Code Analysis: Fluid Call Tree

Let’s elaborate on the nature of these call tree diagrams.  Consider the following code:

void doStuff() 
{
     doOtherStuff(); 
}
void doOtherStuff() 
{
     init();
     final(); 
} 
void blah( int x ) 
{
     if ( x == 2 )
     {
         function();
         otherFunction();
     }
     else
     {
         doStuff();
     } 
}

Depending on the input for the blah function, we are going to experience two very different call graphs. If blah is called with a value of 2 for its input parameter x, then we would see a call tree like:

But on the other hand, if blah is called with any other value we end up with a call tree that looks like:

Any given program will potentially have a very large number of corresponding call trees.  A call forest if you will.  All things being equal, a small call forest is probably more comprehensible than a large one.  The idea here is that in order to really understand the program a software engineer will have to understand every call tree in a program’s call forest.  This is probably impractical in just about every real world program, so the software engineer will need to construct the program such that understanding a subset of the call trees will yield the necessary insight to effectively work with the program.

Next I want to talk about global variables, but first we need to look into abstract data types.