> Can you give me a hint where I can read more about this
> construct '-iquote ./mpi' ?
Only because it's you! ;)
>From man 1 gcc13:
-iquote dir
-isystem dir
-idirafter dir
Add the directory dir to the list of directories to be searched for
header files during preprocessing. If dir begins with = or $SYSROOT,
then the = or $SYSROOT is replaced by the sysroot prefix; see
--sysroot and -isysroot.
Directories specified with -iquote apply only to the quote form of
the directive, "#include "file"". Directories specified with -I,
-isystem, or -idirafter apply to lookup for both the
"#include "file"" and "#include <file>" directives.
You can specify any number or combination of these options on the
command line to search for header files in several directories. The
lookup order is as follows:
1. For the quote form of the include directive, the directory of the
current file is searched first.
2. For the quote form of the include directive, the directories
specified by -iquote options are searched in left-to-right order,
as they appear on the command line.
3. Directories specified with -I options are scanned in left-to-
right order.
4. Directories specified with -isystem options are scanned in left-
to-right order.
5. Standard system directories are scanned.
6. Directories specified with -idirafter options are scanned in
left-to-right order.
You can use -I to override a system header file, substituting your
own version, since these directories are searched before the standard
system header file directories. However, you should not use this
option to add directories that contain vendor-supplied system header
files; use -isystem for that.
The -isystem and -idirafter options also mark the directory as a
system directory, so that it gets the same special treatment that is
applied to the standard system directories.
If a standard system include directory, or a directory specified with
-isystem, is also specified with -I, the -I option is ignored. The
directory is still searched but as a system directory at its normal
position in the system include chain. This is to ensure that GCC's
procedure to fix buggy system headers and the ordering for the
"#include_next" directive are not inadvertently changed. If you
really need to change the search order for system directories, use
the -nostdinc and/or -isystem options.
Laurent
