Override default header search path

Question

I'm currently trying to get a program to compile on a system that I don't have control over.

The problem that I'm having is the include directories look like this:

/usr/include:
gmpxx.h gmp.h

/usr/local/include:
gmp.h

In my cpp file, I use

#include <gmpxx.h>

and this finds the correct file in /usr/include, however when gmpxx.h includes gmp.h, it pulls it from /usr/local/include, which breaks the build.

Right now, I see 3 very ugly solutions to the problem

1. In my cpp file, add #include </usr/include/gmp.h>
   Having an absolute include path is pretty ugly and non-portable, and I think that this sort of thing should belong in the Makefile instead of the source.

2. add the -nostdinc flag to my makefile, and specify the include paths by hand

3. create local symlinks to the libraries that I really want, and then do local includes (#include "gmp.h")

Is there a better solution that I'm missing?

Answer 1

The search paths for includes are taken in the following order:

• The -I command-line option.
• The CPLUS_INCLUDE_PATH environment variable.
• The standard defaults.

So, you can use either of the first two (whichever seems better/more convenient for your purposes).