Question

Hello (I am using Windows, mingw g++ compiler and mingw32-make)
To generalize my question I would like to learn how to write a c++ source file as follows:

Assuming that foo.cpp depends on foo.h where foo.cpp is in src\ and foo.h is in include\
// foo.cpp
#include "foo.h"

Normally I would just write it like this
//foo.cpp
#include "..\include\foo.h"

but I have found that as my project grows, and I begin to need more organization, that this method isn’t dynamic enough. Reason being I have to change every include for every file if I want to move foo.h to a new directory (say include\bar\foo.h). Is there a way for make to achieve this. If so can it be done for header file dependencies as well.

As a side note I am new to makefiles. I am not even sure that it knows these includes are there since they are within the code (in fact from what I understand it doesn’t). That would lead me to an unfortunate secondary question, which is can make see these includes? If not is it possible to change it so that it can? Feel free to answer how you would approach this problem because I have a feeling I am going about this the wrong way by putting the includes in the file rather than linking them in the makefile.

Answer 1

The compiler is always looking into some default paths to look for .h-files. You can add your path.

For example gcc takes multiple -I arguments which contain a path. In your foo.cpp you do:

#include "foo.h"

and when compiling you say:

g++ -I../include foo.cpp -c [other options]

.

Regarding the second part of your question: The makefile and the call to make does not normally know anything about the files to be compiled and about your project. However there are several default variables and directives in make which lead to that impression: It could be, that in your environment you only need to change the CFLAGS or CPPFLAGS variable to add the -I-argument and it will work.