C++ Makefile headers and cpp

Question

I am trying to create a Makefile but am really struggling. I have 3 files; main.cpp, garage.cpp, and garage.hpp. The following command works but I cannot figure out how to turn it into a makefile. Any help would be greatly appreciated. The -std=c++0x is important because if I remove that and replace it with something else it won't compile. Thanks again.

Working

g++ -std=c++0x -Wall -o main main.cpp garage.hpp garage.cpp

Answer 1

FYI, it's not right to add header files (garage.hpp) to the compile/link line. Only source files (.cpp) should be put on the compile line.

@gowrath's solution is easy to understand but it's exactly the same as your command line solution: it doesn't take advantage of any of make's capabilities. It would be easier to just write a shell script or alias to do this than use a makefile.

@Rahul's solution spells everything out, but doesn't take advantage of any features of make that allow you to reduce typing or effort when writing a makefile.

Make actually has a large number of built-in rules. In order to customize them you simply set the values of standard variables and make will do the rest. You could write this makefile:

CXX = g++
CXXFLAGS = -std=c++0x -Wall

OBJECTS = main.o garage.o

main: $(OBJECTS)
        $(CXX) $(CXXFLAGS) -o $@ $^

$(OBJECTS): garage.hpp

The link rule uses automatic variables to avoid having to retype the target (main) or prerequisites (main.o, garage.o).

The last line ensures that if the garage.hpp file changes, make knows it has to recompile the source files. You don't have to write rules to tell make how to compile the source files: it already knows how to do it.

Answer 2

Makefile is very effective way of compiling our code. Makefile uses time stamp to detect any changes in file and compile only those file that are changed. This saves lot of time.

Below makefile will do your job perfectly.

 output: main.o garage.o
        g++ -std=c++0x -Wall main.o garage.o -o output

 main.o: main.cpp
        g++ -c main.cpp

 garage.o: garage.cpp garage.hpp
        g++ -c garage.cpp

 clean:
        rm *.o output

Spaces before g++ and rm command is a tab

Name this file as Makefile to compile type make. This will create a executable named output

And to run the executable using ./output