Hi,
neither is *always* the case. One example of where no allocation is done is
when converting a []byte into a string to use as a map-index, as long as a)
it is done in one expression and b) the key doesn't have to be stored (i.e.
the access is read-only):
b := []byte{70,111,111}
m := make(map[string]int)
v := m[string(b)] // does not allocate
And as always, a conversion might end on the stack, if the compiler can
prove that the storage doesn't have to survive the call, e.g.
x := "Hello world"
os.Stdout.Write([]byte(x)) // does not escape
(note, that in this example, it's important that `os.Stdout` is an
`*os.File`, not just an `io.Writer`, so the compiler actually knows the
real function that is called).
But, in general, I think you can assume that such a conversion has to
allocate and I'd guess that in most cases, it needs to go on the heap. You
can use `-gcflags=-m` to see if a particular conversion allocates or not.
On Fri, Jan 29, 2021 at 1:55 PM xie cui <cuiwei...@gmail.com> wrote:
> I mean convert using
> s := "abcefg"
> b := []byte(s)
> s2 := string(b)
>
> not convert using some unsafe.Pointer trick.
>
> On Friday, January 29, 2021 at 8:51:57 PM UTC+8 xie cui wrote:
>
>> does convert string to []byte, and convert []byte to string alway alloc
>> new space, and the new space is in heap?
>> if it is not, please show some demo codes?
>>
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