Re: [PATCH] bitbake: do not set CCACHE_DISABLE=0

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

On Sun, 2012-07-22 at 13:03 +0200, Enrico Scholz wrote:
> Richard Purdie
> <richard.purdie-hQyY1W1yCW8ekmWlsbkhG0B+6BGkLq7r@public.gmane.org>
> writes:
> 
> >> and requesting explicitly that user specifies
> >> 
> >>  | CCACHE_DISABLE[unexport] = "1"
> >> 
> >> in his .conf?  Sounds hacky and inconsistent and makes it impossible to
> >> set CCACHE_DISABLE by external environment.
> >
> > The idea is that anyone enabling ccache would inherit the bbclass.
> 
> afais, the ccache.bbclass class is for assigning and cleaning some
> (imho) strange CCACHE_DIR only which lowers efficiency significantly.
> 
> Normal ccache usage with a single CCACHE_DIR works fine (and much better)
> without this class.

There are the following concerns that others have raised over time:

a) That the central ccache directory in the user's homedir can get
filled very easily and this isn't something that most users expect.
b) There is reuse of that directory between different architectures
which isn't desired
c) That a clean of a recipe does not remove the ccache objects
d) That CCACHE_DIR might not exist when ccache is called raising errors
e) that ccache has bugs/risk but making it recipe specific alleviates
some of the risk/contamination issues

I neither claim these are good or bad reasons but they are all dealt
with by the class. Its a question of which issues you want to run into
and what behaviour you want. If you strongly dislike the way CCACHE_DIR
is set, that can be overridden.

Personally speaking, I dislike ccache and would love to just remove all
the code related to it and disable it for everyone. Yes, it has some
performance wins in some corner case situations but it is of marginal
utility IMO.

> > The above could therefore be simplified to a hard ??= 1
> 
> for what is the '??=' ?  The value does not matter so it makes no sense
> that the user can assign a value.

Ok, we can just use = there...

Cheers,

Richard