Commit 5db44c17 authored by Alberto Donizetti's avatar Alberto Donizetti Committed by Robert Griesemer

math/big: avoid panic in float.Text with negative prec

Fixes #15918

Change-Id: I4b434aed262960a2e6c659d4c2296fbf662c3a52
Reviewed-on: https://go-review.googlesource.com/23633
Run-TryBot: Robert Griesemer <gri@golang.org>
Reviewed-by: default avatarRobert Griesemer <gri@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
parent 77026ef9
......@@ -290,6 +290,11 @@ func TestFloat64Text(t *testing.T) {
// Issue 2625.
{383260575764816448, 'f', 0, "383260575764816448"},
{383260575764816448, 'g', -1, "3.8326057576481645e+17"},
// Issue 15918.
{1, 'f', -10, "1"},
{1, 'f', -11, "1"},
{1, 'f', -12, "1"},
} {
// The test cases are from the strconv package which tests float64 values.
// When formatting values with prec = -1 (shortest representation),
......
......@@ -41,8 +41,11 @@ import (
// x.Prec() mantissa bits.
// The prec value is ignored for the 'b' or 'p' format.
func (x *Float) Text(format byte, prec int) string {
const extra = 10 // TODO(gri) determine a good/better value here
return string(x.Append(make([]byte, 0, prec+extra), format, prec))
cap := 10 // TODO(gri) determine a good/better value here
if prec > 0 {
cap += prec
}
return string(x.Append(make([]byte, 0, cap), format, prec))
}
// String formats x like x.Text('g', 10).
......
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