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From: Kyohei Kadota <lufia@lufia.org>
Date: Tue,  2 Apr 2019 23:52:19 +0900
Message-ID: <CAFMepcnz+swU3hDSEb0AacN2X8VTZA9i51j7HCc+0HxGSFCr0A@mail.gmail.com>
To: Fans of the OS Plan 9 from Bell Labs <9fans@9fans.net>
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Subject: Re: [9fans] Don't Plan 9 C compiler initialize the rest of member
 of a struct?
Topicbox-Message-UUID: f8331b5e-ead9-11e9-9d60-3106f5b1d025

Thank you for a reply.

I read spec on http://www.open-std.org/jtc1/sc22/WG14/www/docs/n1256.pdf
then I'm confusing.
This spec describes Initialization:

> 6.7.8 Initialization, p127
>
> 19 The initialization shall occur in initializer list order, each initial=
izer provided for a
> particular subobject overriding any previously listed initializer for the=
 same subobject;132)
> all subobjects that are not initialized explicitly shall be initialized i=
mplicitly the same as
> objects that have static storage duration.

What is "be initialized implicitly the same as objects that have
static storage duration" mean?

2019=E5=B9=B44=E6=9C=882=E6=97=A5(=E7=81=AB) 9:27 Jeremy O'Brien <neutral@f=
astmail.com>:
>
> 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 =3D {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 no=
t initialized explicitly, its value is indeterminate."
>
> Stack variable =3D=3D automatic storage duration. This appears to be corr=
ect behavior to me.
>