Re: type qualifiers on function return types?

["Nate Jenkins" <nate@uniwest.com>]

>> I am sure I am not the only one here wondering what "type qualifiers" 
>> are.
>> Could someone expound on what they are and why one would use them?
>
> My DEC C Compiler documentation gives a good intro to type qualifiers.
> Here is what is says:
>
> There are four type qualifiers:
>
>    * const
>    * volatile
>    * __unaligned (axp)
>    * __restrict (pointer type only) [now: restrict]
>
> "Type qualifiers were introduced by the ANSI C standard to, in part,
> give you greater control over the compiler's optimizations. The const
> and volatile type qualifiers can be applied to any type. The
> __restrict type qualifier can be applied only to pointer types.
>
> Note that because the __restrict type qualifier is not part of the
> 1989 ANSI C standard, this keyword has double leading underscores. The
> next version (9X) of the C standard is expected to adopt the keyword
> restrict with the same semantics described in this section.
>
> The use of const gives you a method of controlling write access to an
> object, and eliminates potential side effects across function calls
> involving that object. This is because a side effect is an alteration
> of an object's storage and const prohibits such alteration.
>
> Use volatile to qualify an object that can be changed by other
> processes or hardware. The use of volatile disables optimizations with
> respect to referencing the object. If an object is volatile qualified,
> it may be changed between the time it is initialized and any
> subsequent assignments. Therefore, it cannot be optimized."
>
> I hope this info was useful enough.
>
> \Steve
>
> PS: Please do not top post.  Thanks.
>
> --
>
> Steve Graegert <graegerts@gmail.com> | Blog <http://tikomi.org>
> Software Consultant {C/C++ && Java && .NET}
> Office: +49 9131 7123988
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>
>

Thanks for the info Robert and Steve.  Sometimes I forget the fancy names of 
these things.  Yes, "const" is probably the most commonly used one...

Nate