[fpc-pascal]Constructor failing...

Anton Tichawa anton.tichawa at chello.at
Fri Mar 21 17:46:23 CET 2003

On Friday 21 March 2003 12:29, you wrote:
> >> > But, when I use fail in my simple example program, it returns
> >>
> >> NIL okay but
> >>
> >> > the Heaptrace function tells me I have two unfreed memory blocks (36
> >> > bytes).
> >> > I can't see a memory leak anywhere else in that program, what
> >>
> >> could cause
> >>
> >> > this? (Heaptrace output is as follows: I am using FPC 1.0.6 btw)
> >>
> >> [snip heap dump]
> >>
> >> That is the exception frame that is left on the heap. I don't have the
> >> time to analyze what the cause is that the exception frame is not
> >> removed.
> >
> > It may be a bug in 1.0.6 which has subsequently been fixed. I downloaded
> > and
> > installed the 1.1 snapshots and compiled the same source code, and the
> > memory leak vanishes....
> The reason why 1.1 has no leak is that it uses the stack to store the
> exception frames. The real problem is still there, because exception stack
> is still not updated

some months ago i had a discussion with a friend, converning global (static, 
absolute) variables. his point of view was that they're not necessary when 
using oop; mine was, sometimes they're absoulutely necessary.

if we have just one level of exception processing above normal program 
execution (i. e. while an exception is being processed, no other exception 
will gain control), we can use absolute variables for the exception frame.

it's even possible to define a fixed whole number of exception layers and 
allocate absolute memory for N exception levels.

that memory space would not get lost, as it can be saved by allocating the 
'normal' stack or 'normal' heap more tightly - the old system has to reserve 
exception spae implicitely on the stack or on the heap.

what do you think about that?



"Adas Methode war, wie sich zeigen wird, Tagträume in offenbar korrekte 
Berechnungen einzuweben."

Doris Langley Moore: Ada, Countess of Lovelace (London 1977).


Anton Tichawa
Volkertstrasse 19 / 20
A-1020 Wien
mobil: +43 664 52 07 907
email: anton.tichawa at chello.at


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