Where is the AccessViolation?

Development Programming & Scripting C++
1

Crash error:
Exception was “Access violation - code c0000005 (first/second chance not available)”

Last two lines of call stack:
UE4Editor_OrtCloud!AOrtCloudAIController::Tick() [f:\documents\unreal projects\ortcloud\source\ortcloud\ortcloudaicontroller.cpp:88]
UE4Editor_Engine!FActorTickFunction::ExecuteTick() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.9\engine\source\runtime\engine\private\actor.cpp:107]

Code Line in question:


86 .	if ( GetOrtPawn()->CoreSection && 
87 .	(GetOrtPawn()->OrderedTarget == NULL && GetOrtPawn()->OrderedDestination == GetOrtPawn()->CoreSection->GetActorLocation()) ||
88 .	((GetOrtPawn()->OrderedTarget && ODistance > 8500.0F) || GetOrtPawn()->OrderedDestination == GetOrtPawn()->CoreSection->GetActorLocation()) )

Call stack says its line 88.
GetOrtPawn() is a function that either returns an OrtPawn or NULL.
This entire block of code is wrapped in an if/then that checks if OrtPawn exists.
It seems to me, the only possible option on line 88 is GetOrtPawn()->CoreSection, which has been checked on line 86 and has to have PASSED in order to even get to line 88.

2

Uninitialized pointers will pass a null / nullptr condition. Have you initialized them as null or nullptr?

3

When you say “Uninitialized pointers will pass a null / nullptr condition” do you mean:

  1. Uninitialized pointers will be considered null/nullptr by the if check?
    or
  2. Uninitialized pointers will be considered passed(return true) by the if check?

EDIT:
CoreSection can indeed be uninitialized when the code runs this block.
So if you mean 2 that would explain why it is passing line 86 and crashing at subsequent parts of the if check.

4

Access violations are often caused by dereferencing corrupt pointers.

Corrupt pointers can be caused by invalid memory access

5

If you have a valid reference to a class which has a uninitialized pointer in it and you try to access it, it will give you an access validation. If you have a valid reference to a class and you have a condition for the uninitialized pointer in that class, it will evaluate as true, if it is follows:



if(GetOrtPawn()->CoreSection)
{
    // CoreSection can be uninitialized and still pass this condition.
}

You can solve this by setting CoreSection to NULL or nullptr in the constructor of your OrtPawn class.

**A broader example: **




class MyTestClass
{
public:
    MyTestClass() {}
    
    int ID;
};

class MyOtherTestClass
{
public:
	MyOtherTestClass(){}

    MyTestClass *ChildClass;
    
    float Area;
};

void TestingFunction()
{
    MyOtherTestClass *Testing = new MyOtherTestClass( );
    
    if(Testing)
    {
        if(Testing->ChildClass)
        {
            // Passes condition even though "TestingClass" is unitialized  
            printf("passes condition 
");
            
            // Crashes
            printf("%d", Testing->ChildClass->ID);
        }
    }
    
    delete Testing;
}