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SA0039: Possible null-pointer deferences

Detects code locations where a null pointer is possibly dereferenced

Justification: A pointer should be checked before each dereferencing to make sure it is not equal to zero. Otherwise an access violation may occur at runtime.

Importance: High

Example 114. Example
PROGRAM PLC_PRG
VAR
    ptiVar1:POINTER TO INT;
    ptiVar2:POINTER TO INT;
    ptiVar3:POINTER TO INT;
    iVar:INT;
    iCount :INT;
    iCondition: INT;
END_VAR

iCount := iCount + INT#1;
ptiVar1 := ADR(iVar);
ptiVar1^ := iCondition;    // OK - valid reference
ptiVar2^ := iCondition;    // SA0039 - null pointer dereferenciation
iVar := ptiVar3^;    // SA0039 - null pointer dereferenciation

Output in the Messages view:

  • sa_icon_message.png SA0039: Possible null-pointer deference 'ptiVar2^'

  • sa_icon_message.png SA0039: Possible null-pointer deference 'ptiVar3^'



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