HotWire -- A Visual Debugger for C++

We argue that visualization is essential in a modern debugger. Instead of inserting debug statements throughout the code, it should be possible to easily define visualizations while running the program under control of the debugger, resulting in what might be called "visual printf's". A visualization of a C++ program can provide exciting insights. Bugs that cannot be found that easily with non-visual techniques are now found, just by watching the visualizations. However, the mechanisms to define the visualizations should be easy to understand, easy to apply and cause only minimal overhead to the programmer (who is the end-user of the visual debugger). HotWire is not only equipped with a couple of standard visualizations, but also with a small declarative script language (using constraints) that can be used to define new custom visualizations. This paper addresses user interface aspects of debugging tools. Specifically, the user interface of HotWire, a debugger for C++ and SmallTalk on AIX and OS/2 is described.