The answer (like with virtually all questions like this on golang-nuts) is: Possibly, but you can not rely on it. Assuming that it is might break your program now or at a non-specific future date or on a non-specific current or future processor.
If you need atomic operations, please use the sync/atomic package. If you don't, your program is incorrect and go tooling will complain about it being incorrect. On Mon, Jan 9, 2017 at 2:46 PM, 陈诚 <ncu.br...@gmail.com> wrote: > Yes, I think you are right about the case in my sample code. The code > doesn't show exactly what I'm concerned about. I just wanna know whether a > write to a global pointer in 64-bit machine an atomic operation or not. > > 在 2017年1月9日星期一 UTC+8上午6:22:12，Caleb Doxsey写道： > >> Shouldn't this particular case be ok? From the memory doc: >> https://golang.org/ref/mem >> >> The go statement that starts a new goroutine happens before the >>> goroutine's execution begins. >> >> >> So the write has to happen before the goroutine starts. At least that's >> what the example indicates: >> >> >>> For example, in this program: >> >> >> >> var a string >> >> func f() { >> >> print(a) >> >> } >> >> func hello() { >> >> a = "hello, world" >> >> go f() >> >> } >> >> >> >>> calling hello will print "hello, world" at some point in the future >>> (perhaps after hello has returned). >> >> >> On Sunday, January 8, 2017 at 1:17:56 PM UTC-5, 陈诚 wrote: >> >>> Is the size of a pointer value 32 bits or 64 bits in golang when build >>> with `GOARCH=amd64` option specified and running on 64-bit OS? >>> If it's 64-bit size, is a global pointer value 8-byte aligned in memory >>> so that a read or write operation of that pointer value is carried out >>> atomically? >>> For example, in the following code, is it possible that the global >>> pointer p is only partially updated when the read goroutine read the >>> pointer? >>> var p *int >>> >>> void main() { >>> i := 1 >>> p = &i >>> go func() { fmt.Println(*p) } () >>> } >>> >>> The scenario I'm concerning is that there is only one write but multiple >>> reads on a global pointer value, and reading of an old value of the pointer >>> is not important. Thanks in advance! >>> >> -- > You received this message because you are subscribed to the Google Groups > "golang-nuts" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to golang-nuts+unsubscr...@googlegroups.com. > For more options, visit https://groups.google.com/d/optout. > -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. To unsubscribe from this group and stop receiving emails from it, send an email to golang-nuts+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
