Re: C99 Initialisers

[Jakub Jelinek <jakub@redhat.com>]

On Tue, Aug 12, 2003 at 12:03:21PM +0200, Geert Uytterhoeven wrote:
> > > I sure would.  Oh, you can drop the .class, .class_mask, and
> > > .driver_data lines, and then it even looks cleaner.
> > Just a quick question. if we drop these, will they _always_
> > be initialised 0 ? I have made a test to see, and it seemed as though,
> > but I would like to be 100% sure.
> 
> For globals and static locals: yes.
> For non-static locals: no.

No, for all initializers members which are not explicitely initialized are
zero initialized.
Only if you provide no initializer at all, globals/static locals will
still be zero initializers while non-static locals may contain anything.
So, if you write:

struct A { int a; int b; int c; int d; };
void bar (void *);
void foo (void)
{
  struct A a = { .a = 21 };
  bar (&a);
}

then it is the same as:

struct A { int a; int b; int c; int d; };
void bar (void *);
void foo (void)
{
  struct A a = { .a = 21, .b = 0, .c = 0, .d = 0 };
  bar (&a);
}

	Jakub