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// Copyright 2023 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
// #cgo noescape annotations for a C function means its arguments won't escape to heap.
// We assume that there won't be 100 new allocated heap objects in other places,
// i.e. runtime.ReadMemStats or other runtime background works.
// So, the tests are:
// 1. at least 100 new allocated heap objects after invoking withoutNoEscape 100 times.
// 2. less than 100 new allocated heap objects after invoking withoutNoEscape 100 times.
/*
// TODO(#56378): #cgo noescape runCWithNoEscape
void runCWithNoEscape(void *p) {
}
void runCWithoutNoEscape(void *p) {
}
*/
import "C"
import (
"fmt"
"runtime"
"runtime/debug"
"unsafe"
)
const num = 100
func init() {
register("CgoNoEscape", CgoNoEscape)
}
//go:noinline
func withNoEscape() {
var str string
C.runCWithNoEscape(unsafe.Pointer(&str))
}
//go:noinline
func withoutNoEscape() {
var str string
C.runCWithoutNoEscape(unsafe.Pointer(&str))
}
func CgoNoEscape() {
// make GC stop to see the heap objects allocated
debug.SetGCPercent(-1)
var stats runtime.MemStats
runtime.ReadMemStats(&stats)
preHeapObjects := stats.HeapObjects
for i := 0; i < num; i++ {
withNoEscape()
}
runtime.ReadMemStats(&stats)
nowHeapObjects := stats.HeapObjects
if nowHeapObjects-preHeapObjects >= num {
fmt.Printf("too many heap objects allocated, pre: %v, now: %v\n", preHeapObjects, nowHeapObjects)
}
runtime.ReadMemStats(&stats)
preHeapObjects = stats.HeapObjects
for i := 0; i < num; i++ {
withoutNoEscape()
}
runtime.ReadMemStats(&stats)
nowHeapObjects = stats.HeapObjects
if nowHeapObjects-preHeapObjects < num {
fmt.Printf("too few heap objects allocated, pre: %v, now: %v\n", preHeapObjects, nowHeapObjects)
}
fmt.Println("OK")
}
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