Techniques for tracing the real-time operation of software for the purposes of testing, debugging, or performance analysis are disclosed. Diagnostic instrumentation for generating records containing details of software operation is incorporated in the software by inserting calls to diverse macros or inline functions. Each macro takes an argument specifying both a subsystem and a category of instrumentation within the subsystem. Based on the specified subsystem and category, the instrumentation can be included or excluded from the compiled object code and, if included, can be dynamically enabled at run-time. Disabled instrumentation does not result in a function call, but only a single, inline "if," thereby reducing overhead. One macro accepts both software parameters and a custom format specifier describing how the parameters should be displayed. However, the parameters are not formatted during logging, nor is the format specifier included in the record. Instead, the formatting is performed when displayed.