[PATCH] manual: Document getcontext uc_stack value on Linux [BZ #759]

[Zack Weinberg]

On Tue, Aug 8, 2017 at 2:27 PM, Adhemerval Zanella
<adhemerval.zanella@linaro.org> wrote:
> On 11/07/2017 18:43, Adhemerval Zanella wrote:
>> On 11/07/2017 17:25, Zack Weinberg wrote:
>>> On Tue, Jul 11, 2017 at 2:28 PM, Adhemerval Zanella
>>> <adhemerval.zanella@linaro.org> wrote:
>>>>
>>>> Right, I do not have a preference here about the wording but I do think
>>>> we should at least document Linux behaviour (which originated the bug
>>>> report). What about:
>>>>
>>>> @strong{Compatibility Note:} Depending on the operating system,
>>>> information about the current context's stack may be in the
>>>> @code{uc_stack} field of @var{ucp}, or it may instead instead be in
>>>> architecture-specific subfields of the @code{uc_mcontext} field.
>>>> On Linux the current context's stack returned on @code{uc_stack}
>>>> is empty by default.
>>>
>>> I actually think we _shouldn't_ document Linux's behavior in this
>>> case.  Without a great deal more verbiage about how to write code that
>>> portably examines the result of getcontext, it's better to just say
>>> "this information could be in two different places" than "this
>>> information could be in two different places, and on system X it's in
>>> this one."  Good code has to be prepared to look in both places.  That
>>> is the best _short_ advice.
>>
>> Taking in consideration getcontext is deprecated and this is specific
>> implementation detail I think it is still worth to mention Linux behaviour
>> without the need of extending how to proper use this API (which should
>> not be used in newer programs anyway and in my experience the program
>> that still rely on such *context, libgo for instance, already have a
>> lot of hacks for different systems). The manual imho should mainly
>> document the current system supported and its idiosyncrasies.
>>
>
> Zack do you still think we should not document Linux behaviour? I
> understand your point that for document getcontext in a portable
> way it would require more explanation, but I think the goal here
> is just document this specific Linux difference for this deprecated
> symbol.

I would still prefer to just say

>>>> @strong{Compatibility Note:} Depending on the operating system,
>>>> information about the current context's stack may be in the
>>>> @code{uc_stack} field of @var{ucp}, or it may instead be in
>>>> architecture-specific subfields of the @code{uc_mcontext} field.

and no more.

zw