How to Use Breakpoints and Watch Expressions in Rust

Use cargo run -- --nocapture to run your program in a debugger, then set breakpoints and watch expressions in your IDE or GDB/LLDB.

cargo run -- --nocapture

In GDB:

(gdb) break main
(gdb) run
(gdb) watch my_variable
(gdb) continue

In VS Code (launch.json):

{
  "type": "lldb",
  "request": "launch",
  "name": "Debug",
  "cargo": {
    "args": ["run", "--", "--nocapture"]
  },
  "cwd": "${workspaceFolder}"
}

Set breakpoints by clicking the gutter in your editor. Add watch expressions in the debugger's watch panel (e.g., my_variable, vec.len()).

Breakpoints pause your code at a specific line so you can inspect it. Watch expressions let you track the value of a variable as your code runs. Think of it like pausing a movie to check the score on the screen.