Re: Correct use of STATIC variables

<snip>I don't find many uses for it, to tell the truth.<snip>

Two examples of stateful routines:

A program that reads lines from a source file and 'feeds' the lines to a
parser routine. The parser routine either:
- starts a new statement, or
- parses the previous statement and starts a new statement, or
- adds the line to the current statement, or
- parses the last statement.

Another program reads items from up to 5 files (same file in different
libraries). To the mainline it is like reading one file; the reading
routine returns eiter EOF or a data structure. In order to know which file
to read and which data to return the reading routine has to maintain state
of all files (eof, current key, current data).

Joep Beckeringh

Vern Hamberg

David

I think the point of STATIC variables is, you DON'T initialize them
between program calls. At least, not according to this description from
the RPG Reference on static variables. I mean, how do you initialize
something that is not visible outside of its context, such as a

procedure?

=================================================================
Local definitions use automatic storage. *Automatic storage* is storage
that exists only for the duration of the call to the procedure.
Variables in automatic storage do not save their values across calls.
Global definitions, on the other hand, use static storage. *Static
storage* is storage that has a constant location in memory for all calls

of a program or procedure. It keeps its value across calls.
Specify the STATIC keyword to indicate that a local field definition use

static storage, in which case it will keep its value on each call to the

procedure. If the keyword STATIC is specified, the item will be
initialized at module initialization time.
Static storage in the main procedure is subject to the RPG cycle, and so

the value changes on the next call if LR was on at the end of the last
call. However, local static variables will not get reinitialized because

of LR in the main procedure.
=================================================================

My first question is, what are you trying to accomplish when you use the

STATIC keyword? I don't find many uses for it, to tell the truth. There
is the idea of thread-local storage - this is a separate copy of the
variables for a procedure that is called in different threads of a job.
If you are using it for performance reasons, to avoid initializing the
storage on each call, that is a waste of development time, in most
cases. Someone once said that the 3 rules of optimization are "Don't!
Don't! Don't!" At least not down to the most minute level.

So it'd help to know why it is being used - even things like counters
can be handled with parameters instead of static variables.

I believe the scratchpad of SQL functions can be static storage - but
does not need to be, apparently. Just looked it up!!

HTH
Vern