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    SubjectRe: typedefs and structs [was Re: [PATCH 16/42]: PCI: PCI Error reporting callbacks]
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    On Mon, Nov 07, 2005 at 11:02:45AM -0800, Greg KH was heard to remark:
    >
    > > I'm not to clear on what "sparse" can do; however, in the good old days,
    > > gcc allowed you to commit great sins when passing "struct blah *" to
    > > subroutines, whereas it stoped you cold if you tried the same trick
    > > with a typedef'ed "blah_t *". This got me into the habit of turning
    > > all structs into typedefs in my personal projects. Can we expect
    > > something similar for the kernel, and in particular, should we start
    > > typedefing structs now?
    >
    > 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. Also, "grep typedef include/linux/*"
    shows that many kernel device drivers use this convention.

    > 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.

    > (and all of your code
    > builds without warnings, right?)

    :-/ Yes, of course.

    --linas
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