从goroutine返回价值会发生什么 [英] What happens to return value from goroutine

问题描述

有人可以给出从goroutine返回的澄清值。

Could someone please give clarification values returned from the goroutine. Does the returned value from the goroutine is getting stored on stake.

例子：

example :

// function getNumber returns the "int i" and we can't use this returned value
// because this function is invoked as goroutine.
// We know that, to communicate between main and goroutine one could
// use the channel ( chan <- i), but I am interested to know about
// the use of return i in goroutine. Is it possible to get/ use this 
// returned value.
func getNumber(i int) int {
    return i   
    }

func main() {

    for i:=0; i<10; i++ {
        go printNumber(i)
        }
    time.Sleep(5)
    }

我们是否应该尽量避免常规中的回报价值？

Should we try to avoid the return valued in go routine ?

推荐答案

快速查看程序集输出显示

A quick bit of looking at the assembly output shows

$ go build -gcflags -S z.go

getNumber（）函数确实将结果存储到堆栈中。

The getNumber() function does store its results to the stack

"".getNumber t=1 size=16 value=0 args=0x10 locals=0x0
    0x0000 00000 (z.go:5)   TEXT    "".getNumber+0(SB),4,$0-16
    0x0000 00000 (z.go:6)   MOVQ    "".i+8(FP),BX
    0x0005 00005 (z.go:6)   MOVQ    BX,"".~r1+16(FP)
    0x000a 00010 (z.go:6)   RET ,

所以当它从一个goroutine调用时，它会将其结果存储到堆栈中。然而，这是一个新的堆栈，它在goroutine结束时被销毁，因此不可能检索返回值。

So when it is called from a goroutine, it does store its results to the stack. However this is a new stack which is destroyed when the goroutine ends so there is no possibility of retrieving the return value.

"".main t=1 size=96 value=0 args=0x0 locals=0x18
    0x0000 00000 (z.go:9)   TEXT    "".main+0(SB),$24-0
    0x0000 00000 (z.go:9)   MOVQ    (TLS),CX
    0x0009 00009 (z.go:9)   CMPQ    SP,16(CX)
    0x000d 00013 (z.go:9)   JHI ,22
    0x000f 00015 (z.go:9)   CALL    ,runtime.morestack_noctxt(SB)
    0x0014 00020 (z.go:9)   JMP ,0
    0x0016 00022 (z.go:9)   SUBQ    $24,SP
    0x001a 00026 (z.go:10)  MOVQ    $0,AX
    0x001c 00028 (z.go:10)  CMPQ    AX,$10
    0x0020 00032 (z.go:10)  JGE $0,74
    0x0022 00034 (z.go:11)  MOVQ    AX,"".i+16(SP)
    0x0027 00039 (z.go:11)  MOVQ    AX,(SP)
    0x002b 00043 (z.go:11)  MOVQ    $"".getNumber·f+0(SB),CX
    0x0032 00050 (z.go:11)  PUSHQ   CX,
    0x0033 00051 (z.go:11)  PUSHQ   $16,
    0x0035 00053 (z.go:11)  PCDATA  $0,$0
    0x0035 00053 (z.go:11)  CALL    ,runtime.newproc(SB)
    0x003a 00058 (z.go:11)  POPQ    ,CX
    0x003b 00059 (z.go:11)  POPQ    ,CX
    0x003c 00060 (z.go:10)  MOVQ    "".i+16(SP),AX
    0x0041 00065 (z.go:10)  INCQ    ,AX
    0x0044 00068 (z.go:10)  NOP ,
    0x0044 00068 (z.go:10)  CMPQ    AX,$10
    0x0048 00072 (z.go:10)  JLT $0,34
    0x004a 00074 (z.go:13)  MOVQ    $5,(SP)
    0x0052 00082 (z.go:13)  PCDATA  $0,$0
    0x0052 00082 (z.go:13)  CALL    ,time.Sleep(SB)
    0x0057 00087 (z.go:14)  ADDQ    $24,SP
    0x005b 00091 (z.go:14)  RET ,

然而，没有办法检索这些结果。

However there is no way of retrieving these results.

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