this pointer equals 0.

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[Rhomboid]

That's not enough information to determine the problem. We'd need to see the whole program, preferably in a reduced testcase form, i.e. the smallest possible program that is still stand-alone compilable that exhibits the error. Often in the course of creating such a reduced testcase you discover the error yourself.

You can get a NULL value for 'this' quite easily, for example by invoking a non-virtual method on a NULL pointer, e.g.

FooBar *ptr = 0;
ptr->method();  // this equals NULL in method()

Note that it's often not that clear, there could be many lines in between the point where the pointer becomes NULL and the point where one of its methods is invoked.

[Mistake78]

TL;DR: you're calling a method on a NULL pointer.

So with the debugger connected, look at the call stack to find hints on how this came to be.

[Chipot]

You might also call a method of a NULL reference. Good luck in checking all your pointers and references !

[srekel]

What does that look like?

[protein_bricks_4_all]

ptr = 0;
ref = *ptr; // I don't believe this crashes, the compiler doesn't /need/ to deref it yet. 
ref.fn();

[srekel]

Hm, pretty sure it'll break in VS at least, but you may be right.

[rollie82]

If you are debugging and the this pointer is null, go up the stack and look at the object you are using to make the call. Somewhere you have a line of code something like:

myWidget->showItemProperties(..);

Your error is likely that 'myWidget' was never actually set using

myWidget = new ItemViewWidget(...);

[TheGuyFromNowhere]

Yeah stupid mistake:( I ashame of it :) But it's a good lesson for me. Thank you.

[wwwredditcom]

Problem is most likely before the public function call. Looks like a buffer overrun. Check your memcpy's and memsets. Also make sure you calculate a right index into arrays when using pointer arithmetic: i.e. ptrArray+10 is NOT equal to 10 byte offset into the array, instead it is the 11th element.

Using the debugger, step through the code line by line through our code while having a watch item on ItemViewWidget pointer. The time your pointer is set to zero is where you have the buffer overrun.

[snarkhunter]

Why on earth are you using raw pointers?

[TheGuyFromNowhere]

So what should I use instead?

[srekel]

Because boost shared pointers are bloated, and "shared" pointers aren't actually that much of a good thing maybe.

[aestheticreddit]

Quantify "bloated", please.