Detecting Dead C++ Code

Oovaide has both static (compile-time) and dynamic (run-time) dead code detection.

Static Dead Code Detection

Oovaide uses CLang to parse C++ files. It finds all methods and functions, and determines with a call graph which functions are not called by another function. It outputs a table of the number of times each method or function is called. The table is viewable in a brower, and is also output as XML.

Typical output looks like the following:

    See the output directory for the text file output.
    The all usage count is the count of usage by all other methods. 
    
	Class Name Attribute Name Type All Use Count
	AddPackageDialog ~AddPackageDialog destr 0
	AddPackageDialog AddPackageDialog constr 0
	Editor DebugStatusChanged virt 0
	ModelData getBaseType 6

Class Name	Attribute Name	Type	All Use Count
AddPackageDialog	~AddPackageDialog	destr	0
AddPackageDialog	AddPackageDialog	constr	0
Editor	DebugStatusChanged	virt	0
ModelData	getBaseType		6

Some tool limitations are:

Implicit calls to constructors and destructors or assignment operators are shown as being unreferenced.
It is not possible to find out which virtual function is called, so they are displayed as being unreferenced
Multiple functions with the same name can exist in a project when they are used to build different components. Only one of them is used as the definition of the function, and the other called functions from the duplicately named functions will show up as being unreferenced. The tool can handle methods with the same name as long as they have unique signatures or are in different namespaces.

These issues only cause the problem that too many functions are listed as dead code, and therefore the tool is still useful for identifying true dead code.

Unused Members Detection

Members can be accessed within the class, from other classes or functions. They can also be accessed as a data member or to access a method of the data member. Typical output looks like the following:

    See the output directory for the text file output.
    The class usage count is the count of the number of methods in the same
    class that refer to the attribute. 
    
	Class Name Attribute Name Class Use Count All Use Count
	ComponentListItem mPathName 1 2
	PortionNode mNodeType 2 2

Class Name	Attribute Name	Class Use Count	All Use Count
ComponentListItem	mPathName	1	2
PortionNode	mNodeType	2	2

Some limitations are:

Classes with the same name used in different components within the project may list as having unused members.

The tool was run on the Oovaide project, and found many instances of dead code. This was a bit of a surprise since the project is written by a single author and the project has only about 40K lines of code.

Dynamic Dead Code Detection

Oovaide has a code coverage tool that is also built using CLang. It requires extensive tests written for the target project in order to be able to identify which code is not used. The description of the coverage tool is here. TestCoverage.html