在 Go 中哪些对象是默认完成的,它有哪些陷阱? [英] Which objects are finalized in Go by default and what are some of the pitfalls of it?
问题描述
函数runtime.SetFinalizer(x, f interface{})
将与 x
关联的终结器设置为 f
.
The function runtime.SetFinalizer(x, f interface{})
sets the finalizer associated with x
to f
.
什么类型的对象默认被终结?
What kind of objects are finalized by default?
默认完成这些对象会导致哪些意外陷阱?
What are some of the unintended pitfalls caused by having those objects finalized by default?
推荐答案
默认完成以下对象:
os.File
:文件对象被垃圾回收时自动关闭.
os.File
: The file is automatically closed when the object is garbage collected.
os.Process
:最终确定将释放与进程相关的任何资源.在 Unix 上,这是一个无操作.在 Windows 上,它关闭与进程关联的句柄.
os.Process
: Finalization will release any resources associated with the process. On Unix, this is a no-operation. On Windows, it closes the handle associated with the process.
在 Windows 上,包 net
可以自动关闭网络连接.
On Windows, it appears that package net
can automatically close a network connection.
Go 标准库没有为上述对象类型设置终结器.
The Go standard library is not setting a finalizer on object kinds other than the ones mentioned above.
在实际程序中似乎只有一个潜在的问题可能导致问题:当 os.File
完成时,它将调用操作系统以关闭文件描述符.如果 os.File
是通过调用函数创建的 os.NewFile(fd int, name string) *File
并且文件描述符也被另一个(不同的)使用os.File
,然后垃圾收集 either 文件对象之一将使另一个文件对象不可用.例如:
There seems to be only one potential issue that may cause problems in actual programs: When an os.File
is finalized, it will make a call to the OS to close the file descriptor. In case the os.File
has been created by calling function os.NewFile(fd int, name string) *File
and the file descriptor is also used by another (different) os.File
, then garbage collecting either one of the file objects will render the other file object unusable. For example:
package main
import (
"fmt"
"os"
"runtime"
)
func open() {
os.NewFile(1, "stdout")
}
func main() {
open()
// Force finalization of unreachable objects
_ = make([]byte, 1e7)
runtime.GC()
_, err := fmt.Println("some text") // Print something via os.Stdout
if err != nil {
fmt.Fprintln(os.Stderr, "could not print the text")
}
}
打印:
could not print the text
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