Re: [PATCH] Add -nostdinc to TARGET_CFLAGS

[Felix Zielcke]

Am Sonntag, den 15.11.2009, 12:35 +0100 schrieb Robert Millan:
> On Sun, Nov 15, 2009 at 12:17:50PM +0100, Felix Zielcke wrote:
> > 
> > The advantage is that this does exatly what we want for the target.
> > Remove /usr/include from the include search directories but still keep
> > the gcc internal one for e.g. stdarg.h
> > As far as I understand the gcc manual, isystem adds this directory to
> > the search path and treats all headers there in as system headers.
> > And with the = between -isystem and $(srcdir) it actually uses
> > ${sysroot}{$srcdir} but we don't use any --sysroot or -isysroot.
> > The arguments we currently have there just look wrong with my understand
> > of the gcc manual
> 
> Ah, I see..
> 
> > $ cat test.c
> > #include <stdarg.h>
> > #include <stdint.h>
> > 
> > int main (void)
> > {
> >   return 0;
> > }
> > 
> > $ srcdir=$PWD builddir=$PWD gcc -isystem=$srcdir/include -I$srcdir/include 
> > -I$builddir -I$builddir/include test.c -o test && ls test
> > test
> > $ srcdir=$PWD builddir=$PWD gcc -nostdinc -isystem $(gcc 
> > -print-file-name=include) -I$srcdir/include -I$builddir -I$builddir/include 
> > test.c 
> > test.c:2:20: error: stdint.h: No such file or directory
> 
> We used -isystem as a way of excluding system headers but not gcc headers.
> With the -print-file-name trick this seems to be no longer necessary, right?
> 
> So why not "-nostdinc -I$(gcc -print-file-name=include)" instead?

I think we should use -isystem for the gcc internal header files not -I,
but I just tested experimental branch with -I instead of -isystem and
also compiles cleanly (except the usual grub.texi warnings)

As said on IRC already:
http://gcc.gnu.org/onlinedocs/cpp/System-Headers.html


-- 
Felix Zielcke
Proud Debian Maintainer and GNU GRUB developer