Coca: an automated debugger for C

Abstract

Presents Coca, an automated debugger for C, where the breakpoint mechanism is based on events related to language constructs. Events have semantics, whereas the source lines used by most debuggers do not have any. A trace is a sequence of events. It can be seen as an ordered relation in a database. Users can specify precisely which events they want to see by specifying values for event attributes. At each event, visible variables can be queried. The trace query language is Prolog with a handful of primitives. The trace query mechanism searches through the execution traces using both control flow and data, whereas debuggers usually search according to either control flow or data. As opposed to fully "relational" debuggers which use plain database querying mechanisms, the Coca trace querying mechanism does not require any storage. The analysis is done on-the-fly, synchronously with the traced execution. Coca is therefore more powerful than "source-line" debuggers and more efficient than relational debuggers.