Search code examples
c++includec-preprocessorinclude-path

Check if a file is in the include path

In C++ is it possible to check at compile time whether a file with the given name is withing the include path.

I am trying to set up a library which takes compiler settings from a user created file called for example config.h. If the file is not present, the library will default to a workable state.

I would like to do something such as this

#IFINCLUDED config.h
#  include config.h
#else
#    define defaultLibrarySettings
#endif

I guess a workaround would be to just do something like:

#include "config.h
#ifndef defaultLibrarySettings
#   define defaultLibrarySettings
#endif

However the user still needs a "config.h file somewhere in there path, or else they will get an unresolved inclusion.

A final thought would be to do something like

#ifdef USE_EXTERNAL_SETTINGS
#    include "config.h"
#else
#    define defaultLibrarySettings
#endif

This however would require the user to #define USE_EXTERNAL_SETTINGS each time they included my library.

TLDR: is there a simple way to check if a file exists in the include path such as shown in my first example?

Solution

  • you could include and fill in config.h with your default library settings and allow the user to change them. This way the user is also presented with the allowable configurations