Re: declaration vs. defintion

From: Alwyn (dt015a1979_at_mac.com.invalid)
Date: 11/01/04 

Date: Mon, 01 Nov 2004 12:26:53 +0000

In article <2ummi2F2bqr3qU1@uni-berlin.de>, Val \
<chrisval@bigpond.com.au> wrote:
>
> AFAIU, when we say we have *defined* something, doesn't
> that imply that storage is associated with the particular
> identifier being defined ?,

You shouldn't think of it in terms of storage being allocated. Just
think of a definition as a specification that is sufficiently complete
to be used in a program.

Take for instance:

const int Five = 5;

inline int timesFive(int n)
{
   return n * Five;
}

There is no need for there to be storage associated with either Five or
timesFive, yet they have been defined, and they are usable, no?

> therefore meaning that once we
> have a definition of an object, we cannot define it again ?,
> hence the ODR ?

I believe the one-definition rule goes something like this:

A translation unit must not contain more than one definition of any
variable, function, class type, enumeration type, or template, and
external definitions must not be redefined within a program.

A user-defined type is not an object and is not included in the above
list.

Alwyn

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