Operator: __DELETE

The operator is an extension of the IEC 61131-3 standard.

Important

For compatibility, the compiler version must be >= 3.3.2.0.

The operator releases the memory of instances that the "__NEW" operator generated dynamically. The __DELETE operator does not have a return value and the operand is set to zero after this operation.

Requirement: The Use dynamic memory allocation option is selected on the Application Build Options tab in the properties dialog of the application.

__DELETE (<pointer>)

Important

Two tasks should not call __DELETE simultaneously. Either you use a semaphore (SysSemEnter) or comparable method to prevent any concurrent calling of __DELETE , or you use __DELETE in one tasks only (recommended).

You can use a semaphore (SysSemEnter) to prevent two tasks from allocating memory at the same time. As a consequence, the extensive use of __DELETE causes higher jitter.

If Pointer references a function block, then CODESYS calls the associated FB_EXIT method before the pointer is set to zero.

Example 150. Example

Function Block

FUNCTION_BLOCK FBDynamic

VAR_INPUT
  in1, in2 : INT;
END_VAR

VAR_OUTPUT
  out : INT;
END_VAR

VAR
  test1 : INT := 1234;
  _inc : INT := 0;
  _dut : POINTER TO DUT;
  neu : BOOL;
END_VAR

out := in1 + in2;

Method (FB_Exit)

METHOD FB_Exit : BOOL

VAR_INPUT
  bInCopyCode : BOOL;
END_VAR

__Delete(_dut);

Method (FB_Init)

METHOD FB_Init : BOOL

VAR_INPUT
        bInitRetains : BOOL;
        bInCopyCode : BOOL;
END_VAR

_dut := __NEW(DUT);

Method

METHOD INC : INT

VAR_INPUT
END_VAR

_inc := _inc + 1;
INC := _inc;

Program

PLC_PRG(PRG)

VAR
        pFB : POINTER TO FBDynamic;
        bInit: BOOL := TRUE;
        bDelete: BOOL;
        loc : INT;
END_VAR

IF (bInit) THEN
        pFB := __NEW(FBDynamic);
        bInit := FALSE;
END_IF

IF (pFB <> 0) THEN
        pFB^(in1 := 1, in2 := loc, out => loc);
        pFB^.INC();
END_IF

IF (bDelete) THEN
        __DELETE(pFB);
END_IF