How do you use gdb to debug your code?

Question

As a developer, how do you use gdb to track down bugs within your code? What techniques tricks do you use to make your life easier?

Answer 1

Some hints:

• use a graphical frontend (kdbg is quite good, ddd is at least better than command-line gdb, kdevelop has a nice gdb frontend but has some bgs, nemiver looks quite nice as well but is still in the works)
• make sure to have debug symbols and source code for all important parts (your own code and also some system libs)
  • on RedHat, you can install the -debuginfo packages to make both symbols and source code magically appear in the debugger - really cool because you can looks into libc function calls etc.
  • on Debian/Ubuntu, you can install the -dbg packages to get symbols; installing appropriate source files for system packages seems to be difficult, though
• I tend to add assert() and abort() calls in places that should not be reached, or in places that I want to study (some kind of heavy-weight breakpoint)
• ideally the assert() or abort() calls should be wrapped in some method or macro that only enables them in Debug releases, or even better that only enables them if a certain env var is set
• install a signal handler for SIGSEGV and SIGABRT; personally I check if a certain env var is set before installing the handlers; and in the handler I execute a hardcoded external command which usually lives somewhere in ~/.local/bin/; that command might then start kdbg and attach it to the crashing app. Voila, debugger pops up the moment your app does something bad.
• If you use unit tests, you could similarly attach a debugger whenever a test case fails, to inspect the app then.