Re: [RFC PATCH 1/2] Makefile: Make HOSTCFLAGS and HOSTCXXFLAGS user modifyable

[Sam Ravnborg <sam@ravnborg.org>]

On Fri, Jun 20, 2014 at 11:31:28AM -0700, Markus Mayer wrote:
> In order to allow the user to pass extra arguments to the host
> compiler, we no longer overwrite the host compiler flags in the
> makefile, but append them to what was passed in.
> 
> Signed-off-by: Markus Mayer <markus.mayer@linaro.org>
> ---
>  Makefile | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/Makefile b/Makefile
> index 97b2861..5795eea 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -251,8 +251,8 @@ CONFIG_SHELL := $(shell if [ -x "$$BASH" ]; then echo $$BASH; \
>  
>  HOSTCC       = gcc
>  HOSTCXX      = g++
> -HOSTCFLAGS   = -Wall -Wmissing-prototypes -Wstrict-prototypes -O2 -fomit-frame-pointer
> -HOSTCXXFLAGS = -O2
> +HOSTCFLAGS   += -Wall -Wmissing-prototypes -Wstrict-prototypes -O2 -fomit-frame-pointer
> +HOSTCXXFLAGS += -O2
>  
>  ifeq ($(shell $(HOSTCC) -v 2>&1 | grep -c "clang version"), 1)
>  HOSTCFLAGS  += -Wno-unused-value -Wno-unused-parameter \

With this patch you can only override HOSTCFLAGS.
In many cases appending to the falgs is actually what you want.

Please take a look at how we have implemented it for the kernel with KCFLAGS.
And notice that this is also described in Documentation/kbuild

	Sam