Is there a simple way to tell if slTest has been assigned in the following ?

(without specifically assigning it to NIL in the declaration)

var
   slTest 	:TStringList;
begin
   if Assigned(slTest) then FreeAndNil(slTest); // gives exception
end;

Thanks - SteveG

Shall do - Thanks for that

When slTest is a local variable, you should initialize it to Nil. Otherwise the variable contains garbage, that most probably is *not* Nil, so that FreeAndNil tries to free something that never has been created.

DoDi

Just to be clear

Initialize it in code not in the declaration, since in the declaration afaik that makes it a static variable instead of a truely local one, even when declared with local scope.

You can only initialize a global variable. For "initialized local variables" you need to use writable "constants" ;)

Regardts,
Sven

2011/4/25 Marco van de Voort :

procedure Test;
var
  i: Integer = 0;
  p: Pointer = nil;
  t: TObject = nil;
begin
end;

These are not local variables? If not, what are the consequences of them being static variables? I assume it is worse, since you recommend otherwise.

2011/4/25 Marco van de Voort :

Initialize it in code not in the declaration, since in the declaration afaik that makes it a static variable instead of a truely local one, even when declared with local scope.

Hmm... are you sure?

program project1;
{$mode objfpc}{$H+}
procedure print(num: Integer);
begin
  writeln(num);
end;
procedure foo(cnt: Integer {-4});
var
  x : integer = 0;    {-8}
  y : integer;        {-12}
begin
  print(x);
  print(y);
  inc(x);
  inc(y);
  if cnt < 5 then begin
    foo(cnt + 1);
  end;
end;
begin
  foo(0);
end.

compiled with FPC 2.4.2

P$PROJECT1_FOO$LONGINT:
pushl %ebp
movl %esp,%ebp
subl $12,%esp
movl %eax,-4(%ebp)

movl TC_P$PROJECT1_FOO$LONGINT_defaultx,%eax
movl %eax,-8(%ebp)

movl -8(%ebp),%eax
call P$PROJECT1_PRINT$LONGINT
movl -12(%ebp),%eax
call P$PROJECT1_PRINT$LONGINT

incl -8(%ebp)
incl -12(%ebp)

movl -4(%ebp),%eax
cmpl $5,%eax
jl .Lj23
jmp .Lj24
.Lj23:
movl -4(%ebp),%eax
incl %eax
call P$PROJECT1_FOO$LONGINT
.Lj24:
leave
ret

output:
0
2
0
134512851
0
134512851
0
134512851
0
134512851
0
134512851

Bernd wrote

> that makes it a static variable instead of a truely local one, even when declared > with local scope. Hmm... are you sure?

Then, yes. Now, no :-)

I assumed it was the same as the const variant.