Re: [Linux-ia64] Cleanup include/asm-ia64/offsets.h - take 2

[Don Dugger <n0ano@valinux.com>]

Keith-

The number of defines is not the issue.  This issue is that with
the current system these defines are only defined once.  If you
create two different definitions that must match then I can
guarantee that some time in the future the definitions will get
out of sync and we'll spend an inordinate amount of time tracking
down a glitch that never would have occurred if we'd kept with
the current scheme of generating `offsets.h'.

If the only solution you can come up with is to create multiple
definitions then I'm with David, let's just keep the current scheme.

On Tue, May 01, 2001 at 08:31:04AM +1000, Keith Owens wrote:
> On Mon, 30 Apr 2001 08:00:57 -0700, 
> David Mosberger <davidm@hpl.hp.com> wrote:
> >>>>>> On Mon, 30 Apr 2001 14:57:45 +1000, Keith Owens <kaos@ocs.com.au> said:
> >
> >  Keith> Second version of offsets.h cleanup patch.  Instead of
> >  Keith> changing lots of C code, define just the 11 IA64_*_OFFSET
> >  Keith> fields used by C in ptrace.h.
> >
> >This is better, but still no cigar: print_tools knows all the symbols
> >that we might want to use in assembly or C code so I'd rather have it
> >generate all definitions.  I'm OK with using different definitions for
> >C and asm, _provided_ they have the same name and they are
> >automatically generated (to ensure consistency).  Ideally, I'd like
> >these #defines to live in the same place (header file).
> 
> The kernel build system copes reasonably well with shipped files, using
> implicit dependencies which take config changes into account.  kbuild
> has problems with generated files because they require explicit
> dependency information to ensure that they are built before any file
> that uses a generated file is read.
> 
> A single version of offsets.h is a problem because it needs to be
> included in several .c files, each of those .c files requires an
> explicit dependency on the build of offsets.h.  Because offsets.h
> depends on config changes, on header changes and possibly on command
> line parameters to make, it is impractible to work out if any of the
> inputs to offsets.h have changed.  Instead it must be generated every
> time and checked to see if has changed.  That is acceptable for 5
> assembler files, it is not acceptable to regenerate offsets.h for every
> .c file that might include offsets.h.
> 
> There are only 11 IA64_*_OFFSET fields used by .c files.  The cleanest
> solution is to define those 11 fields in the headers that also define
> the structure, which is what I did.  There is no justification for
> complicating the kernel build system any more than it already is, just
> to avoid 11 #defines.
> 
> 
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-- 
Don Dugger
"Censeo Toto nos in Kansa esse decisse." - D. Gale
n0ano@valinux.com
Ph: 303/938-9838