Using loops to solve the problem of recursive stack overflow

[erikzhang]

No description provided.

[erikzhang]

@shargon Can you take a look at this?

[shargon]

Why the equal method of Struct is different of Array, is needed?

[shargon]

I think that this doesn't solve this problem:

[Fact]
        public void OverFlow()
        {
            Struct s1 = new Struct { 1 };
            s1[0] = s1;

            Struct s2 = s1.Clone();
        }

[erikzhang]

In NeoVM, it is impossible that a struct contains itself. Because SETITEM and APPEND will clone the struct before setting the item.

[shargon]

Then why we need to change the clone method? when is the overflow produced?

[erikzhang]

If we limit the number of global StackItems, it will not overflow. However, if only the number of fields of the struct is limited, stack overflow will occur as long as there are too many nested layers.

[1, [2, [3, [...   //repeat 100000 times

[erikzhang]

Why the equal method of Struct is different of Array, is needed?

In many high level language, whether structs are equal depends on whether their fields are equal.

struct point
{
    int x;
    int y;
}

Take this struct as an example: (1, 2) is equal to another (1, 2).

[erikzhang]

@shargon Do you agree to merge this PR?