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![David Chase](/assets/img/avatar_default.png)
This fixes a compile crash for GOEXPERIMENT=regabi,regabiargs go test -c go/constant Updates #40724. Change-Id: I238cef436e045647815326fc8fdb025c30ba1f5c Reviewed-on: https://go-review.googlesource.com/c/go/+/307309 Trust: David Chase <drchase@google.com> Run-TryBot: David Chase <drchase@google.com> TryBot-Result: Go Bot <gobot@golang.org> Reviewed-by: Cherry Zhang <cherryyz@google.com>
98 lines
2.1 KiB
Go
98 lines
2.1 KiB
Go
// run
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// Copyright 2021 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Excerpted from go/constant/value.go to capture a bug from there.
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package main
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import (
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"fmt"
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"math"
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"math/big"
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)
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type (
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unknownVal struct{}
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intVal struct{ val *big.Int } // Int values not representable as an int64
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ratVal struct{ val *big.Rat } // Float values representable as a fraction
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floatVal struct{ val *big.Float } // Float values not representable as a fraction
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complexVal struct{ re, im Value }
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)
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const prec = 512
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func (unknownVal) String() string { return "unknown" }
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func (x intVal) String() string { return x.val.String() }
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func (x ratVal) String() string { return rtof(x).String() }
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func (x floatVal) String() string {
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f := x.val
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// Use exact fmt formatting if in float64 range (common case):
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// proceed if f doesn't underflow to 0 or overflow to inf.
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if x, _ := f.Float64(); f.Sign() == 0 == (x == 0) && !math.IsInf(x, 0) {
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return fmt.Sprintf("%.6g", x)
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}
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return "OOPS"
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}
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func (x complexVal) String() string { return fmt.Sprintf("(%s + %si)", x.re, x.im) }
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func newFloat() *big.Float { return new(big.Float).SetPrec(prec) }
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//go:noinline
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//go:registerparams
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func itor(x intVal) ratVal { return ratVal{nil} }
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//go:noinline
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//go:registerparams
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func itof(x intVal) floatVal { return floatVal{nil} }
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func rtof(x ratVal) floatVal { return floatVal{newFloat().SetRat(x.val)} }
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type Value interface {
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String() string
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}
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//go:noinline
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//go:registerparams
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func ToFloat(x Value) Value {
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switch x := x.(type) {
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case intVal:
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if smallInt(x.val) {
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return itor(x)
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}
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return itof(x)
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case ratVal, floatVal:
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return x
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case complexVal:
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if Sign(x.im) == 0 {
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return ToFloat(x.re)
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}
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}
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return unknownVal{}
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}
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//go:noinline
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//go:registerparams
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func smallInt(x *big.Int) bool {
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return false
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}
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//go:noinline
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//go:registerparams
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func Sign(x Value) int {
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return 0
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}
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func main() {
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v := ratVal{big.NewRat(22,7)}
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s := ToFloat(v).String()
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fmt.Printf("s=%s\n", s)
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}
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