如何计算可以用不同方法修改的属性？

Question

We have a class with a set of attributes and methods (that of course can call other class methods [not attribute methods]).

We need to create a tool that takes as an input the source code of the class and one method name and it should return the list of possibly modified class attributes by the code on the method chain. For example:

private int a;
private int b;
private int c;

public void M1()
{
    if (a == 2)
    {
        this.M3();
    }
}

public void M2()
{
    a = 3;
    this.M3();
}

public void M3()
{
    if (a == 7)
    {
        b = 1;
    }
    else
    {
        c = 2;
    }
}

In this case asking for M1 it should return b and c , asking for M2 it should return a , b and c and asking for M3 it should return b and c .

I have no idea on where to being with this as I never parsed code before ... thanks in advance.

EDIT: just to be clear, I don't need to evaluate the different paths, if I check M3 I'll always say that it affects b and c, I only care about possible changes, not the real ones.

Answer 1

I think your tool should run in a two fold manner, a first query to identify which variables are assigned to in each method and which methods are called in each method. The second query would take the method name, and trace the calls to the other methods, compiling which variables are assigned to, from each method subsequently traced to be called.

To detect an assignment to a variable (and I suggest simplifying the code in your parse, examining line-by-line and removing whitespace) look for an assignment operator ('=', but not '==', '*=', '+=' etc. and I think -> and others can assign as well, MSDN will tell you the full possibilities, try regular expressions if you know them), then you would need to identify the variable being assigned to, ie the variable name directly to the left of that operator (in most cases). Store a record of these variable assignments per method.

To detect a method call in code, you simply have to look for a method name within the method you are examining, then recursively look through that second method to find other methods and so forth... You could do the same as above to detect the method calls, then using a data structure of your own thinking, to loop through and find in that manner.

On top of that you have to worry about commented-out code, but if this is an early stages project, best not to worry yet :)