On Wednesday, March 22, 2017 at 9:29:32 PM UTC+8, Ian Lance Taylor wrote:
>
> On Wed, Mar 22, 2017 at 3:59 AM, T L <tapi...@gmail.com <javascript:>>
> wrote:
> >
> > On Wednesday, March 22, 2017 at 6:40:53 PM UTC+8, Jesse McNelis wrote:
> >>
> >> On Wed, Mar 22, 2017 at 8:51 PM, T L <tapi...@gmail.com> wrote:
> >> >
> >> > More accurately, I think it should be: from the POV of a programmer,
> >> > it's
> >> > globals, and things reachable from each goroutine.
> >> >
> >>
> >> The only way to reach a value is through a variable in scope and the
> >> only variables in scope are global or on the stack.
> >>
> >> 'heap pointers of local allocated memory blocks' are stored where ever
> >> you put them, but you can only put them in places you can find by
> >> using global or local stack variables.
> >
> >
> > So for this simple program:
> >
> > func main() {
> > var a int
> > go func() { // new goroutine
> > a++
> > }()
> >
> > // ...
> > }
> >
> > a will be allocated on heap.
> > a is referenced by both stack of main and the new goroutine?
> > how is it referenced, the pointer of a's memory block is stored in both
> > stacks?
>
> The pointer to a's memory is accessible from the stack of both
> goroutines. Otherwise the goroutines could not possibly refer to a.
>
> All usable memory must be reachable from global variables or from
> local variables on goroutine stacks. There is nothing else in Go.
> The runtime data structures mentioned earlier in the thread are just
> specific global variables.
>
> When we say that a local variable lives on the heap, what that really
> means is that the local variable of type T is replaced by a local
> variable of type *T, the normal zero-initialization of the local
> variable is replaced by new(T), and all references to the variable are
> changed to use an additional indirection.
>
> Ian
>
Thanks for the confirmation and extended explanation!
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