Re: document $at_status for use in RUN-IF-{PASS,FAIL} of AT_CHECK

[Eric Blake]

On 08/20/2010 10:51 PM, Ralf Wildenhues wrote:
> It would be nice if I could write:
>    AT_CHECK([command that may fail with status 63],
>             [], [], [],
>             [AT_CHECK([test $at_status -ne 63 || exit 77])])
>
> instead of:
>    AT_CHECK([command that may fail with status 63 || ]dnl
>             [ { test $? -eq 63&&  exit 77; }],
>             [], [], [])
>
> or even:
>    AT_CHECK([command that may fail with status 63 || ]dnl
>             [ { res=$?; test $res -eq 63&&  exit 77; exit $res }],
>             [], [], [])
>
> for mapping an exit status of 63 to a SKIP.  The second variant destroys
> the information of what value other than 0 or 63 the status had, the
> third is even uglier, the former nicely shows the status in the verbose
> log and works with Autoconf 2.59+ (at least).
>
> Would you accept a patch to document $at_status being usable in the
> RUN-IF-FAIL and RUN-IF-PASS arguments of AT_CHECK (including coverage
> of course)?

Sounds good to me, unless you like my alternate idea:

> If not, then we could think about using a 'stdout'-like special
> value for the STATUS argument to AT_CHECK that just captures $?,
> but IMVHO the status has sufficiently different semantics from
> output that I hope we don't need to go this way.

If we don't want to expose $at_status, then my idea on this front is 
that the user names their own variable:

AT_CHECK([command], [my_status], [], [],
         [AT_CHECK([test $my_status -ne 63 || exit 77])])

The heuristic is that if the status argument is 'ignore', empty, 
numeric, or non-literal (as detected by AS_LITERAL_IF, an example being 
$expected) it maintains current interpretation; otherwise, it is assumed 
to be a shell variable name to be assigned the exit status of the test.

However, while those alternate heuristics will allow us to avoid 
exposing $at_status, it seems like a lot of complexity in the 
autotest/general.m4 file, compared to just documenting a fixed name that 
is available without any extra user effort.

--
Eric Blake   address@hidden    +1-801-349-2682
Libvirt virtualization library http://libvirt.org