Recursive Makefile howto

Recursive Makefile howto

[Manavendra Nath Manav]

Hi All,

I have developed a Makefile which recursively builds the code spread
across multiple directories, each having it's own Makefile.

build_all: targetA \
               targetB \
               target C

Now, the problem is that even when the Makefile of targetA fails, the
master Makefile continues building with targetB and targetC. I can
also see the make errors being printed on console. I want the make to
stop immediately at the first error encountered in any target
Makefile. How to do this?

-- 
Manavendra Nath Manav

Recursive Makefile howto

[Kristof Provost]

On 2012-01-27 11:43:10 (+0530), Manavendra Nath Manav <mnm.kernel@gmail.com> wrote:
> I have developed a Makefile which recursively builds the code spread
> across multiple directories, each having it's own Makefile.
> 
> build_all: targetA \
>                targetB \
>                target C
> 
> Now, the problem is that even when the Makefile of targetA fails, the
> master Makefile continues building with targetB and targetC. I can
> also see the make errors being printed on console. I want the make to
> stop immediately at the first error encountered in any target
> Makefile. How to do this?
> 
It would be a lot easier to help you if you'd post the relevant bits of
your Makefile.

Dusting off my crystal ball, I see in the mists that your makefile looks
something like this:

build:
        for d in $(DIRS) ; \
        do \
                $(MAKE) -C $$d $@ ; \
        done

The problem here is that make considers the whole for loop as one and
doesn't get the exit status of each sub-make, but only of the last one.

Try something like this instead:

build:
        for d in $(DIRS) ; \
        do \
                $(MAKE) -C $$d $@ || exit $? ; \
        done

Regards,
Kristof

Recursive Makefile howto

[Manavendra Nath Manav]

On Fri, Jan 27, 2012 at 2:32 PM, Kristof Provost <kristof@sigsegv.be> wrote:
> On 2012-01-27 11:43:10 (+0530), Manavendra Nath Manav <mnm.kernel@gmail.com> wrote:
>> I have developed a Makefile which recursively builds the code spread
>> across multiple directories, each having it's own Makefile.
>>
>> build_all: targetA \
>> ? ? ? ? ? ? ? ?targetB \
>> ? ? ? ? ? ? ? ?target C
>>
>> Now, the problem is that even when the Makefile of targetA fails, the
>> master Makefile continues building with targetB and targetC. I can
>> also see the make errors being printed on console. I want the make to
>> stop immediately at the first error encountered in any target
>> Makefile. How to do this?
>>
> It would be a lot easier to help you if you'd post the relevant bits of
> your Makefile.
>
> Dusting off my crystal ball, I see in the mists that your makefile looks
> something like this:
>
> build:
> ? ? ? ?for d in $(DIRS) ; \
> ? ? ? ?do \
> ? ? ? ? ? ? ? ?$(MAKE) -C $$d $@ ; \
> ? ? ? ?done
>
> The problem here is that make considers the whole for loop as one and
> doesn't get the exit status of each sub-make, but only of the last one.
>
> Try something like this instead:
>
> build:
> ? ? ? ?for d in $(DIRS) ; \
> ? ? ? ?do \
> ? ? ? ? ? ? ? ?$(MAKE) -C $$d $@ || exit $? ; \
> ? ? ? ?done
>
> Regards,
> Kristof
>

Hi Kristof,

Your crystal ball insight was fairly accurate. The syntax "$(MAKE) -C
$$d $@ || exit $? ;" is both new and helpful to me. For more clarity,
the format of my Makefile is like this:

my_exec: Build_sqllib	\
	Create_obj_dir		\
	objs/server/foo.o	\
	objs/server/bar.c	
	$(LINK) -o my_exec	\
	objs/server/foo.o	\
	objs/server/bar.c

Build_sqllib:
	cd src/sqllib;				\
	rm -rf LIBS/*;				\
	make;					\
	rm -f $(CURDIR)/sqllib.a;		\
	cp -fv LIBS/sqllib.a $(CURDIR)/lib/sqllib.a;\
	cd $(CURDIR);

Create_obj_dir:
	mkdir -p objs/server		\
		objs/html			\
		objs/log			\
		objs/cipher		\
		objs/curse		\
		objs/crypto		\
		objs/protocol

objs/server/foo.o:			\
	src/server/foo.c
	$(LINK) -c			\
		-o objs/server/foo.o	\
		src/server/foo.c

Now, I am getting error in the make part of "Build_sqllib" but the
makefile continues to next line. I guess, I need to add "|| exit" also
with this make command. Kristof, can you pls also explain me the
meanings of $$d, $@, and $? as used in Makefiles.
-- 
Manavendra Nath Manav

Recursive Makefile howto

[Kristof Provost]

On 2012-01-27 17:38:11 (+0530), Manavendra Nath Manav <mnm.kernel@gmail.com> wrote:
> Now, I am getting error in the make part of "Build_sqllib" but the
> makefile continues to next line. I guess, I need to add "|| exit" also
> with this make command. Kristof, can you pls also explain me the
> meanings of $$d, $@, and $? as used in Makefiles.

$$d is not a make variable, but a shell variable. The double '$' is an
escape sequence. In fact, $? should be $$?, because we want the shell
to interpret it. I suspect it gets replaced by an empty string, and in
that case exit returns the exit status from the previous command.
We can just remove $$? in other words.

$@ is a make variable, an automatic variable. It always contains the
file name of the target. 

Regards,
Kristof

Recursive Makefile howto

[Bernd Petrovitsch]

On Fre, 2012-01-27 at 10:02 +0100, Kristof Provost wrote:
[...]
> Try something like this instead:
> 
> build:
>         for d in $(DIRS) ; \
>         do \
>                 $(MAKE) -C $$d $@ || exit $? ; \
>         done

Or 

build:
        set -e; for d in $(DIRS); \
        do \
                $(MAKE) -C $$d $@; \
        done

Read bash' manual page for what "set -e" does.

	Bernd
-- 
Bernd Petrovitsch                  Email : bernd at petrovitsch.priv.at
                     LUGA : http://www.luga.at

Recursive Makefile howto

[Dave Hylands]

Hi Manavendra,

On Thu, Jan 26, 2012 at 10:13 PM, Manavendra Nath Manav
<mnm.kernel@gmail.com> wrote:
> Hi All,
>
> I have developed a Makefile which recursively builds the code spread
> across multiple directories, each having it's own Makefile.

You may want to reconsider your approach:
http://aegis.sourceforge.net/auug97.pdf
http://evbergen.home.xs4all.nl/nonrecursive-make.html

-- 
Dave Hylands
Shuswap, BC, Canada
http://www.davehylands.com

Recursive Makefile howto

[Manavendra Nath Manav]

On Fri, Jan 27, 2012 at 9:28 PM, Dave Hylands <dhylands@gmail.com> wrote:
> Hi Manavendra,
>
> On Thu, Jan 26, 2012 at 10:13 PM, Manavendra Nath Manav
> <mnm.kernel@gmail.com> wrote:
>> Hi All,
>>
>> I have developed a Makefile which recursively builds the code spread
>> across multiple directories, each having it's own Makefile.
>
> You may want to reconsider your approach:
> http://aegis.sourceforge.net/auug97.pdf
> http://evbergen.home.xs4all.nl/nonrecursive-make.html
>
> --
> Dave Hylands
> Shuswap, BC, Canada
> http://www.davehylands.com

Thanks Dave, I went through both the links provided by you and the
make process is pretty much clear to me now. The following two points
I would want elaborate from the paper:
1. As a rule of thumb: always use immediate evaluation assignment
unless you knowingly want deferred evaluation.
2. You will get more accurate builds of your project if you use
whole-project make rather than recursive make.

-- 
Manavendra Nath Manav