Re: [PATCH] build: fix exporting for make 3.82

[Jan Beulich <jbeulich@xxxxxxxx>]

On 14.06.2022 17:40, Jan Beulich wrote:
> GNU make 3.82 apparently has a quirk where exporting an undefined
> variable prevents its value from subsequently being updated. This
> situation can arise due to our adding of -rR to MAKEFLAGS, which takes
> effect also on make simply re-invoking itself. Once these flags are in
> effect, CC (in particular) is empty (undefined), and would be defined
> only via Config.mk including StdGNU.mk or alike. With the quirk, CC
> remains empty, yet with an empty CC the compiler minimum version check
> fails, breaking the build.
> 
> Move the exporting of the various tool stack component variables past
> where they gain their (final) values.
> 
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
> ---
> There may be further factors playing into the described quirk, as I've
> also observed that simply running make as 2nd time would lead to
> successful building of xen/.

Albeit perhaps that's simply because then no re-invocation of make is
involved, as auto.conf and auto.conf.cmd then already exist (and are
up-to-date).

Jan

> While this wasn't a problem until several weeks back, I've not been able
> to identify which exact commit would have caused the breakage. Hence no
> Fixes: tag.
> 
> --- a/xen/Makefile
> +++ b/xen/Makefile
> @@ -44,8 +44,6 @@ export ARCH SRCARCH
>  # Allow someone to change their config file
>  export KCONFIG_CONFIG ?= .config
>  
> -export CC CXX LD NM OBJCOPY OBJDUMP ADDR2LINE
> -
>  export TARGET := xen
>  
>  .PHONY: dist
> @@ -244,6 +242,7 @@ export TARGET_ARCH     := $(shell echo $
>                                  -e s'/riscv.*/riscv/g')
>  
>  export CONFIG_SHELL := $(SHELL)
> +export CC CXX LD NM OBJCOPY OBJDUMP ADDR2LINE
>  export YACC = $(if $(BISON),$(BISON),bison)
>  export LEX = $(if $(FLEX),$(FLEX),flex)
>  
>