Finding out what the GCC include path is [duplicate]

Question

This question already has answers here:

What are the GCC default include directories? (4 answers)

Closed 7 years ago.

I'm trying to programmatically find the #include path on Linux, which as I understand it, in practice means finding what GCC considers it to be. (Is that quite true? How does Clang do it?)

According to http://gcc.gnu.org/onlinedocs/cpp/Search-Path.html some of the components involve the CPU architecture and the GCC version; the latter in particular seems tricky; I suppose it could be obtained by running gcc --version and parsing the output (or gcc -v), but this seems inelegant at best and fragile at worst. Doing it from within one's code assuming one's program is being compiled with GCC might be another option, but it would require depending on that assumption.

What's the recommended way to do it?

Answer 1

The command

echo | gcc -E -Wp,-v -

will show the include path in use.

Answer 2

I'm not sure what you mean by the recommended way to find the include path. The standard way is as given below (for c and c++):

$ `gcc -print-prog-name=cc1` -v
ignoring nonexistent directory "/usr/lib/gcc/x86_64-linux-gnu/4.7/../../../../x86_64-linux-gnu/include"
#include "..." search starts here:
#include <...> search starts here:
 /usr/lib/gcc/x86_64-linux-gnu/4.7/include
 /usr/local/include
 /usr/lib/gcc/x86_64-linux-gnu/4.7/include-fixed
 /usr/include
End of search list.
^C
$ `gcc -print-prog-name=cc1plus` -v
ignoring nonexistent directory "/usr/lib/gcc/x86_64-linux-gnu/4.7/../../../../x86_64-linux-gnu/include"
#include "..." search starts here:
#include <...> search starts here:
 /usr/include/c++/4.7
 /usr/include/c++/4.7/x86_64-linux-gnu
 /usr/include/c++/4.7/backward
 /usr/lib/gcc/x86_64-linux-gnu/4.7/include
 /usr/local/include
 /usr/lib/gcc/x86_64-linux-gnu/4.7/include-fixed
 /usr/include
End of search list.
^C