I'd love a tool that would observe my code during runtime - capturing all inputs and outputs from every function, as well as the value of each variable at each

I'd love a tool that would observe my code during runtime - capturing all inputs and outputs from every function, as well as the value of each variable at each point in the execution flow, and the call graph. Because this would probably incur a performance hit, I'd want to have the option to toggle it on/off. After execution, I can scroll through a tree of called functions and convert it into permanent "implementation documentation" (saved in a document I can annotate eg. with data flow, and edited when the code itself changes), helping me understand both the structure and dynamic control flow of code I'm learning or relearning after months of absence. I currently do this manually in Google Doc bullets, in order to make sense of legacy code whose control flow is fragmented into many function calls I must piece together mentally (as described in http://number-none.com/blow/john_carmack_on_inlined_code.html http://number-none.com/blow/john_carmack_on_inlined_code.htm...), and as a starting point for restructuring types and function graphs.