[Buildroot] [PATCH] core/pkg-generic: fix instrumentation for packages that install nowhere

[Peter Korsgaard <peter@korsgaard.com>]

>>>>> "Yann" == Yann E MORIN <yann.morin.1998@free.fr> writes:

 > A (target [0]) package can independently declare installing in various
 > locations: target, staging, or images. The default is to only install
 > in target.

 > When a package opts out from installing to target, but does not opts
 > in to install in any other location, the package is not downloaded,
 > extracted, patched, configured, nor built at all. As a consequence, none
 > of the per-step instrumentation is not executed, specifically the
 > listing of files before/after the package sequence.

 > Down the line, the package infra does not cope well with that situation,
 > because the gathering-install step, the one that synchronises all the
 > optional target, staging, or images install steps, still gets run.

 > And as #13836 shows, this does not go well:

 >     /bin/sh: /home/tbuild/myboard/build/foo/.files-list.after: No such file or directory
 >     make[1]: *** [/home/tbuild/myboard/build/foo/.stamp_installed] Error 1
 >     make: *** [_all] Error 2

 > So, we should have ensured that the gathering-install step itself
 > depends on the build step, which would have solved the issue.

 > However, this bug really illustrates a more fundamental issue: does it
 > even make sense to have a package that installs nothing in any location?
 > Indeed, why even bother with that package to begin with if it will not
 > provide anything at all?

 > It turns out that yes, this makes sense. We have some packages, that
 > do not install anything at all, and do not even build anything; they are
 > there just to ensure that we can download something that will ultimately
 > be used by another package. This is the case for example for packages
 > that provide linux extensions, like aufs [1].

 > Additionally, some ugly out-of-tree packages could conceivably install
 > things during the build (or even configure!) steps. That's not unheard
 > of... [2]

 > So, the solution is to ensure that the gathering-install step does
 > depend on the build step, to trigger the proper dependency chain and
 > have the instrumentation hooks properly run even in that degenerate
 > case.

 > Fixes: #13836

 > [0] a host package can't opt out of installing anything.
 > [1] that one is actually missing AUFS_INSTALL_TARGET = NO, so this
 >     hides the issue.
 > [2] even us are not 100% clean on that topic: gcc will install files in
 >     staging and target as part of the same step (not the build, granted,
 >     but still...)

 > Reported-by: "Weber, Matthew L Collins" <Matthew.Weber@collins.com>
 > Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>
 > Cc: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

Committed to 2021.02.x and 2021.05.x, thanks.

-- 
Bye, Peter Korsgaard