sagecc applied to g++ pre-processed files.

Once of my source files included a system header file that had the
#include_next directive. Evidently this directive is recognized by the
g++ compiler but not be sagecc.

In order to execute sagecc on such a file I pre-processed this file. The
pre-processed file had the following line that I assumed to be a comment.

# 1 "/usr/local/lib/gnu/lib/g++-include/_G_config.h" 1 3

When I executed sagecc on the pre-processed file, there was a parse error
in the file _G_config.h. The error vanished when I commented the above

I am assumming that sagecc included the above while. Why is it including
the above file? How can I avoid the error without removing all such
comment lines in the pre-processed file?

Thank you very much.