gnulib troubles

[Jaroslav Hajek]

hi all,

after a while I tried to build with Intel C++ but the build failed on
liboctave/lo-sysdep.cc.
Eventually I tracked the problem down as follows:

1. #include <fcntl.h> is done from lo-sysdep.cc, which points to libgnu/fcntl.h.
2. libgnu/fcntl.h does #include_next<fcntl.h> which references the
system header.
3. The system fcntl.h #includes <sys/stat.h> which references the
gnulib replacement.

The problem is that at point 3, the code inside system's fcntl.h is
patterned like this:

extern "C" {
...
#include <sys/stat.h>
...
}

This causes the C++ definitions from gnulib

namespace gnulib { ...}

occur inside an extern "C" declaration, which confuses Intel C++
(complains about duplicate decl). I'm not sure whether this is legal,
but it surely a bad idea.
I was able to manually work it around by the following change to libgnu/fcntl.h:

--- a/fcntl.h   2010-03-22 10:25:11.000000000 +0100
+++ b/fcntl.h   2010-03-22 10:25:02.000000000 +0100
@@ -43,7 +43,9 @@
 # include <sys/stat.h>
 #endif
 /* The include_next requires a split double-inclusion guard.  */
+#define __need_system_sys_stat_h
 #include_next <fcntl.h>
+#undef __need_system_sys_stat_h

 #ifndef _GL_FCNTL_H
 #define _GL_FCNTL_H

Is this a defect in gnulib? Or am I missing some settings?
The system headers can be expected to include each other and I don't
think it is a good idea to let them back-reference the gnulib headers,
because this can lead to unpredictable problems. Gnulib should avoid
it.

Maybe someone can comment on this before taking it to the gnulib mailing list?


-- 
RNDr. Jaroslav Hajek, PhD
computing expert & GNU Octave developer
Aeronautical Research and Test Institute (VZLU)
Prague, Czech Republic
url: www.highegg.matfyz.cz