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master
test/fixedbugs/issue30041.go
63 строки
1 KB
Cherry Zhang
reflect: eliminate write barrier for copying result in callReflect
01 фев 2019, 22:23
01 фев 2019, 22:23
7e987b7
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// run // Copyright 2019 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. // Issue 30041: copying results of a reflect-generated // call on stack should not have write barrier. package main import ( "reflect" "runtime" "unsafe" ) var badPtr uintptr var sink []byte func init() { // Allocate large enough to use largeAlloc. b := make([]byte, 1<<16-1) sink = b // force heap allocation // Any space between the object and the end of page is invalid to point to. badPtr = uintptr(unsafe.Pointer(&b[len(b)-1])) + 1 } type ft func() *int var fn ft func rf([]reflect.Value) []reflect.Value { a := reflect.ValueOf((*int)(nil)) return []reflect.Value{a} } const N = 1000 func main() { fn = reflect.MakeFunc(reflect.TypeOf(fn), rf).Interface().(ft) // Keep running GC so the write barrier is on. go func() { for i := 0; i < N; i++ { runtime.GC() } }() var x [10]uintptr for i := range x { x[i] = badPtr } for i := 0; i < N; i++ { runtime.Gosched() use(x) // prepare bad pointers on stack fn() } } //go:noinline func use([10]uintptr) {}