[Buildroot] [PATCH] support/graph-depends: detect circular dependencies
Yann E. MORIN
yann.morin.1998 at free.fr
Sat Jan 23 22:31:12 UTC 2016
Thomas, All,
On 2016-01-23 23:21 +0100, Thomas Petazzoni spake thusly:
> On Sat, 23 Jan 2016 23:04:45 +0100, Yann E. MORIN wrote:
[--SNIP--]
> Isn't kconfig already detecting such situations ? It normally spits out
> a warning when you have a circular dep, no ?
No, because the ones I'm concerned with are optional dependencies:
libgtk2 and libgtk3 have an optional dependency on cups, like so;
ifeq ($(BR2_PKG_CUPS),y)
FOO_DEPENDENCIES += cups
endif
And this is not caught at the Kconfig level, because there is actually
no circular deps there.
> > +# This function will check that there is no loop in the dependency chain
> > +# As a side effect, it builds up the dependency cache.
> > +def check_circular_deps(deps):
> > + def recurse(pkg):
> > + if not pkg in list(deps.keys()):
> > + return
> > + chain.append(pkg)
> > + for p in deps[pkg]:
> > + if p in chain:
> > + sys.stderr.write("\nRecursion detected for : %s\n" % (p))
> > + while True:
> > + _p = chain.pop()
> > + sys.stderr.write("which is a dependency of: %s\n" % (_p))
> > + if p == _p:
> > + sys.exit(1)
> > + recurse(p)
> > + chain.pop()
> > +
> > + chain = []
> > + for pkg in list(deps.keys()):
> > + recurse(pkg)
>
> I am a bit worried about the algorithmic complexity of this new
> function. As you know, we had issues with other parts of graph-depends
> having a too high algorithmic complexity to handle large
> configurations, or configurations having specific patterns of
> dependencies.
>
> Have you measured the time impact of this new check on a very large
> configuration (like allyespackageconfig) ?
I have an allyespackageconfig with an recent toolchain so I get a lot
of packages, and I tweaked the config to disable a few to enable others.
And no, the speed impact is not measurable for me. I'll come up with
numbers (of course, when there's no loop!) a bit later.
Regards,
Yann E. MORIN.
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