Can GNU Make streamline building numerous executables with similar rules across a directory structure, allowing compilation from both the main directory and individual project folders?

Building Multiple Executables with Similar Rules Using GNU Make

Question:

Can GNU Make facilitate building multiple executables with similar rules in a directory structure, enabling compilation from both the main directory and individual project directories?

Answer:

Yes, GNU Make can handle this task with a concise and efficient approach. Below are two makefiles that implement the desired functionality:

project.mk:

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

Makefile:

# one directory per project, one executable per directory
project_dirs := $(shell find * -maxdepth 0 -type d )

# executables are named after its directory and go into the same directory
exes := $(foreach dir,${project_dirs},${dir}/${dir})

all : ${exes}

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

Usage:

• Create symbolic links named Makefile to project.mk in each project directory.
• To build a specific project, navigate to the project directory and run make.
• To build all projects, run make from the main directory (all_lessons).
• To clean a specific project, run make clean from the project directory.
• To clean all projects, run make clean from the main directory.

Advantages:

• Easy to implement and suitable for the specified requirements.
• Supports building and cleaning from both the main directory and project directories.
• Automatically generates dependencies and is fully parallelizable.

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