Re: [9fans] Don't Plan 9 C compiler initialize the rest of member of a struct?

[Charles Forsyth <charles.forsyth@gmail.com>]

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yes, how true.

On Tue, 2 Apr 2019 at 18:22, Devon H. O'Dell <devon.odell@gmail.com> wrote:

> Also worth noting that any padding bits are zeroed as well for
> aggregate and union types. Not just setting all pointer values to NULL
> and arithmetic types to positive or unsigned zero.
>
> Op di 2 apr. 2019 om 08:17 schreef Skip Tavakkolian
> <skip.tavakkolian@gmail.com>:
> >
> > like this:
> >
> > #include <u.h>
> > #include <stdio.h>
> >
> > struct option {
> > int n;
> > char *s;
> > int flags;
> > };
> >
> >
> > int main(void)
> > {
> > struct option opt = { 1, "test" };
> > static struct option opt2;
> >
> > printf("%d %s %x\n", opt.n, opt.s, opt.flags);
> > printf("%x\n", opt2.flags);
> > return 0;
> > }
> >
> >
> > On Tue, Apr 2, 2019 at 8:02 AM Skip Tavakkolian <
> skip.tavakkolian@gmail.com> wrote:
> >>
> >> I interpret it as: initialize it like a static variable.
> >>
> >> On Tue, Apr 2, 2019 at 7:53 AM Kyohei Kadota <lufia@lufia.org> wrote:
> >>>
> >>> 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
> initializer 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 implicitly 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年4月2日(火) 9:27 Jeremy O'Brien <neutral@fastmail.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 = {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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