[go-nuts] Re: Is the following funciton always safe to convert a string to a slice?

[T L]

And is the runtime.KeepAlive call in the following program essential to 
keep the correctness?

package main

import (
    "fmt"
    "unsafe"
    "reflect"
    "runtime"
)

func main() {
    a := [6]byte{'G', 'o', 'o', 'g', 'l', 'e'}
    bs := []byte("Golang")
    hdr := (*reflect.SliceHeader)(unsafe.Pointer(&bs))
    hdr.Data = uintptr(unsafe.Pointer(&a))
    
    runtime.KeepAlive(&a) // Is this line essential here?
    
    hdr.Len = 2
    hdr.Cap = len(a)
    fmt.Printf("%s\n", bs) // Go
    bs = bs[:cap(bs)]
    fmt.Printf("%s\n", bs) // Google
}

On Tuesday, April 21, 2020 at 9:48:08 AM UTC-4, T L wrote:
>
> func String2ByteSlice(str string) (bs []byte) {
>     strHdr := (*reflect.StringHeader)(unsafe.Pointer(&str))
>     sliceHdr := (*reflect.SliceHeader)(unsafe.Pointer(&bs))
>     
>     // Is it possible that the str value is allocated on stack
>     // and the stack grows at this moment, so the address value
>     // stored in strHdr.Data will become obsoleted?
>     
>     sliceHdr.Data = strHdr.Data
>     sliceHdr.Len = strHdr.Len
>     sliceHdr.Cap = strHdr.Len
>     
>     runtime.KeepAlive(&str)
>     
>     return
> }
>
>

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