Re: [PATCH] build: tweak variable exporting for make 3.82

[Anthony PERARD <anthony.perard@xxxxxxxxxx>]

On Fri, Jun 26, 2020 at 05:02:30PM +0200, Jan Beulich wrote:
> While I've been running into an issue here only because of an additional
> local change I'm carrying, to be able to override just the compiler in
> $(XEN_ROOT)/.config (rather than the whole tool chain), in
> config/StdGNU.mk:
> 
> ifeq ($(filter-out default undefined,$(origin CC)),)
> 
> I'd like to propose to nevertheless correct the underlying issue:
> Exporting an unset variable changes its origin from "undefined" to
> "file". This comes into effect because of our adding of -rR to
> MAKEFLAGS, which make 3.82 wrongly applies also upon re-invoking itself
> after having updated auto.conf{,.cmd}.
> 
> Move the export statement past $(XEN_ROOT)/config/$(XEN_OS).mk inclusion
> such that the variables already have their designated values at that
> point, while retaining their initial origin up to the point they get
> defined.
> 
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
> 
> --- a/xen/Makefile
> +++ b/xen/Makefile
> @@ -17,8 +17,6 @@ export XEN_BUILD_HOST       ?= $(shell hostnam
>  PYTHON_INTERPRETER   := $(word 1,$(shell which python3 python python2 
> 2>/dev/null) python)
>  export PYTHON                ?= $(PYTHON_INTERPRETER)
>  
> -export CC CXX LD
> -
>  export BASEDIR := $(CURDIR)
>  export XEN_ROOT := $(BASEDIR)/..
>  
> @@ -42,6 +40,8 @@ export TARGET_ARCH     := $(shell echo $
>  # Allow someone to change their config file
>  export KCONFIG_CONFIG ?= .config
>  
> +export CC CXX LD
> +
>  .PHONY: default
>  default: build

That patch is fine and it is probably better to export a variable that
has a value rather than before the variable is set.

Reviewed-by: Anthony PERARD <anthony.perard@xxxxxxxxxx>

Thanks,

-- 
Anthony PERARD