Date: Mon, 25 Sep 2017 21:54:26 -0700 From: Bakul Shah <bakul@bitblocks.com> To: Russell Haley <russ.haley@gmail.com> Cc: freebsd-arm <freebsd-arm@freebsd.org> Subject: Re: Why does this compile? Message-ID: <20170926045441.BB745156E523@mail.bitblocks.com> In-Reply-To: Your message of "Mon, 25 Sep 2017 21:38:33 -0700." <CABx9NuSzSzK87WF07S0B2aZpddKxYJf69kR2gWqBmHxaEQO6JA@mail.gmail.com> References: <CABx9NuSzSzK87WF07S0B2aZpddKxYJf69kR2gWqBmHxaEQO6JA@mail.gmail.com>
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On Mon, 25 Sep 2017 21:38:33 -0700 Russell Haley <russ.haley@gmail.com> wrote:
Russell Haley writes:
>
> int main()
> {
> struct in_pktinfo;
> return 0;
> }
>
> This compiles on FreeBSD current and apparently on 11 too. That's a
> bad thing because it's supposed to fail. I checked in.h and there is
> no struct for in_pktinfo. Not surprisingly, if I remove the include
> altogether, it still compiles.
>
> I assume then that the original author made a mistake? My C is too
> weak and most of my searches don't turn up anything close to what I'm
> looking for.
>
> Any suggestions would be awesome. :)
C allows struct forward references. Mainly so that you can
declare pointers to them (and the actual struct defn may be in
another file). As long as you don't dereference such a ptr in
the first file, the cmompiler won't throw a fit.
If you want to generate an error, create a variable in main():
struct in_pktinfo foo;
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