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  2. RPG400-L
  3. January 2007

Re: seconds since 1601


On 16/01/2007, at 2:25 AM, Joe Pluta wrote:
Simon, couldn't you also pass a pointer by value and explicitly set it to 
*NULL?
Yes, but then you'd have to define the prototype as accepting a pointer for this parameter and then you'd have to use %ADDR(feedback) if you actually wanted the feedback information. Requiring an RPG caller to mess with %ADDR on a procedure call seems incorrect to me. It is far more natural for RPG to specify scalar names rather than pointer names. Also, the documentation says use *OMIT for omissable parameters so using *NULL or a null pointer could be confusing to the next programmer.
In any case all the LE APIs expect parameters passed by reference and although we know that a pointer-by-value is the same as a scalar-by-reference this trick should be reserved for when there is no alternative.
Note also that some LE APIs expect a pointer-by-reference (e.g., the token parameter for CEEHDLR) and I think an RPG programmer would find it confusing to sometimes pass the address of a scalar and other times pass the address of a pointer. Consistency in defining prototypes for these APIs is the key to using them successfully.
There are a few cases where an API can handle a buffer larger than the 32K or 64K maximum named scalar size supported by RPG and for these %ADDR is the only option but in many/most cases that is the exception and I prefer to define a CONST scalar in prototypes even if the C version defines a pointer-by-value. Makes it much easier to use from RPG. 

Regards,
Simon Coulter.
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