Re: Using STATIC

[Barbara Morris <bmorris@xxxxxxxxxx>]

Joe Pluta wrote:
> ...
> There are other reasons to return a pointer to private storage.  Again, I'm
> talking in general terms rather than specifically in RPG terms, but it is
> much easier (and faster) to compare two pointers to structures rather than
> to compare the entire contents of the structure.  Let's say a method is
> designed to return one of several structures.  It can either create a new
> clone of the structure each time, or a pointer to an internally defined
> structure.  If this method always returns a pointer to a specific internally
> defined structure, a programmer may use a much more efficient pointer
> comparison to determine equality.

It's even faster, and just as easy, to compare two handles to
structures.  The service can communicate with its consumers by say an
integer that's an index into an array of pointers. You still have the
quick comparison without the consumer having the ability to look inside
(or worse, change) the private structure.  (A real handle would probably
be an encoding of some unique value plus an array index, to prevent
accidental reuse.)

> Anyway, my point is that determining whether a given technique is "right" or
> "wrong" really depends upon the implementation and the reason.

No argument there.  But as a rule of thumb, giving out a pointer to a
module's private storage can lead to hard-to-solve problems, like the
one that started this thread.

By the way, speaking of "thread", two modules having stored pointers to
one module's static storage is one of the thread-safety issues that
RPG's THREAD(*SERIALIZE) doesn't protect you against  In a thread-safe
application, you would have to add your own serialization to access that
shared storage.