A Debugger for Tcl Applications

Tcl is a language specifically intended for generic application control. By using it, application programmers escape the dilemma of whether to design sophisticated application-specific languages or whether to build tools more quickly but that are limited in flexibility. Tcl is easy for application programmers to use, however, up to now, there has been no general-purpose debugger for application users. This paper describes an implementation of a debugger for Tcl applications. The debugger has a typical front-end but with some extremely unusual commands, in part because of the features and limitations of Tcl. The debugger is modeless, allowing users to issue Tcl and application commands along with debugger commands. Each type of command may invoke the other, allowing debugging to be programmed, dynamically or in advance. The debugger is written in C and is very fast. When linked in but not used, it does not slow applications at all. The debugger requires no modifications to the Tcl core, and can be plugged into applications with little effort.