On Sun, Jan 10, 2021 at 12:09 PM Sven Barth via fpc-pascal
<fpc-pascal@lists.freepascal.org> wrote:
> If after the Move only one of the two references is reachable anymore
> (because e.g. some internal count variable "ends" the array before that
> element) then you don't need to care about increasing the reference
> count, cause there is only one reference after all (in that case you
> must *not* use an assignment to clear the value, but e.g. FillChar,
> cause the reference count must not be touched). Only if you'd really
> duplicate the element you'd need to take care of that.
I came up with this:
Assume that:
FData is defined as Array of T (T being generic)
procedure MoveDataManaged(StartIndex: SizeUInt; Offset: SizeInt;
NrElems: SizeUInt);
var
i: SizeUInt;
begin
if Offset>0 then
begin
for i := StartIndex + NrElems-1 downto StartIndex do
begin
if IsManagedType(T) then //finalize before overwriting
Finalize(FData[i+Offset]);
FData[i+Offset] := FData[i];
if IsManagedType(T) then
Finalize(FData[i]);
FillChar(FData[i], SizeOf(T), 0); //erase old data, not
necessary after finalize
end;
end
else
begin
for i := 0 to NrElems-1 do
begin
if IsManagedType(T) then
Finalize(FData[StartIndex+i+Offset]);
FData[StartIndex+i+Offset] := FData[StartIndex+i];
if IsManagedType(T) then
Finalize(FData[StartIndex+i]);
FillChar(FData[StartIndex+i], SizeOf(T), 0);
end;
end;
end;
I tested this with T being Array of Char (so FData being an array of
array of Char).
Leaving out any of the Finalize statements will make HeapTrace barf at
me about unfreed memory blocks.
Does it make any sense?
--
Bart
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