[fpc-pascal] which "managed" result types require extra work?

Michael Van Canneyt michael at freepascal.org
Tue Jun 28 20:05:54 CEST 2016



On Tue, 28 Jun 2016, J├╝rgen Hestermann wrote:

> Am 2016-06-28 um 01:13 schrieb David Emerson:
>> The source of my confusion -- and I suspect that of many others -- is that 
> I always assumed a function result was treated like a local variable within 
> the function, rather than a parameter to the function.
>> Since managed types are automatically initialized when they are local 
> variables, I assumed a function result was the same.
>> Unfortunately, the documentation does not make this sufficiently clear in 
> describing managed types. I guess I should file a documentation bug.
>
> Exactly my opinion too.
> Especially, because it behaved differently with Free Pascal versions prior to 
> 3!
>
> And it does not behave like a function parameter, it behaves like a *var* 
> parameter.
> All other types of parameters behave differently!
> And while a var parameter can *only* be assigned to a variable (so that it is 
> clear
> that an existing variable is used) a function result can also be used in an
> expression which makes it silently mutate into a global variable! What a 
> mess!
>
> And for local variables I can easily set a default value in the declaration 
> but not for the function result.
> I have to remind me not to forget this in the code.

This has been so since day 1 in Pascal.

Any behaviour other than that was entirely coincidental.

Michae.


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