[fpc-devel] Passing consts to const

[David Butler]

On Tue, 07 Jun 2005 19:59:56 +0200, you wrote:

>David Butler wrote:
>> {$WRITEABLECONST OFF}
>> 
>> procedure TestBuf(const Buf; Size: Integer);
>> begin
>> end;
>> 
>> const A : Byte = 1;
>
> From this point A is treated as a normal variable with an initial 
>assignment...
>
>> 
>> begin
>>   TestBuf(A, 1);
>
>... so it is not const here.

It is perfectly legal to pass a "var" to a "const". The problem is
that FPC thinks we are trying to change A.

>
>Guess if you would substitute the line
> > const A : Byte = 1;
>with
> > const A = 1;
>
>It should work. AFAIR, typed constants are treated exactly as variables 
>with an initial value.

Exactly. If it is treated like a normal variable, why the error
message?

The problem is not with the "const A" declaration, the problem is with
the the call to TestBuf not allowing a "constant variable" to be
passed (like Delphi rightly does).

Although the TestBuf call compiles with your suggested "const A = 1"
declaration in FPC, it doesn't make sense (and it rightly doesn't
compile in Delphi).

I don't want to say FPC should be doing everything the way Delphi
does, but in this case it makes sense, in my opinion.

Regards
David