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runtime: overwrite existing keys for mapassign_faststr variant

Fixes #45045

Change-Id: Ifcc7bd31591870446ce3e5127489a0b887d413f1
Reviewed-on: https://go-review.googlesource.com/c/go/+/305089
Trust: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Run-TryBot: Cuong Manh Le <cuong.manhle.vn@gmail.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
This commit is contained in:
Cuong Manh Le 2021-03-26 23:29:25 +07:00
parent 49dccf141f
commit 23ffb5b9ae
2 changed files with 54 additions and 0 deletions

View File

@ -255,6 +255,9 @@ bucketloop:
// already have a mapping for key. Update it.
inserti = i
insertb = b
// Overwrite existing key, so it can be garbage collected.
// The size is already guaranteed to be set correctly.
k.str = key.str
goto done
}
ovf := b.overflow(t)

View File

@ -0,0 +1,51 @@
// run
// Copyright 2021 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package main
import (
"reflect"
"runtime"
"unsafe"
)
func k(c chan string, val string) string {
b := make([]byte, 1000)
runtime.SetFinalizer(&b[0], func(*byte) {
c <- val
})
var s string
h := (*reflect.StringHeader)(unsafe.Pointer(&s))
h.Data = uintptr(unsafe.Pointer(&b[0]))
h.Len = len(b)
return s
}
func main() {
{
c := make(chan string, 2)
m := make(map[string]int)
m[k(c, "first")] = 0
m[k(c, "second")] = 0
runtime.GC()
if s := <-c; s != "first" {
panic("map[string], second key did not retain.")
}
runtime.KeepAlive(m)
}
{
c := make(chan string, 2)
m := make(map[[2]string]int)
m[[2]string{k(c, "first")}] = 0
m[[2]string{k(c, "second")}] = 0
runtime.GC()
if s := <-c; s != "first" {
panic("map[[2]string], second key did not retain.")
}
runtime.KeepAlive(m)
}
}