Hello,
Instead of .Free in your FreeVars routine, you should use FreeAndNil(
theobject).
The correct lifecycle for class objects is :
var
anObject : TMyObject;
begin
anObject := nil; //not needed for class attributes. Required for local
function or global unit variables.
anObject := TMyObject.Create( params) //if an exception is raised here, the
anObject reference will still be nill.
try
//... do some code on anObject...
finally
FreeAndNil( anObject); //after this, the memory referenced by anObject is
freed, and the reference anObject is set to nil.
end;
end;
Hope this helps,
Thierry
----- Mail Original -----
De: "Frank Church" <vfcli...@gmail.com>
À: "FPC-Pascal users discussions" <fpc-pascal@lists.freepascal.org>
Envoyé: Samedi 22 Octobre 2011 09h08:17 GMT +01:00 Amsterdam / Berlin / Berne /
Rome / Stockholm / Vienne
Objet: Re: [fpc-pascal] How are Assigned, Free, Nil and Destroy related?
On 22 October 2011 07:20, Felipe Monteiro de Carvalho <
felipemonteiro.carva...@gmail.com > wrote:
I understand Assigned as being the same as <> nil, so Assigned(Object)
= Object <> nil
I vaguely remember that it could be safer in some corner case, but I
don't remember ever meting that.
Free is how you release the memory allocated for a object. Free calls
Destroy. Never call Destroy manually. When you implement the
destructor you always implement Destroy, never change Free.
Nil is not a routine, it is a value, it means that the object is
empty, it does not exist / is not allocated. Nil in existing
implementations that I know is represented by the value zero.
The typical life-cycle of a object is:
MyObject := TMyObject.Create;
try
MyObject.DoSomething();
finally
MyObject.Free;
end;
To implement this object you should implement Create, DoSomething and Destroy.
--
Felipe Monteiro de Carvalho
_______________________________________________
fpc-pascal maillist - fpc-pascal@lists.freepascal.org
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This code is the source of my woes. SCStrings and FBreakStrings are part of an
object. They are repeatedly used in a loop and I need to free the memory after
the loop runs or free the space taken up by their strings
type
TRuntimeMonitor = class(TThread)
private
Frequency: Integer;
IniFile: TMemIniFile;
SCStrings: TStringList;
FBreakStrings: TStringList;
procedure DispatchOutput;
procedure DisplayRawOutput;
protected
procedure Execute; override;
public
constructor Create(CreateSuspended: Boolean);
end;
procedure InitVars;
begin
if not Assigned(SCStrings) then
SCStrings := TStringList.Create;
if not Assigned(FBreakStrings) then
FBreakStrings := TStringList.Create;
IniFile := TMemIniFile.Create('zxtyu');
end;
procedure FreeVars;
begin
IniFile.Free;
if Assigned(SCStrings) then
SCStrings.Free;
if Assigned(FBreakStrings) then
FBreakStrings.Free;
if Assigned(FBreakStrings) then
debugln('FBreakStrings is still assigned');
end;
InitVars and FreeVars run in the Execute procedure of the thread
When the loop runs again Assigned in InitVars is false so as soon as those
FBreakStrings and SCStrings are accessed within the loop a SIGSEGV occurs. So
what I want to know is whether Assigned remains true when Free is executed.
In the mean time instead of using Free in FreeVars I will set the text property
to the blank string to release the memory used by the strings.
--
Frank Church
=======================
http://devblog.brahmancreations.com
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http://lists.freepascal.org/mailman/listinfo/fpc-pascal
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