Hello, On antradienis 17 Lapkritis 2009 03:11:32 Joey Hess wrote: >> + # Now look for a more specific build system that is >> auto-buildable in + # both any previous and current steps. > >So says the comment, and the commit message, but not the code:
Now I see that this comment is confusing, I didn't express myself too well
here.
>> + for my $prevstep (BUILD_STEPS) {
>> + last if ($prevstep eq $step);
>> +
>> + # Find the first build system that is
>> auto-buildable in $prevstep. + for $system
>> (@buildsystems) {
>> + next unless defined $system;
>> + $system =
>> create_buildsystem_instance($system, @_) unless ref $system; +
>> if ($system->check_auto_buildable($prevstep)) { +
>> # If a candidate build system
>> is both more specific than the +
>> # base build system, and auto-buildable in current step, it's +
>> # the one we are looking for. +
>> if ($system->isa(ref $base) &&
>> $system->check_auto_buildable($step)) { +
>> return $system;
>
>This may return a system before it has tested every prior step in
>BUILD_STEPS
The idea was to get an auto-buildable match on any (i.e. a single, but not
all) prior step as well as current step. But that does not matter any more
because this method is based on the flaw you pointed out.
> This may return a system before it has tested every prior step in
> BUILD_STEPS.
>
> > + }
> > + else {
> > + # It's pointless to
> > consider this build system
once again
> > + $system = undef;
>
> BTW,
> This mutates @buildsystems via the binding established via the foreach.
> But that is a) too far above for that the be clear on first reading, and
> b) one of perl's absolute worst features for code maintainability, which
> I prefer to avoid.
Ok, I won't use this technique again.
> So, when cmake support was added to debhelper 7.3.0, the behavior of
> dh_auto_configure for such a package actually changed. In retrospect,
> then, we failed to get that right, and are only lucky that it seems to
> have broken nothing.
>
> It also means that if another build system is added to @BUILDSYSTEMS in
> the future, we again risk breakage, even if it is added after makefile.
This basically means that current check_auto_buildable() API has hit its
limits and was wrongly designed from the start. Fortunately, we can freely
change it as it does not concern 3rd party build systems.
I have a couple of thoughts how to solve this unfortunate problem. I'll try to
write code and post a patch later today. Hopefully, I get things right this
time, hrrr... This auto-selection thing is really so complicated...
--
Modestas Vainius <modes...@vainius.eu>
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