Clearing a structure - syntax s = {0} question

[int2str]

Hi!

Inspired by a recent thread on this list, I'd like to ask the
following:

Given this code:

struct S
{
int a;
int b;
int c;
}

...

S s = {0};

How does this work? I mean it does clear the whole struct (at least
everywhere I tried), but what language feature causes this to happen?

Also, would this safely work for this struct S2?

struct S2
{
int a;

virtual void f();
}

Thanks,
Andre

[roberts.noah]

in*****@gmail.com wrote:

Hi!

Inspired by a recent thread on this list, I'd like to ask the
following:

Given this code:

struct S
{
int a;
int b;
int c;
}

...

S s = {0};

How does this work? I mean it does clear the whole struct (at least
everywhere I tried), but what language feature causes this to happen?
Structures like arrays and structs can be initialized by providing
partial data. The rest of the variable is filled with 0 (no matter
what arch or value of 0). "0" is guaranteed to be 0 for any type and
the initialization is recursive. The {0} above could be anything but
the first item would be initialized with whatever you provide. I don't
believe any other number would work for some types while the number 0
does.

Also, would this safely work for this struct S2?

struct S2
{
int a;

virtual void f();
}

It at least doesn't work over here. Having a virtual function creates
a "non-agrigate" type and this can't be initialized with {0}.