英文:
difference between in recover when run goroutine in new func or not
问题
这段代码涉及到defer和recover，用于捕获运行时错误。
版本1：
func a() {
defer func() {
if r := recover(); r != nil {
fmt.Println(r)
}
}()
b()
}
func b() {
go fmt.Println([]string{}[2])
}
func main() {
a()
time.Sleep(1 * time.Second)
fmt.Println("end")
}
版本2（只有func b()发生了变化）：
func b() {
go func() {
fmt.Println([]string{}[2])
}()
}
运行版本1：
> go run /tmp/version1.go
runtime error: index out of range
end
运行版本2：
> go run /tmp/t.go
panic: runtime error: index out of range
goroutine 5 [running]:
main.b.func1()
/tmp/t.go:19 +0x109
created by main.b
/tmp/t.go:20 +0x2b
goroutine 1 [sleep]:
time.Sleep(0x3b9aca00)
/usr/local/go/src/runtime/time.go:59 +0xf9
main.main()
/tmp/t.go:25 +0x29
exit status 2
为什么看起来不同呢？如果有人能给我详细的解释，谢谢你。
英文:
It is about defer and recover, to catch runtime error.
version 1:
func a() {
defer func() {
if r := recover(); r != nil {
fmt.Println(r)
}
}()
b()
}
func b() {
go fmt.Println([]string{}[2])
}
func main() {
a()
time.Sleep(1 * time.Second)
fmt.Println("end")
}
Version 2 (Only func b() changed) :
func b() {
go func() {
fmt.Println([]string{}[2])
}()
}
difference
run version 1:
> go run /tmp/version1.go
runtime error: index out of range
end
and version 2:
> go run /tmp/t.go
panic: runtime error: index out of range
goroutine 5 [running]:
main.b.func1()
/tmp/t.go:19 +0x109
created by main.b
/tmp/t.go:20 +0x2b
goroutine 1 [sleep]:
time.Sleep(0x3b9aca00)
/usr/local/go/src/runtime/time.go:59 +0xf9
main.main()
/tmp/t.go:25 +0x29
exit status 2
why it looks different?
thank you if someone can give me the detail message.
答案1
得分: 4
在版本1中，你的panic发生在主goroutine中，因为在goroutine被生成之前，必须解析[]string{}[2]。
在调度函数之前，必须解析所有函数的参数，goroutine也不例外。
一个goroutine的工作原理基本上与任何其他函数调用相同，只是在为调用设置堆栈之后，它在单独的上下文（线程）中执行。
在你的第二个示例中，你调用了一个没有参数的函数，然后在该函数中发生了panic。由于goroutine中没有调用recover()，所以你看到了默认的panic处理程序。
defer/recover()只能捕获同一goroutine中的panic。
如果你在b的顶部添加defer/recover，你将能够捕获它并进行任何操作（例如：像你在#1中那样打印它）。
英文:
In version 1, your panic happens in the main goroutine because []string{}[2] must be resolved before the goroutine can be spawned.
All arguments to a function must be resolved before it gets dispatched, and goroutines are no different.
A goroutine works basically the same as any other function call except that after the stack is setup for the call, it executes in a separate context (thread).
in your second example, you are calling a function with no args and then in that function you are panicing. Since there is no call to recover() in the goroutine, you are seeing the default panic handler.
defer/recover() can only capture a panic within the same goroutine.
If you add a defer / recover to the top of b, you will be able to capture it and do whatever (ie: println it like you did in #1)
通过集体智慧和协作来改善编程学习和解决问题的方式。致力于成为全球开发者共同参与的知识库，让每个人都能够通过互相帮助和分享经验来进步。
评论