dependencies for sources in sub dirs.

dependencies for sources in sub dirs.

[Tobias Grimm]

Hello!

Using gcc 4.0.2, I have the following problem:

Calling "gcc -MM src/foo.c" results in:

foo.o: src/foo.c src/bar.h

But IMHO that's wrong. The manpage says:

       -MT target
           Change the target of the rule emitted by dependency
generation.  By
           default CPP takes the name of the main input file, including any
           path, deletes any file suffix such as .c, and appends the plat-
           form's usual object suffix.  The result is the target.

"By default CPP takes the name of the main input file, including any
path" !!!

So I would assume to get this:

src/foo.o: src/foo.c src/bar.h

But I don't and so the generated dependencies are useless.

Is this a bug in gcc or the manpage, or am I doing something wrong? How
can I force gcc to include the path in the target? -MT is not an option,
because I have several different subdirectories.

Hope someone knows an answer....

Regards,

Tobias

Re: dependencies for sources in sub dirs.

[John Love-Jensen]

Hi Tobias,

Try this experiment:

mkdir src
vi src/Foo.c
(put in something simple:  int foo() { return 3; } )
gcc -c src/Foo.c

Does the Foo.o end up in your current working directory, or in src/Foo.o?

HTH,
--Eljay

Re: dependencies for sources in sub dirs.

[Tobias Grimm]

John Love-Jensen wrote:
> mkdir src
> vi src/Foo.c
> (put in something simple:  int foo() { return 3; } )
> gcc -c src/Foo.c
>
> Does the Foo.o end up in your current working directory, or in src/Foo.o?
>   

In this case, Foo.o is created in ./ instead of src/. But in my 
makefile, I force output with "-o" to src/Foo.o. (See example below).

As a short-hand solution, I modify the dependencies with Sed to prefix 
the target with the full path of the first dependent source:

sed "s/.*: \([^ ]*\/\).*/\1\0/"

This works,  but I thought there might be a way to instruct gcc to 
create the dependencies right in the first place.

Here's the small example:

src/foo.cc:
    #include "bar.h"

    int main()
    {
        return 0;
    }

src/bar.h:
    // EMPTY

Makefile:
    SRCS  = src/foo.c
    OBJS := $(addsuffix .o,$(basename ${SRCS}))

    %.o: %.cc
            gcc $< -o $@

    .dependencies: Makefile
            @gcc -MM -MG $(SRCS) > $@

    -include .dependencies

    test:$(OBJS)
            gcc $(OBJS) -o $@

    clean:
            @-rm -f $(OBJS) .dependencies test

Tobias