g++ default header include list

Question

While performing a compilation with cross g++ in a Linux machine ( lubuntu 11.10 ) in verbose mode, I can see the list of the default include header directories:

#include <...> search starts here:
/opt/eldk-4.2/usr/bin/../lib/gcc/powerpc-linux/4.2.2/include
/opt/eldk-4.2/ppc_4xx/usr/include/c++/4.2.2/opt/eldk-4.2/ppc_4xx/usr/include/c++/4.2.2/powerpc-linux
/opt/eldk-4.2/ppc_4xx/usr/include/c++/4.2.2/backward
/opt/eldk-4.2/usr/../ppc_4xx/usr/include

Executing the very same g++ binary in another Linux machine (lubuntu 12.10), I get another different list, with less elements:

#include <...> search starts here:
/opt/eldk-4.2/usr/bin/../lib/gcc/powerpc-linux/4.2.2/include

and in which some of the elments seem bad constructed, like the following:

ignoring nonexistent directory "/opt/ppc_4xx/usr/lib/gcc/powerpc-linux/includ../include/c++/4.2.2"

The result is that some code compiling on the first system is not compiling on the second because some headers are not found.

Why is this happening?. Where does this list come from?. Who is responsible for constructing it?. Is it possible to easily change it?.

Any help is appreciated.

Answer 1

You can add directories to the default search path by setting environment variables:

• C_INCLUDE_PATH (for C header files)
• CPLUS_INCLUDE_PATH (for C++ header files).

Alternatively, you can create and edit specfile and place it where G++ looks for them. You can check the path with strace gcc.

Additional documentation on specfiles on GCC page.