[fpc-pascal] Argument evaluation order in Free Pascal and Delphi

[Dmitry Pribysh]

Hi,

 

As it is written in Free Pascal wiki, order of parameter evaluation is not defined in FPC, but it is defined in Delphi (Delphi guarantees left-to-right evaluation order).

However, when i compile my program with FPC in Delphi-mode (-Mdeplhi), arguments in function calls are evaluated in right-to-left order). And when i compile my program in ObjectFPC-mode (-Mobjfpc), i get the same behaviour.

I tested it on the following platforms (all got the same right-to-left evaluation order):

- ArchLinux x86_64, FPC 2.6.2.

- Archlinux i686, FPC 2.6.2

- Raspbian (Debian for Raspberry Pi) armhf, FPC 2.6.2.

 

So, is this a compatibility bug in FPC or i just got something wrong? And is there any way to force left-to-right parameter evalution order?

 

P.S. Minimal working example for testing parameter evaluation is attached to this email.

program main;

type
   TFoo = class
   private
      Next: Char;
   public
      constructor Create(initial: Char = 'a');
      function Bar: String;
   end;

constructor TFoo.Create(initial: Char = 'a');
begin
   Self.Next := initial;
end;

function TFoo.Bar: String;
begin
   Result := Self.Next;
   Self.Next := Char(Integer(Self.Next) + 1);
end;

procedure baz(s1: String; s2: String; s3: String);
begin
   writeln(s1, s2, s3);
end;

var
   Foo:  TFoo;
begin
   Foo := TFoo.Create;
   baz(Foo.Bar, Foo.Bar, Foo.Bar);
end.

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