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Re: CVS commit: src/sys/dev

On Thu, 26 May 2011, Masao Uebayashi wrote:

> On Thu, May 26, 2011 at 5:39 PM, Iain Hibbert 
> <> wrote:
> > On Thu, 26 May 2011, Masao Uebayashi wrote:
> >> - I can't think of how cfdriver decls can lead to type inconsistency bugs.
> >
> > Ok, somebody makes a mistake and writes
> >
> > extern struct cfdata foo_cd;
> >
> > and it works by chance because the address was zero anyway, then later
> > something else is changed around and all of a sudden, an innocent code
> > causes a kernel panic..
> cfdriver must exist for either embedded/module forms.  If not, it
> should cause link error (if I'm not missing anything).

Of course, it would exist.. that is the bug

file a: /* generated by config(1) */
        struct cfdriver foo_cd;

file b: /* generated by an inattentive programmer */
        extern struct cfdata foo_cd;

> > ok but why change files not affected?  You did not actually remove all
> > inclusions of "ioconf.h" in any case.. (grep ioconf.h *.d finds two more
> > in i386/GENERIC, I didn't look at any other arch)
> Hopefully I'll remove all ioconf.h references in sys/ soon.

I think technically this is a bug in gcc which should be fixed there,
rather than worked around by diluting our sources..  if gcc would simply
generate a label of ".Lnnnnn" for what is a local object, then the symbol
would not appear in the .o file

for instance, pcc does generate such a label and the object code is thus
unchanged. I don't know about clang, or later gcc versions which we may
have access to at some point, the bug may have been fixed already?


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