From: Charles Forsyth <charles.forsyth@gmail.com>
To: Fans of the OS Plan 9 from Bell Labs <9fans@9fans.net>
Subject: Re: [9fans] Don't Plan 9 C compiler initialize the rest of member of a struct?
Date: Tue, 2 Apr 2019 01:35:17 +0100 [thread overview]
Message-ID: <CAOw7k5hwbS28NsfRj9b6H8j=ydbNQ2xrL0KNmr_KkzmVSZ5vQQ@mail.gmail.com> (raw)
In-Reply-To: <43a5572d-ea50-41a8-9897-9900f13c5a00@www.fastmail.com>
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Yes, that's normal C behaviour. Only external and static storage is
guaranteed to be zero. In a modern environment it seems a little mean,
especially since you gave opt a partial initial value, but there are no
half-measures in C.
On Tue, 2 Apr 2019 at 01:27, Jeremy O'Brien <neutral@fastmail.com> wrote:
> On Mon, Apr 1, 2019, at 11:33, Kyohei Kadota wrote:
> > Hi, 9fans. I use 9legacy.
> >
> > About below program, I expected that flags field will initialize to
> > zero but the value of flags was a garbage, ex, "f8f7".
> > Is this expected?
> >
> > ```
> > #include <stdio.h>
> >
> > struct option {
> > int n;
> > char *s;
> > int flags;
> > };
> >
> > int
> > main(void)
> > {
> > struct option opt = {1, "test"};
> > printf("%d %s %x\n", opt.n, opt.s, opt.flags);
> > return 0;
> > }
> > ```
> >
> >
>
> According to C99: "If an object that has automatic storage duration is not
> initialized explicitly, its value is indeterminate."
>
> Stack variable == automatic storage duration. This appears to be correct
> behavior to me.
>
>
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next prev parent reply other threads:[~2019-04-02 0:35 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-01 15:32 Kyohei Kadota
2019-04-01 23:49 ` Skip Tavakkolian
2019-04-02 14:44 ` Kyohei Kadota
2019-04-02 0:26 ` Jeremy O'Brien
2019-04-02 0:35 ` Charles Forsyth [this message]
2019-04-02 0:35 ` [9fans] Don't Plan 9 C compiler initialize the rest of member of a?struct? Kurt H Maier
2019-04-02 1:20 ` Dan Cross
2019-04-02 2:22 ` Kurt H Maier
2019-04-02 3:06 ` Skip Tavakkolian
2019-04-02 8:02 ` David du Colombier
2019-04-02 10:38 ` Charles Forsyth
2019-04-02 16:25 ` Anthony Martin
2019-04-02 16:37 ` Charles Forsyth
2019-04-02 14:52 ` [9fans] Don't Plan 9 C compiler initialize the rest of member of a struct? Kyohei Kadota
2019-04-02 15:02 ` Skip Tavakkolian
2019-04-02 15:14 ` Skip Tavakkolian
2019-04-02 16:18 ` Devon H. O'Dell
2019-04-02 19:57 ` Charles Forsyth
2019-04-02 15:04 ` Charles Forsyth
2019-04-02 15:16 ` Kyohei Kadota
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