[Buildroot] [PATCH 1 of 7] infra: consistently use double dollar signs inside inner-xxx-targets

[Thomas De Schampheleire]

Hi Yann,

First of all: thanks a lot for the review!

On Sun, May 11, 2014 at 10:38 PM, Yann E. MORIN <yann.morin.1998 at free.fr> wrote:
> Thomas, All,
>
> On 2014-05-11 17:38 +0200, Thomas De Schampheleire spake thusly:
>> The inner-xxx-targets in the buildroot package infrastructures are
>> evaluated using $(eval) which causes variable references to be a bit
>> different than in regular make code. As we want most references to be
>> expanded only at the time of the $(eval) we should not use standard
>> references $(VAR) but rather use double dollar signs $$(VAR). This includes
>> function references like $(call), $(subst), etc. The only exception is the
>> reference to numbered variables, which are paremeters to the inner block:
>> $(1), $(2), etc.
>>
>> This patch introduces consistent usage of double-dollar signs throughout the
>> different inner-xxx-targets blocks.
> [--SNIP--]
>> diff --git a/package/pkg-autotools.mk b/package/pkg-autotools.mk
>> --- a/package/pkg-autotools.mk
>> +++ b/package/pkg-autotools.mk
>
> Did you forget that one, or did you leave it out on purpose:
>
> 46: AUTOCONF_AC_CHECK_FILE_VAL = ac_cv_file_$(subst -,_,$(subst /,_,$(subst .,_,$(1))))

This is not inside inner-xxx-targets. Moreover, it is used with
$(call), not $(eval) so there is no need for the double dollar signs.

>
> [--SNIP--]
>> @@ -201,7 +204,7 @@ endif
>>  #
>>  define AUTORECONF_HOOK
>>       @$$(call MESSAGE,"Autoreconfiguring")
>> -     $(Q)cd $$($$(PKG)_SRCDIR) && $(AUTORECONF) $$($$(PKG)_AUTORECONF_OPT)
>> +     $(Q)cd $$($$(PKG)_SRCDIR) && $$(AUTORECONF) $$($$(PKG)_AUTORECONF_OPT)
>
> You left out the $(Q) as-is. Although I agreee it's not very important
> and would still work (heck it already work as-is), I think we should
> cahnge it, for consistency sake, no?

Yes, I will change it to avoid any confusion about the rules.

>
> [--SNIP--]
>
> I see you have not changed anything in pkg-download.mk. Do you thinks
> there is nothing worth changing in there?
>
> I'm especialy thinking about these functions:
>
>     {DOWNLOAD,SOURCE_CHECK,SHOW_EXTERNAL_DEPS}_{GIT,BZR,CVS,SVN,SCP,HG,WGET,LOCALFILES}
>
> as well as: DOWNLOAD and DOWNLOAD_INNER

These functions are not eval'ed but call'ed. According to me, the
double dollars are not correct there.

Following your comment, I searched for the use of eval throughout
buildroot (filtering out the already known cases of generic, cmake,
autotools etc., and found following addition references:

docs/manual/manual.mk (GENDOC)
fs/*  (ROOTFS_TARGET)
package/pkg-utils.mk (caseconvert-helper)

I will update these blocks too in v2.

>
> [--SNIP--]
>> diff --git a/package/pkg-generic.mk b/package/pkg-generic.mk
>> --- a/package/pkg-generic.mk
>> +++ b/package/pkg-generic.mk
>
> You've left out the hook functions:
>     step_start
>     step_end
>     step_user
>
> and potentially:
>     step_time

These are all called using $(call) from a place that is outside of
inner-xxx-targets.
As far as I understand, double dollar signs are not needed (and will
not work) here.
For example, adding following line in step_start:

@echo Step start $(1) TOPDIR=$(TOPDIR) TOPDIR2=$$(TOPDIR)

will cause TOPDIR2 to be passed to the shell as $(TOPDIR) which gives:

/bin/bash: TOPDIR: command not found
Step start configure TOPDIR=/home/tdescham/repo/contrib/buildroot-misc TOPDIR2=

>
>> @@ -548,7 +550,7 @@ endif
>>  $$($(2)_TARGET_RSYNC_SOURCE):                SRCDIR=$$($(2)_OVERRIDE_SRCDIR)
>>  $$($(2)_TARGET_RSYNC_SOURCE):                PKG=$(2)
>>  $$($(2)_TARGET_PATCH):                       PKG=$(2)
>> -$$($(2)_TARGET_PATCH):                       RAWNAME=$(patsubst host-%,%,$(1))
>> +$$($(2)_TARGET_PATCH):                       RAWNAME=$$(patsubst host-%,%,$(1))
>>  $$($(2)_TARGET_PATCH):                       PKGDIR=$(pkgdir)
>
> Why not change the call to pkgdir ?

Because it does not work for pkgdir nor pkgname. These have to have a
single dollar sign.
I should update the comment in the next patch to reflect this.

>
>>  $$($(2)_TARGET_EXTRACT):             PKG=$(2)
>>  $$($(2)_TARGET_SOURCE):                      PKG=$(2)
>> @@ -559,9 +561,9 @@ endif
>>  # kernel case, the bootloaders case, and the normal packages case.
>>  ifeq ($(1),linux)
>>  $(2)_KCONFIG_VAR = BR2_LINUX_KERNEL
>> -else ifneq ($(filter boot/%,$(pkgdir)),)
>> +else ifneq ($$(filter boot/%,$(pkgdir)),)
>
> Ditto pkgdir.
>
>>  $(2)_KCONFIG_VAR = BR2_TARGET_$(2)
>> -else ifneq ($(filter toolchain/%,$(pkgdir)),)
>> +else ifneq ($$(filter toolchain/%,$(pkgdir)),)
>
> Ditto pkgdir.
>
> [--SNIP--]
>
> No change required in pkg-utils.mk either?
>
> For example, caseconvert-helper is $(eval)-ed.

True, I will fix in v2.
The other places in pkg-utils are not eval'ed.

>
> Also, in none of the xxx-package or host-xxx-package macros, you did
> double-$ the calls to pkgname or UPPERACSE. Is that a missing piece, or
> is taht on purpose?

I should indeed add double dollars on the uppercase call, but not on
pkgname as that doesn't work.

>
> Note: all my questions are just to make sure we did not miss anything.
> I'm genuinely asking if it is needed or not. This is a complex topic,
> and I'm unsure we've covered all the bases here. Maybe I'm just being a
> bit over-paranoid... ;-)

Not at all. Your questions are all valid and very useful! This is
exactly what code review is for...

>
> And, thank you for looking into this horrid mess that are Makefile
> functions! ;-)

Once and then never again ;-)

Best regards,
Thomas