Re: partial linking

Ralf Wildenhues wrote:
> Hello,
> 
> * tns1 wrote on Thu, Sep 04, 2008 at 10:12:27PM CEST:
>> I have source tree with many folders containing many .o files each. I  
>> wish to partially link the contents of each folder so I have one  
>> combined .o file (library?) for each folder. These combined (object  
>> files?, libraries?) will go thru a final link step at a later stage in  
>> the build.
> 
> The combined .o files are just objects again, not libraries.
> 
>> Is there anything special about how this partial linking or can I just  
>> do something like:
>>
>> $(OBJS)=a.o b.o c.o
>> mylink.b : $(OBJS)
>> 	ld -o mylink.b $(OBJS)
> 
> BTW, why mylink.b and not mylink.o?  I think some vendor ld's may warn
> about this, or fail to do the right thing.  Also, for partial linking
> you would need to pass -r to ld.

For each sub-folder I ended up with a makefile like:
OBJS=a.o b.o c.o
NEWOBJ=newobjA.lk
FLAGS=-fsigned-char -O0 -mthumb -mthumb-interwork

all: $(OBJS) $(NEWOBJ)

$(OBJS): %o : %c
	arm-elf-gcc $(FLAGS) -I ./../includes -c -o $@ $<

$(NEWOBJ) : $(OBJS)
	arm-elf-ld -r -o ./../$@ $(OBJS)

clean:
	rm *.o

> 
>> Does building in this multi-tiered fashion result in a larger final  
>> image, or can the final link still remove redundancies?
> 
> You did not state what the final link will create.  
The final link is a program image. For this main folder link I am using 
  something like this, although I don't have a clean link yet because my 
script is not complete:

MOREOBJS=newobjA.lk newobjB.lk newobjC.lk

myarm.img : $(MOREOBJS)
	arm-elf-ld -o $@ -T armlink.ld -Map myarm.map $(MOREOBJS) $(OBJS)

clean:
	rm *.img

> FWIW, depending on whether you can assume GNU ld, GNU make, or whether
> you would be willing to use libtool, some optimizations and/or
> simplifications may be applied to your general setup.
> (I can expand but then please specify on which.)
> 

This is a cross platform port, and the two-tier link is legacy from the 
old tools. My main concern is that I have all the basic steps and I am 
not missing something crucial (such as -r and -fsigned-char).