Pointers and fixed size buffers may only be used in an unsafe context

Scripting
1

Hey, so im having hard time adapting from C++ pointers to C# and i wonder why is this not compiling? Compiler: “Pointers and fixed size buffers may only be used in an unsafe context”.

struct ObstaclePixel
{
    public int x;
    public int y;
    public Color color;
    ObstaclePixel* next;
};

Thanks!:slight_smile:

2

What the heck are you doing that requires a pointer? Why won’t a normal reference work?

You can use pointers in C#. But it’s not reccomended at all. To do so you must write unsafe code.

3

Well basically im creating my own List. I need to keep track of both left and right values in an array and so this is a really fast way to do so. This way basically connects an array. Its pretty basic in dynamic programming tbh.

4

You can use C#'s LinkedList for this. (Doubley-Link list). ?
You could also create your own, without the need for pointers.

Node next, previous; // ya?
5

I understand the general structure. What I don’t understand is why a pointer instead of a reference?

6

I don’t have any good links for “C# for C++ programmers,” so here’s a brief run-down:

C# has things it calls “references” which work exactly like pointers except have limitations and auto-shortcuts. Anytime you declare a variable of a class type, it’s implicitly a pointer to that class, with implicit dereferencing. Ex: Cat c1 = new Cat(); c1.name=“fluffy”; is really Cat *c1; … c1->name=“fluffy”;. This means you can never create a class-type variable on the stack (since Cat c1; will always give a pointer.)

A funny rule is structs can’t be newed. When you use new myStruct(), it’s actually a fake new that does nothing. You’re just running the constructor. In C#, classes can only use pointers, and structs, ints, strings can never use pointers. Also for fun, you can’t use (*c1)=(*c2) to copy contents of the cats. There’s no star operation in C#, since it’s automatic whenever you try to use a field.

As you found, C# does have real pointers. But the point of using C# is the automatic garbage collection, which only works if you let it reference count, etc… by using “references.” Unsafe context is sort of a way to say it breaks garbage collection (and Unity also can run programs using it.)

For what you’re doing, just make ObstaclePixel be a class. Then ObstaclePixel next; is automatically a pointer to one. But, sure, C# also has something like the STL, with linkedList classes and so on.

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