[U-Boot] Understanding uboot child makefiles

[MJ embd]

Thanks, after a long google I figured it out. Will write a post about
it on my blog.

On 9/19/13, Simon Glass <sjg at chromium.org> wrote:
> Hi MJ,
>
> On Mon, Sep 16, 2013 at 8:23 PM, MJ embd <mj.embd at gmail.com> wrote:
>
>> PS: Last message was sent without body, please ignore
>>
>>  0 down vote favorite
>>
>>
>> I am trying to understand a second level makefile of uboot (this
>> makefile was in a sub directory)
>>
>> a) What is the difference between $(COBJS:.o=.c) and  COBJS   :=
>> test_main.o
>>
>
>  $(COBJS:.o=.c) means to evaluate $(COBJS) but replace every .o with .c
>
> COBJS   := test_main.o    means that COBJS is assigned the value
> test_main.o
>
>
>
>> b) What is the meaning of $(call cmd_link_o_target, $(OBJS)). What is
>> the cmd_link_o_target and what is the call statement doing
>>
>
> This is linking the object files together with a partial link (ld -r). See
> config.mk for the definition.
>
>
>> c) Does this line creating 2 targets ?
>>
>> ALL     :=       $(obj).depend $(LIB)
>>
>
> It defines variable ALL to be those two things (the depend file and the
> library). So that
>
> all:    $(ALL)
>
> means that we need to build the depend file and the library.
>
>
>> ===================================Makefile===================
>>
>> include $(TOPDIR)/config.mk
>>
>> LIB     = $(obj)libtest.o
>>
>> SOBJS   := test.o
>>
>> COBJS   := test_main.o
>> COBJS   += diagnostic.o
>>
>>
>> SRCS    := $(SOBJS:.o=.S) $(COBJS:.o=.c)
>> OBJS    := $(addprefix $(obj),$(COBJS) $(SOBJS))
>>
>> ALL     :=       $(obj).depend $(LIB)
>>
>> all:    $(ALL)
>>
>> $(LIB): $(OBJS)
>>         $(call cmd_link_o_target, $(OBJS))
>>
>> #########################################################################
>>
>> # defines $(obj).depend target
>> include $(SRCTREE)/rules.mk
>>
>> sinclude $(obj).depend
>>
>> #########################################################################
>>
>>
> This might help a bit:
>
> http://www.gnu.org/software/make/manual/make.html
>
> Regards,
> Simon
>


-- 
-mj