🚀 go-pugleaf

In article <1992Dec30.184614.5551@microsoft.com> (Jim Adcock) writes:
> Can you define your terms for us?

> "distinct objects" means what?
It means the objects are not identical.  

I was going to say that the standard for C++ needs to spell out what it
means for object to be identical in a better way than just by
     1. An object is a region of storage.
     2. A definition or a new expression reserves the storage
        needed by the object.
These two rules leave things much more loose than necessary when objects
require no storage.  But note that section 1.3 of the working paper 
(The C++ Memory Model) says:

	The constructs in a C++ program create, refer to, access, and
	manipulate objects in memory.  Each object (except bit-fields)
	occupies one or more contiguous bytes.

I missed this a while back when enumerating the features of the ARM and
working paper which supported
> The desired feature is:
>     Two pointers to the same type, which point to distinct objects
>     of that type, compare not equal.
This excerpt from 1.3 gives the general rule I was seeking, because
objects can be distinguished by the storage reserved for them.

The excerpt may raise a few questions.

	How much freedom does it leave a compiler to optimize away
	an object's bytes (by application of the "as if" rule, etc.)?
	I think a good deal of freedom, because the working paper
	doesn't define the results if a program attempts to refer to
	or manipulate the bytes of an object.

	Does it govern base class subobjects?  As I understand it,
	base class subobjects are objects, and hence are covered.

	Does it belong in the C++ standard?  I'd say yes, given that
	compilers will for many practical purposes be able to 
	optimize away unneeded bytes.

--
Prescott K. Turner, Jr.
Liant Software Corp. (developers of LPI languages)
959 Concord St., Framingham, MA 01701 USA    (508) 872-8700
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