On Mon, Jul 11, 2016 at 3:49 AM, Manlio Perillo
<manlio.peri...@gmail.com> wrote:
> Il giorno domenica 10 luglio 2016 04:51:21 UTC+2, Ian Lance Taylor ha
> scritto:
>>
>> On Sat, Jul 9, 2016 at 4:38 PM, Erich Rickheit KSC <rick...@numachi.com>
>> wrote:
>> > I found myself writing code like this:
>> >
>> > s := make([]byte, len)
>> > for i := 0; i < len; i++ {
>> > // fill in s with stringy goodness
>> > }
>> > return string(s)
>> >
>> > Does this reuse the memory in s for the string, or does it allocate new
>> > memory and copy? Or does escape analysis swoop in and make that
>> > decision?
>>
>> This will normally allocate new memory for the string and copy over
>> the bytes. I believe that the compiler could optimize this case, but
>> as far as I know no Go compiler currently implements that
>> optimization.
>>
>
> Since the compiler can already tell that s does not escape the function,
> what is the additional complexity for this optimization?
Making sure that s is not modified after the conversion to string.
That could happen in fairly subtle ways even if the slice is known to
not escape, as in
s2 := append(s, 0)
str := string(s)
s2[0] = 1
Ian
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