makefile Advanced Makefile Building from different source folders to different target folders

Example

Main features of this Makefile :

• Automatic detection of C sources in specified folders
• Multiple source folders
• Multiple corresponding target folders for object and dependency files
• Automatic rule generation for each target folder
• Creation of target folders when they don't exist
• Dependency management with gcc : Build only what is necessary
• Works on Unix and DOS systems
• Written for GNU Make

This Makefile can be used to build a project with this kind of structure :

\---Project
    +---Sources
    |   +---Folder0
    |   |       main.c
    |   |       
    |   +---Folder1
    |   |       file1_1.c
    |   |       file1_1.h
    |   |       
    |   \---Folder2
    |           file2_1.c
    |           file2_1.h
    |           file2_2.c
    |           file2_2.h
    \---Build
        |   Makefile
        |   myApp.exe
        |   
        +---Folder0
        |       main.d
        |       main.o
        |       
        +---Folder1
        |       file1_1.d
        |       file1_1.o
        |       
        \---Folder2
                file2_1.d
                file2_1.o
                file2_2.d
                file2_2.o

Makefile

# Set project directory one level above of Makefile directory. $(CURDIR) is a GNU make variable containing the path to the current working directory
PROJDIR := $(realpath $(CURDIR)/..)
SOURCEDIR := $(PROJDIR)/Sources
BUILDDIR := $(PROJDIR)/Build

# Name of the final executable
TARGET = myApp.exe

# Decide whether the commands will be shwon or not
VERBOSE = TRUE

# Create the list of directories
DIRS = Folder0 Folder1 Folder2
SOURCEDIRS = $(foreach dir, $(DIRS), $(addprefix $(SOURCEDIR)/, $(dir)))
TARGETDIRS = $(foreach dir, $(DIRS), $(addprefix $(BUILDDIR)/, $(dir)))

# Generate the GCC includes parameters by adding -I before each source folder
INCLUDES = $(foreach dir, $(SOURCEDIRS), $(addprefix -I, $(dir)))

# Add this list to VPATH, the place make will look for the source files
VPATH = $(SOURCEDIRS)

# Create a list of *.c sources in DIRS
SOURCES = $(foreach dir,$(SOURCEDIRS),$(wildcard $(dir)/*.c))

# Define objects for all sources
OBJS := $(subst $(SOURCEDIR),$(BUILDDIR),$(SOURCES:.c=.o))

# Define dependencies files for all objects
DEPS = $(OBJS:.o=.d)

# Name the compiler
CC = gcc

# OS specific part
ifeq ($(OS),Windows_NT)
    RM = del /F /Q 
    RMDIR = -RMDIR /S /Q
    MKDIR = -mkdir
    ERRIGNORE = 2>NUL || true
    SEP=\\
else
    RM = rm -rf 
    RMDIR = rm -rf 
    MKDIR = mkdir -p
    ERRIGNORE = 2>/dev/null
    SEP=/
endif

# Remove space after separator
PSEP = $(strip $(SEP))

# Hide or not the calls depending of VERBOSE
ifeq ($(VERBOSE),TRUE)
    HIDE =  
else
    HIDE = @
endif

# Define the function that will generate each rule
define generateRules
$(1)/%.o: %.c
    @echo Building $$@
    $(HIDE)$(CC) -c $$(INCLUDES) -o $$(subst /,$$(PSEP),$$@) $$(subst /,$$(PSEP),$$<) -MMD
endef

.PHONY: all clean directories 

all: directories $(TARGET)

$(TARGET): $(OBJS)
    $(HIDE)echo Linking $@
    $(HIDE)$(CC) $(OBJS) -o $(TARGET)

# Include dependencies
-include $(DEPS)

# Generate rules
$(foreach targetdir, $(TARGETDIRS), $(eval $(call generateRules, $(targetdir))))

directories: 
    $(HIDE)$(MKDIR) $(subst /,$(PSEP),$(TARGETDIRS)) $(ERRIGNORE)

# Remove all objects, dependencies and executable files generated during the build
clean:
    $(HIDE)$(RMDIR) $(subst /,$(PSEP),$(TARGETDIRS)) $(ERRIGNORE)
    $(HIDE)$(RM) $(TARGET) $(ERRIGNORE)
    @echo Cleaning done ! 

How to use this Makefile To adapt this Makefile to your project you have to :

1. Change the TARGET variable to match your target name
2. Change the name of the Sources and Build folders in SOURCEDIR and BUILDDIR
3. Change the verbosity level of the Makefile in the Makefile itself or in make call
4. Change the name of the folders in DIRS to match your sources and build folders
5. If required, change the compiler and the flags