On Wed, Jul 20, 2005 at 12:54:09PM -0500, Nathan Lynch wrote:
> Matt Domsch wrote:
> > On Tue, Jul 19, 2005 at 06:07:41PM -0600, Moore, Eric Dean wrote:
> > > On Tuesday, July 12, 2005 8:17 PM, Matt Domsch wrote:
> > > > In general, this construct:
> > > >
> > > > > > -#if (LINUX_VERSION_CODE < KERNEL_VERSION(2,6,6))
> > > > > > -static int inline scsi_device_online(struct scsi_device *sdev)
> > > > > > -{
> > > > > > - return sdev->online;
> > > > > > -}
> > > > > > -#endif
> > > >
> > > > is better tested as:
> > > >
> > > > #ifndef scsi_device_inline
> > > > static int inline scsi_device_online(struct scsi_device *sdev)
> > > > {
> > > > return sdev->online;
> > > > }
> > > > #endif
> > > >
> > > > when you can. It cleanly eliminates the version test, and tests for
> > > > exactly what you're looking for - is this function defined.
> > > >
> > >
> > > What you illustrated above is not going to work.
> > > If your doing #ifndef around a function, such as scsi_device_online, it's
> > > not going to compile
> > > when scsi_device_online is already implemented in the kernel tree.
> > > The routine scsi_device_online is a function, not a define. For a define
> > > this would work.
> >
> > Sure it does, function names are defined symbols.
> >
>
> $ cat foo.c
> static int foo(void) { return 0; }
> #ifndef foo
> static int foo(void) { return 0; }
> #endif
>
> $ gcc -c foo.c
> foo.c:3: error: redefinition of 'foo'
> foo.c:1: error: previous definition of 'foo' was here
>
> I believe #ifdef/#ifndef can test only preprocessor symbols.
I was mistaken. Christoph explained to me that it worked on 2.4 due to
the way module symbol versions worked, but isn't that way on 2.6
anymore. My apologies.
--
Matt Domsch
Software Architect
Dell Linux Solutions linux.dell.com & www.dell.com/linux
Linux on Dell mailing lists @ http://lists.us.dell.com
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