[Buildroot] [PATCH v3 2/2] logrotate: use pkg-config for the opt library

Fabio Porcedda fabio.porcedda at gmail.com
Thu Mar 5 08:43:01 UTC 2015


On Thu, Mar 5, 2015 at 9:28 AM, Thomas Petazzoni
<thomas.petazzoni at free-electrons.com> wrote:
> Dear Fabio Porcedda,
>
> On Thu, 5 Mar 2015 00:38:25 +0100, Fabio Porcedda wrote:
>
>> > It's not currently supported in Buildroot, but LOADLIBES is extended by
>> > the logrotate Makefile with -lacl or -lselinux when WITH_ACL or
>> > WITH_SELINUX are used. I'm not sure this will play well with your
>> > proposed solution.
>>
>> Thanks for noticing it.
>> I didn't know that a variable forced from the command line cannot be extended.
>> Now I'm aware of it.
>
> Depends on whether you pass variables in the environment (on the left
> hand side of make) or as make options (on the right hand side of make).
> Demonstration with a simple Makefile:
>
> ===
> FOO = -lbaz
>
> ifeq ($(WITH_SELINUX),yes)
> FOO += -lselinux
> endif
>
> all:
>         @echo $(FOO)
> ===
>
> And now, the different cases:
>
> thomas at skate:/tmp$ make
> -lbaz
> thomas at skate:/tmp$ make FOO=-lpouet
> -lpouet
> thomas at skate:/tmp$ make FOO=-lpouet WITH_SELINUX=yes
> -lpouet
> thomas at skate:/tmp$ make WITH_SELINUX=yes
> -lbaz -lselinux
> thomas at skate:/tmp$ FOO=-lpouet make
> -lbaz
> thomas at skate:/tmp$ FOO=-lpouet make WITH_SELINUX=yes
> -lbaz -lselinux

Even the += behavior is different if the variable is passed on the
left side or on the right side.

===
FOO ?= -lbaz

ifeq ($(WITH_SELINUX),yes)
 FOO += -lselinux
endif

all:
@echo $(FOO)
===

$ make FOO=-lpouet WITH_SELINUX=yes
-lpouet
$ FOO=-lpouet make WITH_SELINUX=yes
-lpouet -lselinux

So if we want that the default option can be changed from the command
line and the makefile will still be able to add options to the same
variable we need to use ?= and pass the variable on the left side.

$ FOO=-lpouet make WITH_SELINUX=yes
-lpouet -lselinux

Best regards
-- 
Fabio Porcedda


More information about the buildroot mailing list