Creating makefile c++ that stores .o to a directory

Question

Here is an example of how my datas are stored :

\Program
     main.cpp
     makefile
     \Part1
          file1.cpp
          file1.h
          file2.cpp
          etc
     \Part2
          file3.cpp
          file4.cpp
          file4.h
          etc..
     \Part3
          file5.cpp
          file5.h
          etc..

     \Objects
          file1.o
          file2.o
          file3.o
          file4.o

I think you understood.

My problem is that whatever I try my makefile does not work

clang: error: no input files

or

Undefined symbols for architecture x86_64:

Well, I tried to learn by myself how to build a makefile. I leant the easiest way like :

all:exe
exe: Objects/file1.o Objects/file2.o Objects/file3.o Objects/file4.o Objects/file5.o .....
     $(CPP) $(LFLAGS) Objects/file1.o Objects/file2.o Objects/file3.o ... -o exe

And then, for each .o I ask the makefile to do like :

Objects/file1.0: Part1/file1.cpp
         $(CPP) $(CFLAGS) -o $(OBJ/file1).o Part1/file1.o

But I keep having this issue :

makefile:XX: warning: overriding commands for target .o' makefile:XX: warning: ignoring old commands for target .o'

For every file

I tried to learn how to build makefile more proprelly but it's quite difficult. I tried many, many things and it doesn't work.

Here is what I mean when I say a proper way to write makefile

ALL_CPP=Part1/*.cpp, Part2/*.cpp, Part3/*.cpp, Part4/*.cpp
CPP_FILES := $(wildcard $(ALL_CPP))
OBJ_FILES = $(patsubst $(ALL_CPP),Objects/%.o,$(CPP_FILES))

main: $(OBJ_FILES)
    g++ -o $@ $^

Objects/%.o: Animal/%.cpp
    g++ $(CFLAGS) -c -o $@ $<
Objects/%.o: Enclos/%.cpp
    g++ $(CFLAGS) -c -o $@ $<
Objects/%.o: Menu/%.cpp
    g++ $(CFLAGS) -c -o $@ $<
Objects/%.o: Zoo/%.cpp
    g++ $(CFLAGS) -c -o $@ $<

But of course it doesn't work.

My question is :

How to create a makefile which would work in an environment like mine (with different subfolder) and which would store the .o in a dedicated folder.

I worked using xcode but unfortunately I want a menu where you can navigate using the arrows which doesn't work on the xcode console.

Answer 1

Your second attempt was pretty close.

The problem is with this line

OBJ_FILES = $(patsubst $(ALL_CPP),Objects/%.o,$(CPP_FILES))

The first argument to $(patsubst) is the pattern to match but $(ALL_CPP) isn't a pattern. You want dir/%.c for each directory there. You could make that list of patterns if you really wanted to but there's a better way to do it.

You really have two transformations here. One to replace any leading directory with Objects and one to replace .cpp with .o .

So do them separately.

Use a Substitution Reference for the first part:

OBJ_FILES := $(CPP_FILES:.cpp=.o)

and the notdir and addprefix file name functions for the second part:

OBJ_FILES := $(addprefix Objects/,$(notdir $(OBJ_FILES))

and that should make things work.