Re: class *obj = new class;

From:

James Kanze <james.kanze@gmail.com>

Newsgroups:

comp.lang.c++

Date:

Sun, 4 Jul 2010 04:22:16 -0700 (PDT)

Message-ID:

<8bbe6afc-3c5a-486f-8715-9ded3b1837f6@a30g2000yqn.googlegroups.com>

On Jul 2, 11:46 am, "Bo Persson" <b...@gmb.dk> wrote:

_vjy wrote:

class class1 {};
class1 *obj = new class1;

is this valid syntax ? shouldn't this be like,

class1 *obj = new class1();

g++ gives no errors / warnings.

It doesn't matter much in your example. The first one will be
default initialized, while the second is value initialized.
For an empty class object, there is no difference.

On the other hand

int* one = new int;
int* two = new int();

will cause 'one' to point to an uninitialized int, while 'two' points
to an int that is zero.

If you have a class object with a constructor, the constructor
will be called in both cases.

There's no such thing as a class type without a constructor. If
the class has a trivial default constructor (the one provided by
the compiler), on the other hand, the distinction you mention
holds, with default initialization leaving members of built-in
types uninitialized, and value initialization zero-initializing
them.

--
James Kanze