Re: [PATCH 1/2] bitbake: ensure -f causes dependent tasks to be re-run

[Richard Purdie <richard.purdie@linuxfoundation.org>]

On Wed, 2012-06-20 at 09:55 +0200, Björn Stenberg wrote:
> Paul Eggleton wrote:
> > So my assumption is -f is most often used for the purpose of manually
> > forcing a recompile after you have made modifications to the already
> > extracted source code under the workdir.
> 
> I agree with that.
> 
> My concern is based on the fact that people (including myself) don't
> fully know all the details of how bitbake works, and tend to make
> assumptions based on other build systems they know, such as simple
> Makefiles.
> 
> I think the fact that bitbake sometime works differently means we
> should be extra careful about not playing into devlelopers'
> assumptions. The bitbake option --force sounds rather similar to
> make's --always-make, especially when it is described as: "force run
> of specified cmd, regardless of stamp status". While a tangent, the
> --force parameter in standard unix utils like cp, mv, rm also matter.
> 
> If we were to call it something different instead, like -t/--taint,
> this would avoid some assumptions about its behaviour and make it more
> clear that the output will be different even if the input is the same.
> 
> Sure, it's not a major issue. But I'm fairly confident that if we keep
> the option name but change its behaviour, I am going to have to
> explain more than once to developers not following this list or the
> commit logs why -f does not do what they think (even though one can
> argue it never did). I'd rather they discover up front that -f is
> deprecated and that they should look up a new option instead.

We should be clear, its not a change in behaviour, its a bugfix for a
variety of nasty problems related to sstate. sstate needs to behave as
people would expect under a variety of circumstances and this change
only changes the interaction between sstate and the stamp files. This is
an area that is relatively new, we've found a nasty issue where sstate
files can become "corrupted" and we need to avoid that as it threatens
the integrity of the project.

I don't think renaming the option is a particularly good idea, that will
upset many user's fingers and mean we have to scrub the documents and in
itself will cause a ton of questions that need to be answered.

I would agree that the bitbake help text should be enhanced to make it
clear what this option does though. I do also think we need to raise
awareness of the change (which is why it was mentioned in yesterday's
meeting).

I appreciate we probably will get this question from time to time. We
(Yocto) are working on adding some kind of question/answer system (stack
overflow style) to the website btw, and this would make a good question
and answer on there! That would give us all a lightweight way to at
least answer the question.

Cheers,

Richard