How to Build Multiple Executables with Similar Rules Using GNU Make?

Building Multiple Executables with Similar Rules Using GNU Make

While Scons is a capable build tool, implementing the desired functionality can be challenging. A more straightforward approach is to utilize GNU Make, which allows for easy building and cleaning from both top-level and individual project directories.

Makefile Setup

The provided makefiles enable building and cleaning from both the all_lessons directory and individual project directories. Each project's executable is named after its directory.

Project Structure

To achieve this, you will need to set up a project structure similar to the example provided:

all_lessons/
    helloworld/
        lesson.cpp
        main.cpp
    even_or_odd/
        lesson.cpp
        main.cpp
    calculator/
        lesson.cpp
        user_created_add.cpp
        main.cpp

Makefile Contents

project.mk

all :
% : forward_ # build any target by forwarding to the main makefile
    $(MAKE) -C .. project_dirs=$(notdir ${CURDIR}) $@
.PHONY : forward_

Makefile

# project configuration

project_dirs := $(shell find * -maxdepth 0 -type d )
exes := $(foreach dir,${project_dirs},${dir}/${dir})

all : ${exes}

# rules

.SECONDEXPANSION:
objects = $(patsubst %.cpp,%.o,$(wildcard $(dir )*.cpp))

# link
${exes} : % : $$(call objects,$$*) Makefile
    g++ -o $@ $(filter-out Makefile,$^) ${LDFLAGS} ${LDLIBS}

# compile .o and generate dependencies
%.o : %.cpp Makefile
    g++ -c -o $@ -Wall -Wextra ${CPPFLAGS} ${CXXFLAGS} -MD -MP -MF ${@:.o=.d} $<

.PHONY: clean
clean :
    rm -f $(foreach exe,${exes},$(call objects,${exe})) $(foreach dir,${project_dirs},$(wildcard ${dir}/*.d)) ${exes}

# include dependency files
-include $(foreach dir,${project_dirs},$(wildcard ${dir}/*.d))

Usage

Building from Individual Project Directories

[project_directory]$ ln -s ../project.mk Makefile  # create a symlink
[project_directory]$ make

Building from the Top-Level Directory

[all_lessons]$ make

Cleaning Individual Project Directories

[project_directory]$ cd ..
[all_lessons]$ make clean

Cleaning All Projects

[all_lessons]$ make clean

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