Error: constant false is not an lvalue

[Rainer Deyke]

Jarrett Billingsley wrote:
> Although teeeeeeechnically speaking that would be illegal code. The D
> spec says that it's not legal to use the value of uninitialized
> variables. Default initialization is kind of a poor man's substitute
> for actual flow control which determines that. By relying on default
> initialization, you're relying on what is actually nonconformant
> behavior, and it could be broken in the future or by a smarter
> compiler.

No.  This is an uninitialized variable in D:

  int i = void;

This is an initialized variable in D:

  int i;

A default-initialized variable is not in any way less initialized than
any other initialized variable.

Flow control can add two things to D.  It can turn this:

  int i = <value>;

or, equivalently, this:

  int i;

into this:

  int i = void;

whenever it is safe to do so.  It can also turn this:

  int i = void;

into an error message if it can prove that this is /not/ safe.

It cannot ever alter the behavior of the following perfectly legal D
function:

  int get_zero() {
    int i;
    return i;
  }


-- 
Rainer Deyke - rainerd at eldwood.com