You can't debug what you can't see
Andrew Quinn, Jason Flinn, Michael Cafarella · 2019
The effectiveness of a debugging tool is fundamentally limited by what program state it can observe. Yet, for performance reasons, all current debugging tools restrict the program state that can be observed in some way. For example, tools like heap analysis restrict what can be observed (i.e., only global variables) and tools like core dump analysis restrict when observations may be made (i.e., only on program termination). Other tools effectively limit the scope of observation by requiring developers to specify what and when observations will be made before execution (e.g., logging) or during an execution (e.g., gdb).