Make and c++ files, "includes" in the cpp - c++

Question

This is my current makefile:
# Compiler #
CXX = g++
DEBUG = -g
LFLAGS =
CXXFLAGS = -Wall
# Directories #
SRCDIR = src/
INCDIR = include/
BUILDDIR = build/
BINDIR = bin/
# Objects #
OBJ_NAMES = main.o dfa.o dfaException.o state.o
OBJS = $(addprefix $(BUILDDIR), $(OBJ_NAMES))
# Output #
NAME = pract3
TARGET = $(BINDIR)pract3
# Clean #
ifeq ($(OS),Windows_NT)
RM = del /q /s $(BUILDDIR:/=\)*.o $(BINDIR:/=\)$(NAME)*
else
RM = rm -rf $(BUILDDIR)*.o $(TARGET)*
endif
# Files #
$(TARGET): $(OBJS)
$(CXX) $(CXXFLAGS) $(LFLAGS) $(OBJS) -o $(TARGET)
$(BUILDDIR)%.o: $(SRCDIR)%.cpp
$(CXX) $(CXXFLAGS) $(LFLAGS) -c $< -o $#
clean:
$(RM)
And this is my project tree:
Porject/
bin/
build/
doc/
...
include/
connection.hpp
dfa.hpp
dfaException.hpp
state.hpp
src/
dfa.cpp
dfaException.cpp
main.cpp
state.cpp
Makefile
Readme
Now, I'm having three "problems".
First I want my makefile to create the bin and build directories just in case they aren't. I guess I just have to use:
mkdir $(BUILDDIR)
mkdir $(BINDIR)
But where should I put them ? And also, how can I prevent mkdir and rm (or del in windows) messages like "Cant find ..." or "x directory already exists ... "
Second, I'm guessing I can read the objects name from src/ (converting the .cpp to .o), but how can I read the file names from a directory ?
Last, I have one template class: connection.hpp (all functions are in the header). This file is included in state.hpp using: #include "../include/connection.hpp". I ran make one time with all correct and then I purposely make a syntax error in connection.hpp. Then I ran make again, but It only compiled the target file using the .o files in build without any error. Everytime I want to edit connection.hpp I have to use make clean and then make. Is there any better way to do this ?

Answer 1

If you need a directory to exist before you can proceed, simply put
mkdir -p ${DIRECTORY}
before you need it in your rule. If the directory already exists, mkdir -p will happily do nothing.
Likewise, if you use rm -f FILE, it should not complain if FILE does not exist in the first place.
There is no portable way to create a variable that holds the names of all files in a directory. But you are already using GNU Make features anyway, so you can just use
SOURCES = $(wildcard ${SRCDIR}/*.cpp)
and then
OBJECTS = $(SOURCES:.cpp=.o)
to transform them into object file names. You'll probably want to replace the leading directory name as well, I guess.
You didn't list any *.hpp files as prerequisites in your make file. You can either manually add them like
foo.o: foo.cpp bar.hpp baz.hpp
but that becomes unpleasant very quickly. Another trick is to use the compiler to tell you the headers (transitively) #included by a file. If you are using GCC, you can run
gcc -MM foo.cpp
to have it output above make-file snippet. You can put a pattern rule like the following
%.deps: %.cpp
${CXX} -MM ${CPPFLAGS} $< > $#
into your make-file and then include the generated *.deps files.
include $(SOURCES:.cpp=.deps)
GNU Make will be smart enough to first parse the make-file, recognize that the *.deps files don't exist and therefore cannot be included but figure out that there is a rule to generate them. So it will execute that rule and then continue parsing the make-file.
I have learned that trick from Peter Miller's great article Recursive Make Considered Harmful which is a good read if you want to learn how to write good make-files.