Question

The directory structure of my C++ project is

/..
   makefile     <- the makefile is in root
   /include     <- subdirectory that has to be included while compiling
   /obj         <- target place for all *.o and final executable
   /src         <- sources

And my current makefile is:

CC=g++
CFLAGS=-c -Wall -std=c++11

INC=-Iinclude
SRC=src
TGT=obj

all: myapp

myapp: myapp.o
    $(CC) $(TGT)/myapp.o -o $(TGT)/myapp

myapp.o:
    $(CC) $(CFLAGS) $(INC) $(SRC)/myapp.cpp -o $(TGT)/myapp.o

clean:
    rm -rf $(TGT)
    mkdir $(TGT)

This worked for my first file. I am a total makefile novice – please help me compile all files under the /src directory and link them to an executable in /obj directory.

the makefile has to work under Windows, I am using MinGW and MSYS

Answer 1

Add a list of your source files:

SOURCES = $(wildcard $(SRC)/*.cpp)

and a list of corresponding object files:

OBJS = $(addprefix $(TGT)/, $(notdir $(SOURCES:.cpp=.o)))

and the target executable:

$(TGT)/myapp: $(OBJS)
    $(CXX) $(LDFLAGS) $(OBJS) -o $@

The rule for building the objects:

$(TGT)/%.o: $(SRC)/%.cpp
    $(CXX) $(CXXFLAGS) -c $< -o $@

Now you must specify are the options for g++:

INCLUDES = -Iinclude
CXXFLAGS = -Wall -std=c++11 $(INCLUDES)

And everything together:

SRC=src
TGT=obj
INCLUDES = -Iinclude
CXXFLAGS = -Wall -std=c++11 $(INCLUDES)
SOURCES = $(wildcard $(SRC)/*.cpp)
OBJS = $(addprefix $(TGT)/, $(notdir $(SOURCES:.cpp=.o)))

$(TGT)/%.o: $(SRC)/%.cpp
    $(CXX) $(CXXFLAGS) -c $< -o $@

$(TGT)/myapp: $(OBJS)
    $(CXX) $(LDFLAGS) $(OBJS) -o $@

It is important, that in front of $(CXX) ... there must be a “tab” character, not spaces.