[Buildroot] Interesting circular dependency, how to solve?

[Yann E. MORIN <yann.morin.1998@free.fr>]

Thomas, Paul, All,

On 2016-07-07 18:33 +0200, Yann E. MORIN spake thusly:
> On 2016-07-06 17:56 +0200, Thomas Petazzoni spake thusly:
> > Today, Paul (in Cc) reported on IRC an interesting problem: on a
> > configuration with systemd enabled (and acting as udev provider),
> > pciutils would fail to build due to libudev.h being missing.
> > 
> > After some investigation, "make graph-depends" revealed the origin of
> > the problem: a very interesting circular dependency. Here is what make
> > graph-depends thinks of the situation:
> > 
> > Recursion detected for  : systemd
> > which is a dependency of: udev
> > which is a dependency of: pciutils
> > which is a dependency of: linux
> > which is a dependency of: cryptodev-linux
> > which is a dependency of: openssl
> > which is a dependency of: libcurl
> > which is a dependency of: systemd
> 
> Hmmm... make itself should have spit a warning of its own. However, I
> could not see a way to have make error out; it is a mere warning... :-(

Indeed it does catch it. But not until it is time for it to actuall
build openssl:

    make[1]: Circular /home/ymorin/dev/buildroot/O/build/openssl-1.0.2h/.stamp_configured <- cryptodev-linux dependency dropped.
    >>> openssl 1.0.2h Downloading

DAng. Why doesn't it detect it at the beginning of the build? And why
can't we tell make to consider it an error rather than a warning?

Damn... :-/

Regards,
Yann E. MORIN.

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