Re: API parameter lengths

"
Hello Gene,

You wrote:
>Here's a case where the command line fails to pad blanks to 32 bytes.  I
>call the QSYRGFN API on V4R4 like this from the command line to register a
>30-character function named XYZ:

The QSYRGFN program looks like a C program.  That changes the rules.  See 
the excerpt below from the CL Programming Guide.

>This creates a function named 'XYZ' + X'00' + 26 blanks.  Huh?  Why did 
>the command line insert a trailing null after 'Z'?  Is this a feature?  

The CALL command is looking at the target program and NULL terminates the 
string because that is probably what a C program expects.  The assumption is 
wrong in this case because QSYRGFN has no length value associated with the 
Function ID and since the documentation does not state a NULL terminator is 
required the API expects 30 characters padded with blanks.  You can also 
infer this from the function prototype in qsyrgfn.h and qsyrgfn1.h which 
define the first parameter as char[30] rather than a pointer to a null 
terminated string.

>Now I call the QSYRGFN API like this from the command line and explicitly 
>pad the first parameter to 32 blanks:
>This creates a function named 'XYZ' + 27 blanks, as I expected.  

You'll probably find that the 33rd byte is a NULL character in which case 
CALL is behaving consistently.

>Somehow
>the QSYRGFN API can determine whether the command line caller typed a
>3-character string or a 32-character string in parameter one.  Can an MI
>program determine this information, too?

Here is the relevant passage from the CL Programming Guide.

� An exception to the previous description is when the CALL command calls an
� ILE C/400 program. When using the CALL command to call a C/400 program and
� pass character or logical constants, the system adds a null character
� (x'00') after the last non-blank character. If the constant is a character
� string that is enclosed in apostrophes or a hexadecimal constant, the null
� character is added after the last character that was specified. This
� preserves the trailing blanks (x '40' characters). Numeric values are not
� null-terminated. See the IBM SAA C/400 User's Guide, SC09-1347 for more
� information.

Regards,
Simon Coulter.

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