RE: Prototyping printf()

[Joel Fritz <JFritz@xxxxxxxxxxxxxxxx>]

I may be missing something, but I think it hinges on the conveniently(?)
ambiguous way strings work in C  and printf()'s being a function with a
variable argument list.  Even though strings are pointers in C, there are
situations, like printf(), where you can use them like the numeric data
types. 

I would be surprised and gratified if there were a way to do it, but I think
you've hit on something where there is no common ground between the two
languagages.  

BTW, how are you using printf() in RPG?  Is it CGI?   

> -----Original Message-----
> From: Simon Coulter [mailto:shc@flybynight.com.au]
> Sent: Saturday, September 23, 2000 5:46 PM
> To: RPG400-L@midrange.com
> Subject: Prototyping printf()
> 
> 
> 
> Hello all,
> 
> Now here's an interesting exercise that is rapidly becoming 
> one of futility.
> 
> printf() is a C function that expects a format string 
> followed by zero or more 
> substitution values.  The substitution arguments can be any 
> of C's supported data types 
> and are passed by value.  Prototypng it for known data types 
> is easy but the real point 
> is to create a single definition that can handle all data 
> types.  A sample prototype of 
> the form:
> 
> D printf      PR                      10I 0  EXTPROC('printf')
> D  formatString                                 *    VALUE 
> OPTIONS(*STRING)
> D  arg1                                       10I 0  VALUE 
> OPTIONS(*NOPASS)
> 
> will allow dynamic printing like:
> 
> C             EVAL    rc=printf('The number is %i ' : anInt)
> 
> however if I then want to print a string I need a separate 
> prototype with arg1 defined 
> appropriately.
> 
> D printf      PR                      10I 0  EXTPROC('printf')
> D  formatString                                 *    VALUE 
> OPTIONS(*STRING)
> D  arg1                                         *    VALUE 
> OPTIONS(*STRING:*NOPASS)
> 
> and then I can:
> 
> C             EVAL    rc=printf('The string is %s ' : aString)
> 
> and so we go on with additional prototypes for each possible 
> variation of substitution 
> arguments.
> 
> My question (to which I think the answer is NO) is:  Is it 
> possible to define an RPG 
> prototype describing printf() in its native form?
> 
> The difficulty seems to hinge on C's requirement for passing 
> by VALUE and RPGs 
> requirement for knowing the data type up front.  The closest 
> I can come to allowing RPG 
> to accept anything is by using a prototype like:
> 
> D printf      PR                      10I 0  EXTPROC('printf')
> D  formatString                                 *    VALUE 
> OPTIONS(*STRING)
> D  arg1                                         *    VALUE 
> OPTIONS(*NOPASS)
> D  arg2                                         *    VALUE 
> OPTIONS(*NOPASS)
> D  arg3                                         *    VALUE 
> OPTIONS(*NOPASS)
> D  arg4                                         *    VALUE 
> OPTIONS(*NOPASS)
> 
> which allows RPG to successfully compile statements such as:
> 
> C             for     count = 0 to 10 by 2
> C             EVAL    rc=printf('%s %i' : %addr(string) : 
> %addr(count) )
> C             endfor
> 
> When it runs the string is printed successfully but the 
> integer is not because it is the 
> VALUE of the ADDRESS of the integer that is being passed not 
> the VALUE of the integer.  
> And that leads us back to a prototype like:
> 
> D printf      PR                      10I 0  EXTPROC('printf')
> D  formatString                                 *    VALUE 
> OPTIONS(*STRING)
> D  arg1                                         *    VALUE 
> OPTIONS(*STRING:*NOPASS)
> D  arg2                                       10I 0  VALUE 
> OPTIONS(*NOPASS)
> 
> Aaaarrrrrggghhhh!!!!
> 
> Regards,
> Simon Coulter.
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