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    SubjectRe: typedefs and structs [was Re: [PATCH 16/42]: PCI: PCI Error reporting callbacks]
    On Mon, Nov 07, 2005 at 02:41:36PM -0600, linas wrote:
    > On Mon, Nov 07, 2005 at 12:02:57PM -0800, Greg KH was heard to remark:
    > > On Mon, Nov 07, 2005 at 01:36:00PM -0600, linas wrote:
    > > > On Mon, Nov 07, 2005 at 11:02:45AM -0800, Greg KH was heard to remark:
    > > > >
    > > > > No, never typedef a struct. That's just wrong.
    > > >
    > > > Its a defacto convention for most C-language apps, see, for
    > > > example Xlib, gtk and gnome.
    > >
    > > The kernel is not those projects.
    >
    > !!

    Yeah, anyone who thinks that Xlib is the paradigm for coding style...

    > > > Also, "grep typedef include/linux/*" shows that many kernel device
    > > > drivers use this convention.
    > >
    > > They are wrong and should be fixed.
    >
    > What, precisely, is wrong?
    >
    > > See my old OLS paper on all about the problems of using typedefs in
    > > kernel code.
    >
    > Is this on the web somewhere? Google is having trouble finding it.

    http://www.kroah.com/linux/talks/ols_2002_kernel_codingstyle_paper/codingstyle.ps
    and the presentation is at:
    http://www.kroah.com/linux/talks/ols_2002_kernel_codingstyle_talk/html/

    > > > > gcc should warn you
    > > > > just the same if you pass the wrong struct pointer
    > > >
    > > > There were many cases where it did not warn (I don't remember
    > > > the case of subr calls). I beleive this had to do with ANSI-C spec
    > > > issues dating to the 1990's; traditional C is weakly typed.
    > > >
    > > > Its not just gcc; anyoe who coded for a while eventually discovered
    > > > that tyedefs where strongly typed, but "struct blah *" were not.
    > >
    > > Sorry, but you are using a broken compiler if it doesn't complain about
    > > this.
    >
    > Uhh, gcc?

    Try it in the kernel today. You will get a warning if you pass in a
    pointer to a different structure type than it was defined as.

    > I was simply stating a fact about gcc and about standard ANSI-C
    > type-checking that is "well known" to anyone who's been around the
    > block. I was not trying to start an argument.

    Then let's end it here...

    thanks,

    greg k-h
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