Re: alignment

[Jun-ichiro itojun Hagino <itojun () iijlab net>]

> >      if not, is it acceptable if we test the feature in
> >      configure.in and use it if available?
> I'd say so (as long as this doesn't involve peppering the code with
> #ifdefs - if the feature *isn't* available, you still have to use the
> EXTRACT macros),

        i was thinking about something like this:

#if GCC
#define __ATTRIBUTE_PACKED__    __attribute__((packed))
#else
#define __ATTRIBUTE_PACKED__
#endif

struct foo {
        u_int32_t bar;
        u_int32_t baz;
} __ATTRIBUTE_PACKED__;

> although note that "__attribute((packed))", at least
> according to the GCC 3.2 manual:
>
>       http://gcc.gnu.org/onlinedocs/gcc-3.2/gcc/Variable-Attributes.html#Variable%20Attributes
>
> changes the layout of the structure, so you'd have to add padding to
> structures that lack it.

        if they don't have padding, they do not work right even now.

itojun
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