On 11.09.2017 11:46, Ryan Joseph wrote:
>
>> On Sep 11, 2017, at 4:20 PM, Sven Barth via fpc-pascal
>> <fpc-pascal@lists.freepascal.org> wrote:
>>
>> They're used for the reference counter of the array (or string or
>> interface). The reference counter changes each time you assign an array or
>> pass it to a by-value parameter or if you change a value (cause the
>> compiler/RTL needs to make sure that the reference to the array is unique
>> then).
>>
>>
>
> Maybe this is relevant to my poor performance then but perhaps it’s just the
> way the time profiler works? It’s telling me the program is spending 16% in
> system_delocked which seems extreme.
>
> See if I have a dynamic array and call arr[0] := xxx then those functions
> will be called (or FPC_DYNARRAY_ASSIGN)? I also have a dynamic array in an
> object which is passed a function parameter, but not by value so that doesn’t
> fit your description.
I've rechecked and the thing is as follows:
- the IncLocked call happens each time you assign a dynamic array to
another dynamic array variable or a by-value parameter (this also
includes being part of a record, but not a class instance or TP-style
object)
- the DecLocked call happens each time the array is cleared (as long as
the reference count is > 0 this only means a decrement of the count)
which happens if you assign Nil, assign a different array (the
destination array is "cleared") or if the array variable goes out of scope
The two routines are also used in context of Ansi- and UnicodeString
variables as well as reference counted interfaces (aka COM-style
interfaces).
In contrast to what I wrote earlier the compiler does however not ensure
a unique array if you only change an element, so given the following
example:
=== code begin ===
program tarrtest;
procedure Test(aArg: array of LongInt);
var
i: LongInt;
begin
for i in aArg do
Writeln(i);
end;
var
ia1, ia2: array of LongInt;
begin
ia1 := [1, 2, 3];
ia2 := ia1;
ia1[1] := 5;
Test(ia1);
Test(ia2);
end.
=== code end ===
The output will be
=== output begin ===
1
5
3
1
5
3
== output end ===
Regards,
Sven
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