Hi

The following code snippet gives a compile error: "Error: Can't assign values to const variable".

It should be legal, since we are passing a const to a const parameter.

It should only give that error if TestBuf was declared as "var Buf" instead of "const Buf".

Regards
David

{$WRITEABLECONST OFF}
procedure TestBuf(const Buf; Size: Integer);
begin
end;
const A : Byte = 1;
begin
  TestBuf(A, 1);
end.

From this point A is treated as a normal variable with an initial assignment...

begin TestBuf(A, 1);

... so it is not const here.

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.

Actually untyped parameters accept anything except numeral or untyped numeric constant in Delphi. The meaning of const in this example is contract that function will not change passed value.

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

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

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.

Please report bugs/compatibilities to the bugs repository. Bugs posted on the mailing list tend to be forgotten.

Added. Thanks Peter.

And fixed already! Kudos to you :)