Re: [yocto] Switching between multiple DISTROs without "contamination"

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

On Wed, 2022-07-13 at 15:32 +0200, Nicolas Jeker wrote:
> Thanks Martin and Mike for your explanations and tips.
> 
> So, I've done a lot of testing today and it seems I simplified the
> example in my first email a bit too much. The example as-is works fine
> when switching DISTROs as far as I can tell. The problem only arises
> when wildcards are used.
> 
> Changing my initial example like this should trigger the behaviour I've
> initially described:
> 
> SRC_URI:append:mydistro-dev = " file://application-dbg.service"
> 
> do_install {
>     # ...snip...
>     # systemd service
>     install -d ${D}${systemd_system_unitdir}
>     install -m 0644 ${WORKDIR}/*.service ${D}${systemd_system_unitdir}
> }
> 
> do_install:append:mydistro-dev() {
>     # debug systemd services
>     install -d ${D}${systemd_system_unitdir}
>     install -m 0644 ${WORKDIR}/application-dbg.service
> ${D}${systemd_system_unitdir}
> }
> 
> Notice the *.service in do_install.
> 
> From my testing, this is how contamination happens:
> 
> 1) Build with 'DISTRO=mydistro bitbake application'. All tasks for the
> recipe are run and the directories in WORKDIR are populated, including
> the "application.service" file.
> 2) Build with 'DISTRO=mydistro-dev bitbake application'. do_unpack is
> rerun and places the additional "application-dbg.service" file in
> WORKDIR.
> 3) Switching back to 'mydistro' will get the recipe from sstate cache,
> which works fine.
> 4) Changing application.bb and rebuilding with 'DISTRO=mydistro bitbake
> application' reruns do_install (as expected). This leads to the
> packages do_install picking up the additional "application-dbg.service"
> file left behind by the invocation in step 2).
> 
> Mike, Martin: Do you remember in which cases you encountered problems
> when sharing the build directory?

This is unfortunately a known issue and is one reason I'd like to stop
recipes downloading files to WORKDIR. Sadly changing that to fix this
bug is very invasive and painful but I think we do need to do so
somehow.

Cheers,

Richard