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From: levi@localhost.nc3a.nato.int
Subject: Memory leak
Date: 25 Sep 2001, 14:27:55

On Tue, 25 Sep 2001, Frank Heckenbach wrote:

> There is a known problem. Some operations (esp. string
> concatenation) need temporary storage (on the stack) which isn't
> freed immediately, so it will accumulate in loops. A trivial example
> follows.
>
> program Foo;
>
> var
>   s: String (100) = '';
>
> begin
>   repeat
>     s := s + ''
>   until False
> end.
>
> I think we know the cause of the problem (alloca_string if anyone
> cares) and therefore can fix it soon.
>
> The only know work-around for know is to move the loop body into a
> subroutine. That's not nice, but if it works, you can at least be
> quite sure it's this problem you see.

That was part of my problem. If I modify my code in this style:

program Foo;

var
   s: String (100) = '';

procedure loop;

begin
    s := s + ''
end;

begin
  repeat
   loop;
  until False
end.

it is not growing that fast any more. (In fact, for this particular example
it is not growing at all.) For that I had to move all the string
operations behind a procedure (i.e. concat, writestr and readstr).
However it is still growing a bit. Could that caused by the calls of the
"random" function in the program?


Cheers,

miklos

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