POU ‘CheckPointer’¶

Monitoring function for pointers (Checkpointer)

Use this function to monitor the memory access of pointers in runtime mode. As opposed to other monitoring functions, a standard suggestion does not exist for the implementation of CheckPointer. You must define an implementation according to your own requirements.

The CheckPointer function should check whether the returned pointer references a valid memory address; monitors whether the orientation of the referenced memory range matches the variable type that the pointer refers to. If both conditions are fulfilled, then the pointer is returned. If not, then the function should complete an appropriate error handling.

Caution

To obtain the feature for monitoring functions, do not edit the declaration section. However, you are permitted to add local variables.

Hint

An implicit monitoring function call does not occur for THIS pointer and SUPER pointer.

Hint

For complier version 3.5.7.40 and later, the implicit check function Checkpointer also acts on REFERENCE variables in the same way as on pointer variables.

Model

Declaration:

// Automatically generated code: DO NOT EDIT
FUNCTION CheckPointer : POINTER TO BYTE
VAR_INPUT
    ptToTest : POINTER TO BYTE;
    iSize : DINT;
    iGran : DINT;
    bWrite: BOOL;
END_VAR

Implementation: (incomplete)

// Not a standard implementation. Please add your own code here.
CheckPointer := ptToTest;

When the function is called, CODESYS provides the following input parameters:

ptToTest: Target address of the pointer
iSize: Size of the referenced variable; the data type of iSize must be compatible with INT and cover the dimensional scope of the variables.
iGran: Granularity of the referenced size; this is the largest non-structured data type contained in the referenced variables; the data type of iGran must be compatible with INT
bWrite: Access type (TRUE = write access, FALSE = read access); the data type of bWrite must be BOOL

When the result of the check is positive, the unchanged pointer is returned (ptToTest).