Question

WCHAR wszFoo[CONSTANT_BAR] = {0}; 

I’ve never seen something like {0} used in C++ as part of the language. And I have no idea how to search for a question like this online. What is it?

Answer 1

$8.5.1/7 –

“If there are fewer initializers in
the list than there are members in the
aggregate, then each member not
explicitly initialized shall be
value-initialized (8.5).”

All this means, is that there is an explict request to initialize first element to 0. Since initializers are not specified for the remaining elements, they are value-initialized. This in case of WCHARs means are initialized to 0.

What does value initialized means? Here is what the Standard says in $8.5 (italics are mine)

To value-initialize an object of type
T means:

— if T is a class type
(clause 9) with a user-declared
constructor (12.1), then the default
constructor for T is called (and the
initialization is ill-formed if T has
no accessible default constructor);

—
if T is a non-union class type without
a user-declared constructor, then
every non-static data member and
base-class component of T is
value-initialized;

— if T is an array
type, then each element is
value-initialized;

— otherwise, the
object is zero-initialized <——
WCHAR will fit here

To zero-initialize an object of type T
means:

— if T is a scalar type (3.9),
the object is set to the value of 0
(zero) converted to T; <—— WCHAR
will fit here

— if T is a non-union
class type, each nonstatic data member
and each base-class subobject is
zeroinitialized;

— if T is a union
type, the object’s first named data
member89) is zero-initialized;

— if T
is an array type, each element is
zero-initialized;

— if T is a
reference type, no initialization is
performed.