What's your theory for why programmers reach for printf-debugging more frequently than other modes (like step-debugging)?

— Amjad Masad (@amasad) April 9, 2021

printf

• easier to show your changes
• can allow you to look back in time
• fast and reliable
• available everywhere
• printfs don’t disappear like breakpoints
• proactive
• smallest complexity cost
• (structured) logging mindset can help with understanding - e.g. messages with some story telling, gives better context
• made it here! - “hello world” sanity testing

debugger

• reverse debugging is rare
• examine program execution without making changes to the code
• tracepoints are quicker and easier than adding printfs, when they work
• can be a security nightmare in production
• requires setup
• shows more state than your printfs might have missed
• lots of rsi inducing button pushing
• can be non-trivial to attach a debugger
• better when you are unfamiliar with the code since multiple stack levels are shown
• some debuggers allow you to edit code whilst running which can help improve iteration speed
• some debuggers are fragile, breakpoints missed etc
• debuggers changes timing behaviour, so you may never hit a timing bug
• debuggers are like magic and you don’t know why it worked
• debuggers can be difficult in asynchronous environments