Cyclomatic Complexity Viewer

• Download VS.NET 2003 demo project - 108 Kb
• Download VS.NET 2003 source - 55.2 Kb
• Download VC++ 6 demo project - 43.5 Kb
• Download VC++ 6 source - 53.5 Kb

Introduction

The Cyclomatic Complexity Metric^[1] "measures the amount of decision logic in a single software module"^[2]. In my implementation I have taken the software module to be a function. The cyclomatic complexity "is based entirely on the structure of the software's control flow graph" ^[2]. The formula for calculating the cyclomatic complexity for each function using its control flow graph is:

where E and N are the number of edges and nodes in the control flow graph, respectively. Figure 1 displays the control flow graphs for the control structures found in the C++ language except for for. My understanding of the Cyclomatic Complexity Metric is that it measures how complex a function is and this determines how easy it will be to test the specific function.

if	if/else	while
do	switch

Figure 1. Control flow graphs

Background

At last after nearly five years of working on this add-in, I have finally released it. Why five years you may ask? Well after finding and implementing an algorithm to display directed graphs, improving the program, then discovering Graphviz, losing all the source code and starting from the beginning again, it has taken me that long. For the VC++ 6 version of the add-in, I have made use of Norm Almond's CLabel class. In the VS.NET 2003 version, I made use of Rashid Thadha's ATL version of the CLabel class.

Installing the Add-in

VS.NET 2003

After downloading the CCMetricViewer_DLL.zip file:

1. Extract the files using the folder names.
2. Double-click on the ReCreateCommands.reg file to register the add-in. After installation, the following buttons should appear on the toolbar: .
3. If nothing appears, click on the Tools menu item and select Add-in Manager... from the dropdown menu. The Add-in Manager dialog will appear. Now make sure that both the boxes for the Available Add-ins and the Startup are selected. The toolbar should appear now.
4. Also look at the View\Toolbars menu item and select Metric Viewer from the list.
5. If still nothing appears then try devenv.exe /setup.

VC++ 6

After downloading the VC6_DLL.zip file:

1. Extract the files using the folder names.
2. Click on the Tools menu item and select Customize... from the dropdown menu. The Customize dialog will appear. Click on the Add-ins and Macro Files tab. Click the checkbox labeled CycloComplexViewer Add-In to enable it.
3. The following button will appear:

   

Warning

This add-in is very buggy at the moment. It has a number of problems that still need to be fixed. Below is a list of the problems:

1. It cannot parse source code in the form of:

   if (A) D;

   or

   if (B) {C};

   However it will be able to parse source code in the form of:

   if (A)
      D;

   or

   if (B)
      {C}

2. The list display in the dialog does not automatically update when the scroll buttons are manipulated. It only updates itself once one scrolls down the list using the vertical scrollbars.

Using the Add-in

VS.NET 2003

Both buttons are used to calculate a cyclomatic complexity metric, however the matrices calculated are those of:

• A Specific Function
• All Functions of a Solution

respectively.

A Specific Function

The first button is used when you want to find out the cyclomatic complexity metric of a specific function. Just select the specific function and click the button. As shown in Figure 2(a) and 2(b), a dialog with the name of the function and its specific metric is displayed. If the metric value is greater than 10 the value is displayed in red, otherwise it is displayed in black.

Figure 2(a). Less than 10	Figure 2(b). Greater than 10

Figure 2. Metric for a specific selected function

All Functions of a Solution

The second button will calculate the cyclomatic complexity matrices of all the (global and member) functions found in the currently loaded Solution. Just click the button. As shown in Figure 3, a dialog with a list control containing all the functions in the Solution and their respective matrices is displayed.

Figure 3. All the matrices of the loaded Solution (Click here to enlarge)

In addition to the list, the dialog has a number of controls which can be used to manipulate the data.

Figure 4 shows the control that is used to set the metric level for comparisons. Initially it is set to the default value of 10. A number of people have recommended that a value of 10 is taken as the default level against which to compare cyclomatic complexity matrices of functions. Any function with a metric value higher than 10 is considered to be too complex and needs to be broken up into a number of smaller functions. The table below gives some idea:

1-10	-	a simple program
11-20	-	more complex
21-50	-	complex
> 50	-	untestable[3]

All functions with a metric value higher than the currently set metric level will be highlighted in the list. Figure 5 shows the results of applying the add-in to a currently loaded Solution and then setting the metric level to 5.

Figure 4. Default metric level of 10	Figure 5. Metric level set at 5 (Click here to enlarge)

Figure 6 shows the 'Export' button which can be used to have the results, as displayed in the list, exported to a pre-named XML file.

Figure 6. Export results to an XML file

The XML file has the following format:

<solution name="">
 <project name="">
  <class name="">
   <file name="">
   <function name="">
   <path name=""></path>
   <metric></metric>
   </function>
   </file>
  </class>
 </project>
 <project name="">
  ...
 </project>
 ...
</solution>

VC++ 6

The VC++ 6 version of the add-in can only determine the cyclomatic complexity metric for a single function. Select the function by highlighting the code for the specific function. Then click on the Add-in button and a dialog as in Figure 7 will appear displaying the metric value. If the metric value is greater than 10 the value is displayed in red, otherwise it is displayed in black.

Figure 7. Metric value of a specific selected function

Feedback

I will gladly appreciate any comments, suggestions, especially if it helps me fix the problems as stated in the Warning section.

References and Further Information

1. McCabe, T., "A Complexity Measure", IEEE Transactions on Software Engineering, December 1976.
2. Structured Testing: A Testing Methodology Using the Cyclomatic Complexity Metric
3. Cyclomatic Complexity

History

• 24 June 2005 - Added files for VC++ 6 version and updated article.
• 17 June 2005 - First public release.