Re: [PATCH] selftests: Fix build failures when invoked from kselftest target

[Michael Ellerman <mpe@ellerman.id.au>]

On Fri, 2015-03-13 at 19:45 -0600, Shuah Khan wrote:
> Several tests that rely on implicit build rules fail to build,
> when invoked from the main Makefile kselftest target. These
> failures are due to --no-builtin-rules and --no-builtin-variables
> options set in the inherited MAKEFLAGS.
> 
> --no-builtin-rules eliminates the use of built-in implicit rules
> and --no-builtin-variables is for not defining built-in variables.
> These two options override the use of implicit rules resulting in
> build failures. In addition, inherited LDFLAGS result in build
> failures and there is no need to define LDFLAGS.  Clear LDFLAGS
> and MAKEFLAG when make is invoked from the main Makefile kselftest
> target. Fixing this at selftests Makefile avoids changing the main
> Makefile and keeps this change self contained at selftests level.
> 
> Signed-off-by: Shuah Khan <shuahkh@osg.samsung.com>
> ---
>  tools/testing/selftests/Makefile | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/tools/testing/selftests/Makefile b/tools/testing/selftests/Makefile
> index 4e51122..8e09db7 100644
> --- a/tools/testing/selftests/Makefile
> +++ b/tools/testing/selftests/Makefile
> @@ -22,6 +22,15 @@ TARGETS += vm
>  TARGETS_HOTPLUG = cpu-hotplug
>  TARGETS_HOTPLUG += memory-hotplug
>  
> +# Clear LDFLAGS and MAKEFLAGS if called from main
> +# Makefile to avoid test build failures when test
> +# Makefile doesn't have explicit build rules.
> +ifeq (1,$(MAKELEVEL))
> +undefine LDFLAGS
> +override define MAKEFLAGS =
> +endef
> +endif

You shouldn't need to use define/endef here, that is just for multi-line
variables.

This should be equivalent:

  ifeq (1,$(MAKELEVEL))
  undefine LDFLAGS
  override MAKEFLAGS =
  endif

cheers