How do you debug a C program on Windows?

Question

I've never used a debugger and the time has come to give them a try. MinGW appears to come with GDB which I've been trying to use. Supposdly running gdb from the command line and typing run myprog.exe starts the debugger but when I do this I get

Starting program: C:\MinGW\bin\myprog.exe MyProg.exe [New Thread 1828.0xd8c] Error opening file. [Inferior 1 (process 1828) exited with code 02]

How to proceed or what's an easier way?

In particular I'm trying to flush out undefined behavior.

Answer 1

Since your program terminates, you'll need to set a breakpoint to see anything. Try break main before the run line. Then you can do commands line next (next line), step (step into/outof function calls), print expression (where expression can be a variable name or a function-call or a calculation), display expression (same as print, but prints just before each prompt). At any given point you can type backtrace to get a call stack. You can even type up and down to move up the callstack, so you can print higher local variables.

Answer 2

Well, the easiest way would be to use an IDE, actually. You might want to give code::blocks a try - very easy to use, configures everything for you on installation (just make sure to pick a compiler - don't worry, it'll prompt you) and there, you're all set and ready to go. As it's multi-platform, it doesn't really lock you into windows either, and gives you very powerful (and, I guess more importantly, convenient) possibilities of graphical debugging.

Answer 3

pass the binary with gdb

gdb <binary>

then set breakpoint to main

gdb) break main

Then run your program in gdb

gdb) run

then break point hits use 'n' or 'next' to step to different lines

gdb) n

Use 's' for stepping into function and 'p' printing var value

Example :

gdb) s <fun_name> 
gdb) p x