Listing all header files your cpp depends on

I needed to extract certain Boost headers from its huge code base for memory mapped file & shared memory containers. The first idea came to my mind was a simple grep command for ‘#include’ statements and then parse the paths. This is simple but not so useful for the cases when headers are conditionally included. For example:

#ifndef NO_STL
#include "my_class_no_stl.h"
#include "my_class_stl.h"

To be honest, grep won’t be able to handle it. We need a full fledged C++ pre-processor to correctly include headers and pass necessary values/definitions (it’s done with -D for g++). I was struggling a bit and got a tip from Ralph. It turned out to be very simple:

g++ -D NO_STL -I A_PATH -M source.cpp # to get all headers, including system headers
g++ -D NO_STL -I A_PATH -MM source.cpp # to get all headers, except system headers
g++ -D NO_STL -I A_PATH -H source.cpp # to print all headers nested in as a tree


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