Re: passing parameters longer than expected

[Scott Klement <rpg400-l@xxxxxxxxxxxxxxxx>]

Hi Dave,

I'm a bit lost.  What problem did this cause for you, exactly?

Passing a parameter that's too long won't hurt anything.  Granted, the 
routine you've called won't be able to access anything past it's 
declared length -- but other than that, it shouldn't cause a problem.

Prototypes are intended to protect against the opposite problem: 
Passing data that's too short.  Such as when a caller has a 45A and 
calls a procedure/pgm where the parm is declared as 100A.  This is 
downright dangerous, because the called routine will potentially 
read/write memory that doesn't belong to the caller's variable (because 
it's accessing data past the allocated spot in memory.)  If you use 
CONST, RPG "fixes" the problem by declaring a larger space, and copying 
the 45A to 100A, so there's no danger (and therefore no reason to signal 
an error.)

But, the problem you describe, where the caller's variable is too long 
doesn't pose any risk of memory corruption.  It can't access the whole 
variable, but the part that it does access is still within the bounds of 
the caller's variable, and therefore safe to use.

So I'm surprised by how you say this "bit you" and that you wish the 
system would warn you?  What problem does it cause?




On 3/23/2012 6:22 AM, Dave wrote:
> Hi, all,
> I think this subject has been well debated in the past, but I just got
> bitten again and would like to know how to protect myself in the
> future. I copied and adapted some code and did not realise until well
> into testing that I was passing a 100A parameter to a procedure
> expecting 45A. I believe that when CONST is specified, the compiler
> converts the parameter and there is no warning. I'm still wondering
> why as I think that prototyping was introduced in order to protect one
> against this sort of error. Now I discover that many other procedures
> are doing the same call and I have to analyze to see if I can just go
> ahead and change the 45A parameter to 100A