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

[Adhemerval Zanella]

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.