I would start by building it with inlining disabled and assembler output
enabled. Then compare the assembly code for main.A and main.B.
go build -gcflags 'all=-l -S' x.go 2>y
On Tue, Mar 19, 2024 at 1:12 PM Mohamad Rostami <mb.rostam...@gmail.com>
wrote:
> Well, I used runtime runtime.MemStats StackInuse.
> I don't have much knowledge about compiler optimization.
> But to make it clear for myself:
>
> considering these 2 functions:
>
> //go:noinline
> func A() {
> var h int
> for i := 0; i < 1e5; i++ {
> h = i
> _ = h
> fmt.Printf("%+v\n", &h)
> }
> }
>
> //go:noinline
> func B() {
> for i := 0; i < 1e5; i++ {
> h := i
> _ = h
> fmt.Printf("%+v\n", &h)
> }
> }
>
> The address of h in B is changing in each iteration although it's not
> causing stack to grow.
>
> If you point me to the documentation for this specific case, I would
> appreciate it.
> Regards,
>
> On Tuesday, March 19, 2024 at 5:46:36 PM UTC+1 Ian Lance Taylor wrote:
>
>> On Tue, Mar 19, 2024 at 9:36 AM Mohamad Rostami <mb.ros...@gmail.com>
>> wrote:
>> >
>> > I've seen in many places in go source code re-declaring a variable with
>> the same name.
>> > e.g:
>> > for i < j {
>> > h := ...
>> > }
>> > Instead of
>> > var h int
>> > for i < j {
>> > h = ...
>> > }
>> >
>> > So I did a benchmark to check the differences. I didn't find any
>> performance related differences, but in terms of Stack Memory in use, the
>> second approach is better than the first one.
>> >
>> > Not sure if the way is in standard library is by intention or something
>> that should be ignored.
>>
>> The two versions are basically equivalent. How are you measuring
>> stack memory usage? If they are different, there may be something to
>> fix in the compiler.
>>
>> Ian
>>
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