A system and method for debugging a computer program by using a call graph. A call graph that represents trace events during execution of a debuggee program may be used as input to a system that enables a user to debug the debuggee program. Mechanisms facilitate conditionally forming clusters of event nodes, a cluster indicative of multiple event nodes corresponding to an execution of a source language statement. During a debugging session, in response to a command to perform a step operation, the nodes of a cluster are processed together so that a step corresponds to multiple events if the multiple events correspond to a single source language statement. A mechanism for inspecting variables is provided. Variable values may be selectively propagated and provided based on the call graph and a static control flow analysis of the debuggee program.