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

[Adhemerval Zanella]

On 11/07/2017 15:23, Zack Weinberg wrote:
> On Tue, Jul 11, 2017 at 1:56 PM, Adhemerval Zanella
> <adhemerval.zanella@linaro.org> wrote:
>> Ping (x2). I think something we won't bother to emulate solaris behaviour,
>> so in a short we should document it and close it.
> 
> I agree that existing behavior should not be changed, but the text you
> proposed for the manual doesn't make a lot of sense unless you already
> know what the problem is.
> 
>>>> +On Linux the stack information return on @code{uc_stack} is empty by
>>>> +default.  It also the case for signal handling information through
>>>> +@code{sigaction} with @code{SA_SIGINFO}.  It could be obtained using
>>>> +architecture specific field from @code{uc_mcontext} member.
> 
> @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.
> 
> The detail regarding 'sigaction' belongs in the documentation for
> 'sigaction', and we currently don't document SA_SIGINFO at all, so I
> would just leave that bit out.

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.