Re: Math Bindable API

[bmorris@xxxxxxxxxx]

>Date: Tue, 4 Apr 2000 17:31:24 -0400
>From: ajkumar@rccl.com
>
>If I have to use the Math Bindable API's CEESSCOS and CEESSSIN as a
>procedure that returns a value, do I have to pass mandatory as well as
>optional parameter all the time.
>
>
>When I used the first approach the program worked fine for the first time.
>But, everytime I compile and then call the program, the program bombs with
the foll. errors
>Pointer not set for location referenced.
>Unexpected user error occurred in CEESSSIN.
>
>Strangely enough, the program seems to work in debug mode!!

Ajith, the parameter is not optional; it is "omissible" which
means you may pass *OMIT.  The reason this works sometimes and
crashes other times is that CEESSSIN is assuming you have passed
the parameter and is accessing the place where the parameter
would be.  How it behaves depends on what happens
to be at that place:
a. not a pointer, CEESSSIN assumes an omitted parameter - this is fine
b. a valid pointer, CEESSSIN puts feedback where the pointer points to
   - this is very bad - this can cause problems later in your code or
     in some other code, depending on what storage gets corrupted
c. a pointer of some type that CEESSSIN doesn't like - this is the
   scenario that causes CEESSSIN to crash.

Using the debugger causes the parameter stack to contain different
values, so it is not surprising that this behaves differently in
the debugger.

I just read a second posting of yours on this subject.  You were asking
why using CALLB with the result in the second parameter gave you good
results while using EVAL with a return value gave wrong results.  This
procedure can only be called the way it is intended to be called.  If
a parameter is listed as an output parameter, it must be passed as a
parameter; it cannot be received as a return value.

Here is a correct prototype (use a similar one for any CEE math function
with 1 input parameter):

d Cos             pr                  extproc('CEESDCOS')
d  input                         8f   const
d  result                        8f
d  FeedBack                     12    options(*OMIT)

CALLP    Cos (0E0 : result : *OMIT)

If you use CALLB, you must pass a third parameter of *OMIT.  It is only
working now by accident.

If you want to use math functions as procedures returning a value, you
can do as Paul Cunanne suggested, and write your own wrapping procedure
for this, or you can call the C functions 'sin', 'cos' etc.  If you use
these, you need binding directory QC2LE.

d Cos             pr                  extproc('cos')
d  input                         8f   value

Barbara Morris


+---
| This is the RPG/400 Mailing List!
| To submit a new message, send your mail to RPG400-L@midrange.com.
| To subscribe to this list send email to RPG400-L-SUB@midrange.com.
| To unsubscribe from this list send email to RPG400-L-UNSUB@midrange.com.
| Questions should be directed to the list owner/operator: david@midrange.com
+---