What does the content about unsafe.Poiner in the compiler section in Go 1.15 release notes?

T L

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Jun 12, 2020, 8:28:18 AM6/12/20

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Package unsafe's safety rules allow converting an unsafe.Pointer into uintptr when calling certain functions. Previously, in some cases, the compiler allowed multiple chained conversions (for example, syscall.Syscall(…, uintptr(uintptr(ptr)), …)). The compiler now requires exactly one conversion. Code that used multiple conversions should be updated to satisfy the safety rules.

I didn't find the difference from Go 1.14.

Axel Wagner

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Jun 12, 2020, 12:47:03 PM6/12/20

to T L, golang-nuts

AIUI: The safety rules haven't changed. How the compiler interprets them has. Previously, it interpreted them so as to allow multiple chained conversions. Now it doesn't.

On Fri, Jun 12, 2020 at 2:28 PM T L <tapi...@gmail.com> wrote:

Package unsafe's safety rules allow converting an unsafe.Pointer into uintptr when calling certain functions. Previously, in some cases, the compiler allowed multiple chained conversions (for example, syscall.Syscall(…, uintptr(uintptr(ptr)), …)). The compiler now requires exactly one conversion. Code that used multiple conversions should be updated to satisfy the safety rules.

I didn't find the difference from Go 1.14.

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Ian Lance Taylor

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Jun 12, 2020, 12:55:24 PM6/12/20

to Axel Wagner, T L, golang-nuts

On Fri, Jun 12, 2020 at 9:46 AM 'Axel Wagner' via golang-nuts
<golan...@googlegroups.com> wrote:
>
> AIUI: The safety rules haven't changed. How the compiler interprets them has. Previously, it interpreted them so as to allow multiple chained conversions. Now it doesn't.

Yes.

Ian

> On Fri, Jun 12, 2020 at 2:28 PM T L <tapi...@gmail.com> wrote:
>>
>>
>> Package unsafe's safety rules allow converting an unsafe.Pointer into uintptr when calling certain functions. Previously, in some cases, the compiler allowed multiple chained conversions (for example, syscall.Syscall(…, uintptr(uintptr(ptr)), …)). The compiler now requires exactly one conversion. Code that used multiple conversions should be updated to satisfy the safety rules.
>>
>>
>> I didn't find the difference from Go 1.14.
>>
>> --
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>
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T L

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Jun 12, 2020, 12:56:12 PM6/12/20

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Is "uintptr(uintptr(ptr))" a typo? Or are there any other multiple chained conversions examples?

On Friday, June 12, 2020 at 12:47:03 PM UTC-4, Axel Wagner wrote:

AIUI: The safety rules haven't changed. How the compiler interprets them has. Previously, it interpreted them so as to allow multiple chained conversions. Now it doesn't.

On Fri, Jun 12, 2020 at 2:28 PM T L <tapi...@gmail.com> wrote:

Package unsafe's safety rules allow converting an unsafe.Pointer into uintptr when calling certain functions. Previously, in some cases, the compiler allowed multiple chained conversions (for example, syscall.Syscall(…, uintptr(uintptr(ptr)), …)). The compiler now requires exactly one conversion. Code that used multiple conversions should be updated to satisfy the safety rules.

I didn't find the difference from Go 1.14.

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Ian Lance Taylor

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Jun 12, 2020, 1:02:30 PM6/12/20

to T L, golang-nuts

On Fri, Jun 12, 2020 at 9:56 AM T L <tapi...@gmail.com> wrote:
>
> Is "uintptr(uintptr(ptr))" a typo? Or are there any other multiple chained conversions examples?

That is not a typo. That is the case that worked in 1.14 and does not
work in 1.15.

Ian

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T L

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Jun 12, 2020, 1:08:26 PM6/12/20

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On Friday, June 12, 2020 at 1:02:30 PM UTC-4, Ian Lance Taylor wrote:

On Fri, Jun 12, 2020 at 9:56 AM T L <tapi...@gmail.com> wrote:
>
> Is "uintptr(uintptr(ptr))" a typo? Or are there any other multiple chained conversions examples?

That is not a typo. That is the case that worked in 1.14 and does not
work in 1.15.

Ian

So "uintptr(unsafe.Pointer(ptr))" also doesn't work now?

> On Friday, June 12, 2020 at 12:47:03 PM UTC-4, Axel Wagner wrote:
>>
>> AIUI: The safety rules haven't changed. How the compiler interprets them has. Previously, it interpreted them so as to allow multiple chained conversions. Now it doesn't.
>>
>> On Fri, Jun 12, 2020 at 2:28 PM T L <tapi...@gmail.com> wrote:
>>>
>>>
>>> Package unsafe's safety rules allow converting an unsafe.Pointer into uintptr when calling certain functions. Previously, in some cases, the compiler allowed multiple chained conversions (for example, syscall.Syscall(…, uintptr(uintptr(ptr)), …)). The compiler now requires exactly one conversion. Code that used multiple conversions should be updated to satisfy the safety rules.
>>>
>>>
>>> I didn't find the difference from Go 1.14.
>>>
>>> --
>>> You received this message because you are subscribed to the Google Groups "golang-nuts" group.
>>> To unsubscribe from this group and stop receiving emails from it, send an email to golan...@googlegroups.com.
>>> To view this discussion on the web visit https://groups.google.com/d/msgid/golang-nuts/0f62c576-a1f9-467e-b99c-42f01edaa452o%40googlegroups.com.
>
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Ian Lance Taylor

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Jun 12, 2020, 1:33:32 PM6/12/20

to T L, golang-nuts

On Fri, Jun 12, 2020 at 10:08 AM T L <tapi...@gmail.com> wrote:
>
> On Friday, June 12, 2020 at 1:02:30 PM UTC-4, Ian Lance Taylor wrote:
>>
>> On Fri, Jun 12, 2020 at 9:56 AM T L <tapi...@gmail.com> wrote:
>> >
>> > Is "uintptr(uintptr(ptr))" a typo? Or are there any other multiple chained conversions examples?
>>
>> That is not a typo. That is the case that worked in 1.14 and does not
>> work in 1.15.
>>
>> Ian
>>
>
> So "uintptr(unsafe.Pointer(ptr))" also doesn't work now?

No, that continues to work as before. Nobody has said anything about that case.

Again: the case that no longer works is uintptr(uintptr(ptr)).

Ian

>> > On Friday, June 12, 2020 at 12:47:03 PM UTC-4, Axel Wagner wrote:
>> >>
>> >> AIUI: The safety rules haven't changed. How the compiler interprets them has. Previously, it interpreted them so as to allow multiple chained conversions. Now it doesn't.
>> >>
>> >> On Fri, Jun 12, 2020 at 2:28 PM T L <tapi...@gmail.com> wrote:
>> >>>
>> >>>
>> >>> Package unsafe's safety rules allow converting an unsafe.Pointer into uintptr when calling certain functions. Previously, in some cases, the compiler allowed multiple chained conversions (for example, syscall.Syscall(…, uintptr(uintptr(ptr)), …)). The compiler now requires exactly one conversion. Code that used multiple conversions should be updated to satisfy the safety rules.
>> >>>
>> >>>
>> >>> I didn't find the difference from Go 1.14.
>> >>>
>> >>> --
>> >>> You received this message because you are subscribed to the Google Groups "golang-nuts" group.
>> >>> To unsubscribe from this group and stop receiving emails from it, send an email to golan...@googlegroups.com.
>> >>> To view this discussion on the web visit https://groups.google.com/d/msgid/golang-nuts/0f62c576-a1f9-467e-b99c-42f01edaa452o%40googlegroups.com.
>> >
>> > --
>> > You received this message because you are subscribed to the Google Groups "golang-nuts" group.
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>> > To view this discussion on the web visit https://groups.google.com/d/msgid/golang-nuts/6139806c-8937-4f71-97a0-eae51fecdb8co%40googlegroups.com.
>
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T L

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Jun 12, 2020, 10:34:28 PM6/12/20

to golang-nuts

On Friday, June 12, 2020 at 1:33:32 PM UTC-4, Ian Lance Taylor wrote:

On Fri, Jun 12, 2020 at 10:08 AM T L <tapi...@gmail.com> wrote:
>
> On Friday, June 12, 2020 at 1:02:30 PM UTC-4, Ian Lance Taylor wrote:
>>
>> On Fri, Jun 12, 2020 at 9:56 AM T L <tapi...@gmail.com> wrote:
>> >
>> > Is "uintptr(uintptr(ptr))" a typo? Or are there any other multiple chained conversions examples?
>>
>> That is not a typo. That is the case that worked in 1.14 and does not
>> work in 1.15.
>>
>> Ian
>>
>
> So "uintptr(unsafe.Pointer(ptr))" also doesn't work now?

No, that continues to work as before. Nobody has said anything about that case.

Again: the case that no longer works is uintptr(uintptr(ptr)).

Ian

Get it. Thanks both for the explanations.

>> > On Friday, June 12, 2020 at 12:47:03 PM UTC-4, Axel Wagner wrote:
>> >>
>> >> AIUI: The safety rules haven't changed. How the compiler interprets them has. Previously, it interpreted them so as to allow multiple chained conversions. Now it doesn't.
>> >>
>> >> On Fri, Jun 12, 2020 at 2:28 PM T L <tapi...@gmail.com> wrote:
>> >>>
>> >>>
>> >>> Package unsafe's safety rules allow converting an unsafe.Pointer into uintptr when calling certain functions. Previously, in some cases, the compiler allowed multiple chained conversions (for example, syscall.Syscall(…, uintptr(uintptr(ptr)), …)). The compiler now requires exactly one conversion. Code that used multiple conversions should be updated to satisfy the safety rules.
>> >>>
>> >>>
>> >>> I didn't find the difference from Go 1.14.
>> >>>
>> >>> --
>> >>> You received this message because you are subscribed to the Google Groups "golang-nuts" group.
>> >>> To unsubscribe from this group and stop receiving emails from it, send an email to golan...@googlegroups.com.
>> >>> To view this discussion on the web visit https://groups.google.com/d/msgid/golang-nuts/0f62c576-a1f9-467e-b99c-42f01edaa452o%40googlegroups.com.
>> >
>> > --
>> > You received this message because you are subscribed to the Google Groups "golang-nuts" group.
>> > To unsubscribe from this group and stop receiving emails from it, send an email to golan...@googlegroups.com.
>> > To view this discussion on the web visit https://groups.google.com/d/msgid/golang-nuts/6139806c-8937-4f71-97a0-eae51fecdb8co%40googlegroups.com.
>
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