[Buildroot] [PATCH 12/16 v3] core: handle .br-external in a make rule

[Yann E. MORIN <yann.morin.1998@free.fr>]

Thomas, All,

On 2016-08-27 22:16 +0200, Thomas Petazzoni spake thusly:
> On Sun, 17 Jul 2016 12:34:32 +0200, Yann E. MORIN wrote:
> 
> >  BR2_EXTERNAL_FILE = $(BASE_DIR)/.br-external
> >  -include $(BR2_EXTERNAL_FILE)

Here ^^^^

> > -ifeq ($(BR2_EXTERNAL),)
> > -  $(shell rm -f $(BR2_EXTERNAL_FILE))
> > -else
> > +ifneq ($(BR2_EXTERNAL),)
> >    _BR2_EXTERNAL = $(shell cd $(BR2_EXTERNAL) >/dev/null 2>&1 && pwd)
> >    ifeq ($(_BR2_EXTERNAL),)
> >      $(error BR2_EXTERNAL='$(BR2_EXTERNAL)' does not exist, relative to $(TOPDIR))
> >    endif
> >    override BR2_EXTERNAL := $(_BR2_EXTERNAL)
> > -  $(shell echo BR2_EXTERNAL ?= $(BR2_EXTERNAL) > $(BR2_EXTERNAL_FILE))
> >    ifneq ($(wildcard $(BR2_EXTERNAL)/external.id),)
> >      BR2_EXTERNAL_ID := $(shell cat $(BR2_EXTERNAL)/external.id 2>/dev/null)
> >      ifeq ($(BR2_EXTERNAL_ID),)
> > @@ -173,6 +167,11 @@ else
> >    BR2_EXTERNAL_MK = $(BR2_EXTERNAL)/external.mk
> >  endif
> >  
> > +# This needs to be *after* we compute BR_EXTERNAL, above.
> > +.PHONY: $(BR2_EXTERNAL_FILE)
> > +$(BR2_EXTERNAL_FILE):
> > +	@echo BR2_EXTERNAL ?= $(BR_EXTERNAL) >$@
> > +
> 
> I'm probably missing something, but where is this make target being
> "triggered" ?

When make encounters a -include directive, and the file to be included
is the target of a rule, then make will trigger the rule before including
the file, even if the rule is defined after the inclusion (make parses
makefiles in multiple passes).

Regards,
Yann E. MORIN.

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