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strconv: fix bug in extended-float based conversion.

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A test intended for denormals erroneously returned true also for
infinities, leading to bad overflows and wrong error estimates.

R=rsc
CC=golang-dev, remy
https://golang.org/cl/5489091
This commit is contained in:
Rémy Oudompheng 2011-12-22 17:28:35 -05:00 committed by Russ Cox
parent fc78c5aa00
commit 2afebbdf35
2 changed files with 5 additions and 2 deletions
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5
src/pkg/strconv/atof_test.go
View File

@ -114,6 +114,9 @@ var atoftests = []atofTest{
{"2.2250738585072012e-308", "2.2250738585072014e-308", nil}, {"2.2250738585072012e-308", "2.2250738585072014e-308", nil},
// http://www.exploringbinary.com/php-hangs-on-numeric-value-2-2250738585072011e-308/ // http://www.exploringbinary.com/php-hangs-on-numeric-value-2-2250738585072011e-308/
{"2.2250738585072011e-308", "2.225073858507201e-308", nil}, {"2.2250738585072011e-308", "2.225073858507201e-308", nil},
// A very large number (initially wrongly parsed by the fast algorithm).
{"4.630813248087435e+307", "4.630813248087435e+307", nil},
} }
type atofSimpleTest struct { type atofSimpleTest struct {
@ -200,7 +203,7 @@ func TestAtofRandom(t *testing.T) {
x, _ := ParseFloat(test.s, 64) x, _ := ParseFloat(test.s, 64)
switch { switch {
default: default:
t.Errorf("number %s badly parsed as %b (expected %b)", test.s, test.x, x) t.Errorf("number %s badly parsed as %b (expected %b)", test.s, x, test.x)
case x == test.x: case x == test.x:
case math.IsNaN(test.x) && math.IsNaN(x): case math.IsNaN(test.x) && math.IsNaN(x):
} }

2
src/pkg/strconv/extfloat.go
View File

@ -291,7 +291,7 @@ func (f *extFloat) AssignDecimal(d *decimal) (ok bool) {
const denormalExp = -1023 - 63 const denormalExp = -1023 - 63
flt := &float64info flt := &float64info
var extrabits uint var extrabits uint
if f.exp <= denormalExp || f.exp >= 1023-64 { if f.exp <= denormalExp {
extrabits = uint(63 - flt.mantbits + 1 + uint(denormalExp-f.exp)) extrabits = uint(63 - flt.mantbits + 1 + uint(denormalExp-f.exp))
} else { } else {
extrabits = uint(63 - flt.mantbits) extrabits = uint(63 - flt.mantbits)