[Python-Dev] To -I(nclude) or not to -I(nclude), that is the question...

[M.-A. Lemburg]

Skip Montanaro wrote:
> In installing mxBase 2.0.4 on my MacOS 10.2.1 system I get warnings like the
> following:
> 
>     gcc -DNDEBUG -g -O3 -Wall -Wstrict-prototypes -Wno-long-double -no-cpp-precomp -Imx/Queue/mxQueue -I/Users/skip/local/include/python2.3 -I/usr/include -I/usr/local/include -c mx/Queue/mxQueue/mxQueue.c -o build/temp.darwin-6.1-Power Macintosh-2.3/mx/Queue/mxQueue/mxQueue/mxQueue.o
>     cc1: warning: changing search order for system directory "/usr/local/include"
>     cc1: warning:   as it has already been specified as a non-system directory
>     cc1: warning: changing search order for system directory "/usr/include"
>     cc1: warning:   as it has already been specified as a non-system directory
> 
> This warning bothers me a bit, as it suggests I'm screwing up the compiler's
> notions about header file search order.  Has anyone else seen this and
> investigated how to get rid of this problem? 

I've had a few bug reports related to this, but all of them
were from Solaris users. The -I/usr/include causes the GCC compiler
to pick up a system stdarg.h header file which causes a compile
error (GCC ships with its own stdarg.h files).

The report for MacOS is new, though. Perhaps this is a generic GCC problem ?
(#include <stdarg.h> should look in the compiler dirs first and only
then scan the additional -I paths)

> This is related to bug
> http://python.org/sf/589427 (which was assigned to me).  It's due to the
> gen_preprocess_options() function in distutils/ccompiler.py.  This warning
> seems to be related to gcc version >= 3.1.
> 
> I have a quick hack in my local copy of distutils/ccompiler.py.  At the
> bottom of gen_preprocess_options() I replaced
> 
>     for dir in include_dirs:
>         pp_opts.append ("-I%s" % dir)
> 
> with 
> 
>     pp_opts.extend (gen_preprocess_includes(include_dirs))
> 
> and added these two functions to the file:
> 
>     def gen_preprocess_includes_macosx_gcc(dirs):
>         """GCC on MacOSX complains if /usr/include or /usr/local/include are
>         mentioned in -I.
>         """
>         pp_opts = []
>         for dir in dirs:
>             if dir not in ("/usr/include", "/usr/local/include"):
>                 pp_opts.append ("-I%s" % dir)
>         return pp_opts
> 
>     def gen_preprocess_includes(dirs):
>         """Generate the -I flags for a compile command."""
>         if sys.platform == "darwin":
>             return gen_preprocess_includes_macosx_gcc(dirs)
> 
>         pp_opts = []
>         for dir in dirs:
>             pp_opts.append ("-I%s" % dir)
>         return pp_opts
> 
> This is an obscure solution, at best.  I'd prefer to at least test the
> compiler and version.  How can I tell what compiler and version will be used
> to compile files, or can't I can this level?  (Seems to me that
> gen_preprocess_options begs to be a method of the CCompiler class.)
> 
> Thx,
> 
> Skip
> 
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-- 
Marc-Andre Lemburg
CEO eGenix.com Software GmbH
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