This document provides an overview of debugging tools and techniques, focusing on the GNU Debugger (GDB). It discusses GDB basics like breakpoints, printing variables, and stepping through code. It also covers more advanced GDB features like visual mode, examining call frames, setting watchpoints, and reverse debugging. The document recommends using compiler flags for debugging, and introduces complementary tools like Valgrind and Clang sanitizers. It concludes that writing debuggable code through assertions and logging is the first step to troubleshooting bugs.

1. Debugging like a pro
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2. Motivation
- Debugging might be the
worst part of coding.
- Late night stress.
- Arm you with tools to
fight your run-times
bugs!

3. Scope
1. GDB basics.
2. GDB visual mode.
3. GDB frames.
4. GDB watchpoints.
5. GDB reverse walking.
6. GDB plugins & dotfiles.
7. Valgrind and clang sanitizer.
8. Your code.

4. GDB: Before invoking
GDB
Always use compiling flag for gdb:
$ g++ -g main.cpp
Invoke gdb in the following manner:
$ gdb [-tui] ./a.out

5. GDB: Basic commands
- gdb> r[un] : execute your code.
- gdb> b[reak] line|file:line|function : set a breakpoint.
- gdb> p[rint] variable : Display the variable name.
- gdb> n[ext] : Goes to next line.
- gdb> s[tep] : Goes inside the function currently in the PC.
- gdb> fin[ish] : Stop when we are returning.

6. GDB: Visual mode
- Always invoke GDB like : $ gdb -tui ./a.out
- Or in your standard GDB session press: C-x C-a
- Commands:
- gdb> focus src|cmd or C-x o
- Switch to single key mode C-x s

7. GDB: Visual
mode

8. GDB: Frames
- Whenever you enter a function you save the
context (frame) of the function.
- GDB allows you to go through all the frames
you have stacked:
- gdb> up
- gdb> down
- gdb> frame
- gdb> backtrace

9. GDB: Watchpoints
- Hardware vs. software watchpoints.
- Read, write, and read-write watchpoints (watch, rwatch, awatch)
- Easy to invoke:
- gdb> watch variable
- Also watch for conditions to happen.
- You need to be in the the same frame.
- Not a good feature for interframe code.

10. GDB: Reverse walking
- GDB let you go back in the time.
- It will record your code so it can go
backwards.
- Slow and resources expensive.

11. GDB: Reverse walking
- gdb> record [stop]
- gdb> reverse-continue [rc]
- gdb> reverse-step [rs]
- gdb> reverse-next [rn]
- gdb> set exec-direction forward|reverse

12. GDB: Plugins &
dotfiles
- You can customize and extend your gdb.
- Create your own perl or python functions.
to debug your data structures.
- Have a look to my dotfiles :)

13. Beyond GDB:
valgrind & clang
sanitizer
- Memory leaks are not
detectable with GDB.
- Valgrind will you out
with that, also you can
connect it to it.
- Even modern clang
versions performs
memory sanitization.

14. Your code the first debugger
When coding in C|C++ you have to great tools to prevent run-time bugs.
1. -DDEBUG macro. // Compile a debug version of your project.
2. assert(/* condition */) // Keep your pre-condition & variants.
Also, considering using logs, specially if your project is a Linux service (syslog).

15. Q&A