Makefiles with source files in different directori

Question

I have a project where the directory structure is like this:

                         $projectroot
                              |
              +---------------+----------------+
              |               |                |
            part1/          part2/           part3/
              |               |                |
       +------+-----+     +---+----+       +---+-----+
       |      |     |     |        |       |         |
     data/   src/  inc/  src/     inc/   src/       inc/

How should I write a makefile that would be in part/src (or wherever really) that could comple/link on the c/c++ source files in part?/src ?

Can I do something like -I$projectroot/part1/src -I$projectroot/part1/inc -I$projectroot/part2/src ...

If that would work, is there an easier way to do it. I've seen projects where there is a makefile in each of the corresponding part? folders. [in this post I used the question mark like in bash syntax]

Answer 1

You can add rules to your root Makefile in order to compile the necessary cpp files in other directories. The Makefile example below should be a good start in getting you to where you want to be.

CC=g++
TARGET=cppTest
OTHERDIR=../../someotherpath/in/project/src

SOURCE = cppTest.cpp
SOURCE = $(OTHERDIR)/file.cpp

## End sources definition
INCLUDE = -I./ $(AN_INCLUDE_DIR)  
INCLUDE = -I.$(OTHERDIR)/../inc
## end more includes

VPATH=$(OTHERDIR)
OBJ=$(join $(addsuffix ../obj/, $(dir $(SOURCE))), $(notdir $(SOURCE:.cpp=.o))) 

## Fix dependency destination to be ../.dep relative to the src dir
DEPENDS=$(join $(addsuffix ../.dep/, $(dir $(SOURCE))), $(notdir $(SOURCE:.cpp=.d)))

## Default rule executed
all: $(TARGET)
        @true

## Clean Rule
clean:
        @-rm -f $(TARGET) $(OBJ) $(DEPENDS)


## Rule for making the actual target
$(TARGET): $(OBJ)
        @echo "============="
        @echo "Linking the target $@"
        @echo "============="
        @$(CC) $(CFLAGS) -o $@ $^ $(LIBS)
        @echo -- Link finished --

## Generic compilation rule
%.o : %.cpp
        @mkdir -p $(dir $@)
        @echo "============="
        @echo "Compiling $<"
        @$(CC) $(CFLAGS) -c $< -o $@


## Rules for object files from cpp files
## Object file for each file is put in obj directory
## one level up from the actual source directory.
../obj/%.o : %.cpp
        @mkdir -p $(dir $@)
        @echo "============="
        @echo "Compiling $<"
        @$(CC) $(CFLAGS) -c $< -o $@

# Rule for "other directory"  You will need one per "other" dir
$(OTHERDIR)/../obj/%.o : %.cpp
        @mkdir -p $(dir $@)
        @echo "============="
        @echo "Compiling $<"
        @$(CC) $(CFLAGS) -c $< -o $@

## Make dependancy rules
../.dep/%.d: %.cpp
        @mkdir -p $(dir $@)
        @echo "============="
        @echo Building dependencies file for $*.o
        @$(SHELL) -ec '$(CC) -M $(CFLAGS) $< | sed "s^$*.o^../obj/$*.o^" > $@'

## Dependency rule for "other" directory
$(OTHERDIR)/../.dep/%.d: %.cpp
        @mkdir -p $(dir $@)
        @echo "============="
        @echo Building dependencies file for $*.o
        @$(SHELL) -ec '$(CC) -M $(CFLAGS) $< | sed "s^$*.o^$(OTHERDIR)/../obj/$*.o^" > $@'

## Include the dependency files
-include $(DEPENDS)

Answer 2

The traditional way is to have a Makefile in each of the subdirectories (part1, part2, etc.) allowing you to build them independently. Further, have a Makefile in the root directory of the project which builds everything. The "root" Makefile would look something like the following:

all:
    +$(MAKE) -C part1
    +$(MAKE) -C part2
    +$(MAKE) -C part3

Since each line in a make target is run in its own shell, there is no need to worry about traversing back up the directory tree or to other directories.

I suggest taking a look at the GNU make manual section 5.7; it is very helpful.

Answer 3

Recursive Use of Make

all:
    +$(MAKE) -C part1
    +$(MAKE) -C part2
    +$(MAKE) -C part3

This allows for make to split into jobs and use multiple cores

Answer 4

I was looking for something like this and after some tries and falls i create my own makefile, I know that's not the "idiomatic way" but it's a begining to understand make and this works for me, maybe you could try in your project.

PROJ_NAME=mono

CPP_FILES=$(shell find . -name "*.cpp")

S_OBJ=$(patsubst %.cpp, %.o, $(CPP_FILES))

CXXFLAGS=-c \
         -g \
        -Wall

all: $(PROJ_NAME)
    @echo Running application
    @echo
    @./$(PROJ_NAME)

$(PROJ_NAME): $(S_OBJ)
    @echo Linking objects...
    @g++ -o $@ $^

%.o: %.cpp %.h
    @echo Compiling and generating object $@ ...
    @g++ $< $(CXXFLAGS) -o $@

main.o: main.cpp
    @echo Compiling and generating object $@ ...
    @g++ $< $(CXXFLAGS)

clean:
    @echo Removing secondary things
    @rm -r -f objects $(S_OBJ) $(PROJ_NAME)
    @echo Done!

I know that's simple and for some people my flags are wrong, but as i said this is my first Makefile to compile my project in multiple dirs and link all of then together to create my bin.

I'm accepting sugestions :D