On Sunday, February 25, 2018 at 11:46:02 PM UTC-5, Rob 'Commander' Pike
wrote:
>
> No. As I said, there are no guarantees. As it says in
> https://golang.org/doc/go1compat:
>
>
> - Use of package unsafe. Packages that import unsafe
> <https://golang.org/pkg/unsafe/> may depend on internal properties of
> the Go implementation. We reserve the right to make changes to the
> implementation that may break such programs.
>
>
>
Will the 3 APIs and the unsafe.Pointer be always there?
Will the "sync/atomic" package get broken?
This atomic package imports unsafe.
>
>
> On Mon, Feb 26, 2018 at 1:15 PM, <di...@veryhaha.com <javascript:>> wrote:
>
>>
>>
>> On Sunday, February 25, 2018 at 7:38:22 PM UTC-5, Rob 'Commander' Pike
>> wrote:
>>>
>>> The main rule about unsafe is that your program might work or might not.
>>> There are no guarantees either way. That's why it's called 'unsafe' and why
>>> you shouldn't use it. Your program that 'works' today could break tomorrow.
>>>
>>
>> ok, but, is there always an unsafe alternative/variant existing later?
>>
>>
>>>
>>> -rob
>>>
>>>
>>> On Mon, Feb 26, 2018 at 4:43 AM, Marvin Renich <mr...@renich.org> wrote:
>>>
>>>> * di...@veryhaha.com <di...@veryhaha.com> [180225 11:37]:
>>>> > I think I get it.
>>>> > Because the above program tries to modify the constant (or program)
>>>> zone,
>>>> > which is not allowed.
>>>> > The following program works:
>>>>
>>>> But, note that the language spec does not guarantee it to work. The
>>>> compiler is free to recognize what that first line is doing and optimize
>>>> the assignment into a string in a R/O memory segment. The optimization
>>>> is legal because the compiler does not have to recognize the use of
>>>> unsafe to determine the programmer's intent to subvert the type system.
>>>>
>>>> > package main
>>>> >
>>>> > import "fmt"
>>>> > import "unsafe"
>>>> > import "reflect"
>>>> >
>>>> > func main() {
>>>> > s := string([]byte{'k', 'e', 'e', 'p'})
>>>> > hdr := (*reflect.StringHeader)(unsafe.Pointer(&s))
>>>> > byteSequence := (*byte)(unsafe.Pointer(hdr.Data))
>>>> > fmt.Println(string(*byteSequence)) // k
>>>> > *byteSequence = 'j' // crash here
>>>> > fmt.Println(s) // expect: jeep
>>>> > }
>>>>
>>>> ...Marvin
>>>>
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>>>
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>
>
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