go程序启动时，runtime会自己创建一个channel并关闭吗？如果是，这个过程中都做了哪些工作呢？
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DarkPrince2
2021-05-22 16:55:09
第二课的作业，我在使用dlv调试关闭值为nil的chan时，在runtime.closechan处打断点，第一次运行到函数的地方，打印参数c的值不是nil，请问是go程序在启动时，会使用runtime自己创建一个chan并关闭吗？
以上调试的代码是：
[root@f0391391e8a2 sendtoNil]# cat -n send_to_nil.go
1 package main
2
3 func main() {
4 var ch chan int
5 close(ch)
6 ch <- 1
7 }
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Xargin
2021-05-22
[root@0783a24aec92 home]# dlv debug ch.go Type 'help' for list of commands. (dlv) b closechan Breakpoint 1 (enabled) set at 0x404b03 for runtime.closechan() /usr/local/go/src/runtime/chan.go:340 (dlv) c > runtime.closechan() /usr/local/go/src/runtime/chan.go:340 (hits goroutine(1):1 total:1) (PC: 0x404b03) Warning: debugging optimized function 335: src := sg.elem 336: typeBitsBulkBarrier(t, uintptr(dst), uintptr(src), t.size) 337: memmove(dst, src, t.size) 338: } 339: => 340: func closechan(c *hchan) { 341: if c == nil { 342: panic(plainError("close of nil channel")) 343: } 344: 345: lock(&c.lock) (dlv) bt 0 0x0000000000404b03 in runtime.closechan at /usr/local/go/src/runtime/chan.go:340 1 0x0000000000430b74 in runtime.main at /usr/local/go/src/runtime/proc.go:192 2 0x000000000045b7c1 in runtime.goexit at /usr/local/go/src/runtime/asm_amd64.s:1373 (dlv) frame 1 > runtime.closechan() /usr/local/go/src/runtime/chan.go:340 (hits goroutine(1):1 total:1) (PC: 0x404b03) Warning: debugging optimized function Frame 1: /usr/local/go/src/runtime/proc.go:192 (PC: 430b74) 187: cgocall(_cgo_notify_runtime_init_done, nil) 188: } 189: 190: doInit(&main_inittask) 191: => 192: close(main_init_done) 193: 194: needUnlock = false 195: unlockOSThread() 196: 197: if isarchive || islibrary { (dlv) l Goroutine 1 frame 1 at /usr/local/go/src/runtime/proc.go:192 (PC: 0x430b74) 187: cgocall(_cgo_notify_runtime_init_done, nil) 188: } 189: 190: doInit(&main_inittask) 191: => 192: close(main_init_done) 193: 194: needUnlock = false 195: unlockOSThread() 196: 197: if isarchive || islibrary { (dlv) frame 0 > runtime.closechan() /usr/local/go/src/runtime/chan.go:340 (hits goroutine(1):1 total:1) (PC: 0x404b03) Warning: debugging optimized function Frame 0: /usr/local/go/src/runtime/chan.go:340 (PC: 404b03) 335: src := sg.elem 336: typeBitsBulkBarrier(t, uintptr(dst), uintptr(src), t.size) 337: memmove(dst, src, t.size) 338: } 339: => 340: func closechan(c *hchan) { 341: if c == nil { 342: panic(plainError("close of nil channel")) 343: } 344: 345: lock(&c.lock) (dlv) bt 0 0x0000000000404b03 in runtime.closechan at /usr/local/go/src/runtime/chan.go:340 1 0x0000000000430b74 in runtime.main at /usr/local/go/src/runtime/proc.go:192 2 0x000000000045b7c1 in runtime.goexit at /usr/local/go/src/runtime/asm_amd64.s:1373 (dlv) c > runtime.closechan() /usr/local/go/src/runtime/chan.go:340 (hits goroutine(1):2 total:2) (PC: 0x404b03) Warning: debugging optimized function 335: src := sg.elem 336: typeBitsBulkBarrier(t, uintptr(dst), uintptr(src), t.size) 337: memmove(dst, src, t.size) 338: } 339: => 340: func closechan(c *hchan) { 341: if c == nil { 342: panic(plainError("close of nil channel")) 343: } 344: 345: lock(&c.lock) (dlv) bt 0 0x0000000000404b03 in runtime.closechan at /usr/local/go/src/runtime/chan.go:340 1 0x00000000004601c3 in main.main at ./ch.go:9 2 0x0000000000430ba8 in runtime.main at /usr/local/go/src/runtime/proc.go:203 3 0x000000000045b7c1 in runtime.goexit at /usr/local/go/src/runtime/asm_amd64.s:1373 (dlv)1h021-05-22
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