[Buildroot] CMake package requires out of source build

Alexander Dahl post at lespocky.de
Wed Feb 17 18:16:28 UTC 2021


Hello Matt,

On Wed, Feb 17, 2021 at 11:59:36AM -0500, mattwood2000 at gmail.com wrote:
> On Wed, Feb 17, 2021 at 10:52 AM Alexander Dahl <post at lespocky.de> wrote:
> > Just out of curiousity: why would you want to build in source anyways?
> > Why not build out of source as usually recommended and first class
> > supported by CMake?
> 
> I would prefer to build the source like a normal cmake package,
> however Amazon disallows building their SDK anywhere within the
> original source directory.  Normally, there should not be any issue
> with:
> 
> ./cmake_pkg_src
> ./cmake_pkg_src/buildroot-build // PKG_SUPPORTS_IN_SOURCE_BUILD = NO

Oh, my bad. Of course building in a subfolder "build" (or with another name like above) is
quite common with CMake. I usually don't do this, but that's of course
only my personal preference.

> But in this case there is a cmake rule that iterates over the entire
> source directory to check if the build directory is present:
> https://github.com/alexa/avs-device-sdk/blob/master/build/cmake/DisallowOutOfSourceBuilds.cmake

That makes no sense to me. In that script they link to
https://gitlab.kitware.com/cmake/community/-/wikis/FAQ#cmake-does-not-generate-a-make-distclean-target-why
but that only covers in source builds.

> Removing the rule from BuildDefaults.cmake gets around this issue.
> Also, the source builds perfectly fine this way.  I'm not sure why
> Amazon forces this.

Agreed. So why not patch 'build/BuildDefaults.cmake' like that and add
the patch to the buildroot package for that avs-device-sdk instead of
changing buildroot core?

Greets
Alex

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