Hello List,

After googled and searching in the documentation,

http://free-pascal-general.1045716.n5.nabble.com/does-Advanced-Record-constructor-automatically-zero-all-the-memory-space-of-that-record-td5716755.html http://www.freepascal.org/docs-html/ref/refse23.html

i still have doubts about variable initialization:

1 - Does the compiler automatically initialize all class fields when a new instance is created?
2 - Does the compiler initialize record fields?
3 - When i declare a pointer as a global variable or as a member of a record, can i assume that its initial value is nil? 4 - Is there any compiler switch regarding initialization of variables?

Best regards

Mazola Winstrol wrote

1 - Does the compiler automatically initialize all class fields when a new instance is created?

They're called instance fields, and yes, they are zeroed. Class fields are fields that that are unique per class type, rather than per instance.

2 - Does the compiler initialize record fields?

Only for fields that are managed types.

3 - When i declare a pointer as a global variable or as a member of a record, can i assume that its initial value is nil?

No.

4 - Is there any compiler switch regarding initialization of variables?

There is only -gt, but it "initialises" (non-managed) variables and out-parameter with random data in order to more easily find cases of uninitialised data. It cannot be used to initialise all variables to a known value.

Jonas

2016-02-17 14:58 GMT-02:00 Jonas Maebe :

Thanks a lot for the explanation!

Regards

Jonas Maebe wrote

> 3 - When i declare a pointer as a global variable or as a member of a > record, can i assume that its initial value is nil? No.

Correction: all global variables are always zeroed, so that includes pointers, records and hence also pointers in records (if those records themselves are global variables). Pointers, records or record fields in are not zeroed because they are pointers/records/record fields though (so not in case they are local variables).

Jonas

2016-02-17 15:16 GMT-02:00 Jonas Maebe :

Just to clarify: if i have a record type with a pointer field, this field will always zeroed?

e.g

type
   TMyRecord = record
   private
     FMyPointer: Pointer;
   public
     property MyPointer: Pointer read FMyPointer;
   end;

......

procedure ShowMyPointerValue;
var
  MyRecord: TMyRecord;
begin
  writeln('My pointer value: ' + IntToStr(Integer(MyRecord.MyPointer)));
end;
end.

is correct to say that the above code will always print 'My pointer value: 0'?

Regards

Mazola Winstrol wrote

Just to clarify: if i have a record type with a pointer field, this field will always zeroed?

No. As mentioned, all global variables are always zeroed. The type doesn't matter. Local variables are never zeroed, except if they are managed types. A pointer is not a managed type.

Jonas

2016-02-18 18:38 GMT-02:00 Jonas Maebe :

May i add a remark about the behavior of managed types in the documentation?

http://www.freepascal.org/docs-html/current/ref/refse23.html#x55-730004.4

Regards

Jonas Maebe wrote

all global variables are always zeroed.

but it is better to not rely on it because

Local variables are never zeroed

and it is not uncommon that a part from main gets moved to a procedure, and all of a sudden you must add commands to initialize the variables. It is better to do it always, to avoid surprises.