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    On 2000/12/15 Werner Almesberger wrote:
    > LA Walsh wrote:
    >
    > Exception: opaque types; there one would have to go via a __ identifier,
    > i.e.
    >
    > <public>/foo.h defines struct __foo ...;
    > <public>/bar.h includes <public>/foo.h
    > and uses #define FOOSIZE sizeof(struct __foo)
    > <private>/foo.h either typedef struct __foo foo_t;
    > or #define foo __foo /* ugly */
    >

    Easier: public kernel interfaces only work through pointers.
    <public>/foo.h typedef struct foo foo_t;
    foo_t* foo_new();
    <private>/foo.h includes <public>/foo.h
    struct foo { ............... };
    and uses #define FOOSIZE sizeof(foo_t)

    Drawback: public access is slow (always through foo_set_xxxx_field(foo_t*))
    private access from kernel or modules is fast (foo_t->x = ...)
    Advantage: kernel can change, foo_t internals can change and it is binary
    compatible. Even public headers can be kernel version
    independent.

    Too kind-of-classroom-not-real-world-useless-thing ?
    All depends on public access needing full fast paths...

    --
    Juan Antonio Magallon Lacarta #> cd /pub
    mailto:jamagallon@able.es #> more beer

    Linux werewolf 2.2.19-pre1 #1 SMP Fri Dec 15 22:25:20 CET 2000 i686

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