero-padded
test strings.

Fixes #6777.

R=golang-codereviews, iant
CC=golang-codereviews
https://golang.org/cl/50820043
This commit is contained in:
Rob Pike 2014-01-16 09:48:23 -08:00
parent ca9975a45e
commit fc908a0298
2 changed files with 46 additions and 10 deletions
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39
src/pkg/fmt/fmt_test.go
View File

@ -498,18 +498,18 @@ var fmtTests = []struct {
{"%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"},
{"%b", int64(-1 << 63), zeroFill("-1", 63, "")},
// Used to panic.
{"%0100d", 1, "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000001"},
{"%0100d", -1, "-000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000001"},
{"%0.100f", 1.0, "1.0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"},
{"%0.100f", -1.0, "-1.0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"},
{"%0100d", 1, zeroFill("", 100, "1")},
{"%0100d", -1, zeroFill("-", 99, "1")},
{"%0.100f", 1.0, zeroFill("1.", 100, "")},
{"%0.100f", -1.0, zeroFill("-1.", 100, "")},
// Zero padding floats used to put the minus sign in the middle.
{"%020f", -1.0, "-000000000001.000000"},
{"%20f", -1.0, " -1.000000"},
{"%0100f", -1.0, "-00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000001.000000"},
{"%0100f", -1.0, zeroFill("-", 99, "1.000000")},
// Complex fmt used to leave the plus flag set for future entries in the array
// causing +2+0i and +3+0i instead of 2+0i and 3+0i.
@ -518,6 +518,33 @@ var fmtTests = []struct {
// Incomplete format specification caused crash.
{"%.", 3, "%!.(int=3)"},
// Used to panic with out-of-bounds for very large numeric representations.
// nByte is set to handle one bit per uint64 in %b format, with a negative number.
// See issue 6777.
{"%#064x", 1, zeroFill("0x", 64, "1")},
{"%#064x", -1, zeroFill("-0x", 63, "1")},
{"%#064b", 1, zeroFill("", 64, "1")},
{"%#064b", -1, zeroFill("-", 63, "1")},
{"%#064o", 1, zeroFill("", 64, "1")},
{"%#064o", -1, zeroFill("-", 63, "1")},
{"%#064d", 1, zeroFill("", 64, "1")},
{"%#064d", -1, zeroFill("-", 63, "1")},
// Test that we handle the crossover above the size of uint64
{"%#072x", 1, zeroFill("0x", 72, "1")},
{"%#072x", -1, zeroFill("-0x", 71, "1")},
{"%#072b", 1, zeroFill("", 72, "1")},
{"%#072b", -1, zeroFill("-", 71, "1")},
{"%#072o", 1, zeroFill("", 72, "1")},
{"%#072o", -1, zeroFill("-", 71, "1")},
{"%#072d", 1, zeroFill("", 72, "1")},
{"%#072d", -1, zeroFill("-", 71, "1")},
}
// zeroFill generates zero-filled strings of the specified width. The length
// of the suffix (but not the prefix) is compensated for in the width calculation.
func zeroFill(prefix string, width int, suffix string) string {
return prefix + strings.Repeat("0", width-len(suffix)) + suffix
}
func TestSprintf(t *testing.T) {

15
src/pkg/fmt/format.go
View File

@ -10,7 +10,9 @@ import (
)
const (
nByte = 65 // %b of an int64, plus a sign.
// %b of an int64, plus a sign.
// Hex can add 0x and we handle it specially.
nByte = 65
ldigits = "0123456789abcdef"
udigits = "0123456789ABCDEF"
@ -160,9 +162,16 @@ func (f *fmt) integer(a int64, base uint64, signedness bool, digits string) {
}
var buf []byte = f.intbuf[0:]
if f.widPresent && f.wid > nByte {
if f.widPresent {
width := f.wid
if base == 16 && f.sharp {
// Also adds "0x".
width += 2
}
if width > nByte {
// We're going to need a bigger boat.
buf = make([]byte, f.wid)
buf = make([]byte, width)
}
}
negative := signedness == signed && a < 0