Re: Cocoa Newbie Question.

On Wed, 11 Jun 2008 15:35:52 -0700 (PDT), piscesboy wrote:

> I tried something different albeit much simpler. This might clear
> things up. Here is the makefile I am using to compile this newer, much
> simpler program of mine that mixes Objective-C and regular C code:

> TARGET=test
> DEBUG=debugtest
> GCC=gcc -ansi -pedantic -Wall -O2 -o
> GCCOP=gcc -ansi -pedantic -Wall -O2 -c
> GCCMOP=gcc -x objective-c -framework Foundation -c
> OBJECTS=main.o Person.o treenode.o
> SOURCE=main.m Person.m treenode.c
> TRASH=*.o *.c~ *.h~ $(TARGET) $(DEBUG) Makefile~

> $(TARGET): $(OBJECTS) $(SOURCE)
> 	$(GCC) $(TARGET) $(OBJECTS)

> main.o: main.m defs.h
> 	$(GCCMOP) main.m

> Person.o: Person.m Person.h
> 	$(GCCMOP) Person.m

> treenode.o: treenode.c treenode.h
> 	$(GCCMOP) treenode.c

> clean:
> 	rm -f $(TRASH)

> My target is called test and depends on the objective-C files main.m,
> and Person.m and the regular C file treenode.c
> This is the error produced when I type 'make':

> gcc -x objective-c -framework Foundation -c main.m
> powerpc-apple-darwin8-gcc-4.0.1: -framework: linker input file unused
> because linking not done
> powerpc-apple-darwin8-gcc-4.0.1: Foundation: linker input file unused
> because linking not done
> gcc -x objective-c -framework Foundation -c Person.m
> powerpc-apple-darwin8-gcc-4.0.1: -framework: linker input file unused
> because linking not done
> powerpc-apple-darwin8-gcc-4.0.1: Foundation: linker input file unused
> because linking not done
> gcc -x objective-c -framework Foundation -c treenode.c
> powerpc-apple-darwin8-gcc-4.0.1: -framework: linker input file unused
> because linking not done
> powerpc-apple-darwin8-gcc-4.0.1: Foundation: linker input file unused
> because linking not done
> gcc -ansi -pedantic -Wall -O2 -o test main.o Person.o treenode.o
> /usr/bin/ld: Undefined symbols:
> .objc_class_name_NSConstantString
> .objc_class_name_NSObject
> .objc_class_name_NSString
> __NSConstantStringClassReference
> _objc_msgSend
> _objc_msgSendSuper
> collect2: ld returned 1 exit status
> make: *** [test] Error 1

You need "-framework Foundation" when you are linking, but not otherwise.
In fact, you did just the opposite, and this accounts for all the warning
messages and the undefined symbols error.

The "-c" flag means "just compiile, don't link".  That's exactly what you
want to do on all the steps except the last one, but you are causing the
compiler to point out repeatedly that it makes no sense to specify both
"-c" and "-framework Foundation" on the same command line.

> I think I know what is going on: that I am not linking the generated
> object files properly. I do not know how to properly invoke the linker
> to link the generated objective-c files mixed with C files.

On the last step, where you are actually doing the linking, you left out
"-framework Foundation".  This is the reason for the "Undefined symbols"
error on the link step.

By the way, "test" is a very poor choice for the name of an executable
program.  Don't be surprised if executing the program appears to produce
no response at all, since "test" is a shell builtin.







-- 
Dave Seaman
Third Circuit ignores precedent in Mumia Abu-Jamal ruling.
<http://www.indybay.org/newsitems/2008/03/29/18489281.php>