Re: Retrieving a Pointer to an Object

[Tim McCarthy <twmac@xxxxxxxxxxxxxx>]

Simon,
I fear you have not been long coding in C. The very "unintelligent" ptr++;
is probably the most common C statement I can think of beside 'if'. Hey,
most C examples even call their pointers 'ptr'. If you have a better way of
parsing a string then legions of C programmers would love to hear from you.

I understand what you're saying about using IBM API structures and offsets
but you completely missed the point I was making which had nothing to do
with these API's. Pointer arithmetic (which goes beyond simple
incrementing) is an essential part of any good programming language. I'm
very familiar with using supplied offsets to position to information
structures and I don't believe I was proposing anything else. But thank you
for the "re-fresher" anyway. 

At 11:19 PM 6/26/98 +1000, you wrote:
>Hello Tim,
>
>I fear I am about to get shot again but ptr++ is a very unintelligent way
of incrementing a pointer.  It may 
>be fine in code for which you own all the parts but it will bite you if
you do that with structures owned by 
>someone else.  For example many of the SPI APIs return information to a
space described by a structure.  The 
>common C language technique of incrementing a pointer to the structure
will break when IBM increases the 
>amount of information returned in that structure.  This is because the
pointer is incremented by the declared 
>size of the structure so if the amount of data returned is greater than
the structure your code will break.  
>Recompiling (to pick up the new structure) is the minimum required fix.
The correct approach is to increment 
>it by the amount of returned data and so remove release dependencies.  Of
course the interface/structure must 
>be designed to provide the amount of returned data.
>
>Regards,
>Simon Coulter.
>
>//----------------------------------------------------------
>// FlyByNight Software         AS/400 Technical Specialists
>// Phone: +61 3 9419 0175      Mobile: +61 0411 091 400
>// Fax:   +61 3 9419 0175      E-mail: shc@flybynight.com.au
>// 
>// Windoze should not be open at Warp speed.
> 
>
>//--- forwarded letter
-------------------------------------------------------
>> X-Mailer: Windows Eudora Light Version 3.0.1 (16)
>> Date: Thu, 25 Jun 98 15:37:26 +1000
>> From: "Tim McCarthy" <twmac@mindspring.com>
>> To: MIDRANGE-L@midrange.com
>> Reply-To: MIDRANGE-L@midrange.com
>> Subject: Re: Retrieving a Pointer to an Object
>
>> 
>> Yes I am on the wrong ILE RPG release - glad to hear it's changed. I
>> completely disagree though that pointer math is pretty horrible at the best
>> of times. Show me a simpler construct than ptr++;
>> 
>> At 12:46 PM 6/25/98 -0400, you wrote:
>> >
>> >Well pointer arithmetic is pretty horrible at the best of times, but if
you
>> >think it's worse in RPG than in other languages you're just not on the
right
>> >release!  Pointer math was introduced in V3R7.
>> >
>> >Jon Paris - AS/400 AD Market Support - paris@ca.ibm.com
>> >Phone: (416) 448-4019   -   Fax: (416) 448-4414
>> 
>> 
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