---

12 Cross-Referencing Facility

The CMUCL cross-referencing facility (abbreviated XREF) assists in the analysis of static dependency relationships in a program. It provides introspection capabilities such as the ability to know which functions may call a given function, and the program contexts in which a particular global variable is used. The compiler populates a database of cross-reference information, which can be queried by the user to know:

• the list of program contexts (functions, macros, top-level forms) where a given function may be called at runtime, either directly or indirectly (via its function-object);
• the list of program contexts where a given global variable may be read;
• the list of program contexts that bind a global variable;
• the list of program contexts where a given global variable may be modified during the execution of the program.

A global variable is either a dynamic variable or a constant variable, for instance declared using defvar or defparameter or defconstant.

• Populating the cross-reference database
• Querying the cross-reference database
• Example usage
• Limitations of the cross-referencing facility