GDB tutorial
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This document provides instructions for using the GDB debugger. It covers starting GDB and setting breakpoints, running and stepping through code, retrieving variable values, and debugging segmentation faults. Specifically: 1. It explains how to start GDB on an executable, set breakpoints, delete breakpoints, and run shell commands from within GDB. 2. It describes commands for running the program, listing code, stepping through code line-by-line or into functions, and continuing execution until the next breakpoint. 3. It details how to display, watch, and change the values of variables, call functions, and determine variable types. 4. It provides guidance on debugging segmentation faults by compiling with
GDB tutorial
- 1. GDB - Tutorial c Anurag (anurag@gnuer.org) March 9, 2006 1 Starting and invoking gdb 1. Inserting debugging information inside the output executable
- 2. les created after compilation and to start debugging session. $ gcc -o fact fact.c -g $ gdb fact 2. Giving shell commands from within gdb (gdb) shell clear 3. Set breakpoint at the function main() (gdb) break main 4. Delete break point number 1 (gdb) delete 1 Note: Pressing enter with no command executes the previous command 2 Running and navigating in gdb 1. Run program to be debugged (gdb) run 2. See where program stopped (gdb) list 3. Execute next line of the program (gdb) next (gdb) n 4. Step inside (gdb) step 1
- 3. 5. Print stack trace (gdb) where (gdb) frame 0 (gdb) frame 1 6. Return back from function (gdb) return 7. Continue execution until the next break point. (gdb) continue 3 Retrieving values of variables 1. Display the value of a variable "i" (gdb) display i 2. Set hardware/software watch point for variable "i" (gdb) watch i 3. Print the value of variable "i" (gdb) print i 4. Print the address of variable "i" (gdb) print &i 5. Reassign a value to n (gdb) set variable n=6 (gdb) continue 6. Call fact() function with dierent parameters. (gdb) call fact(4) 7. Display the data type of a variable: (gdb) ptype i (gdb) whatis i 4 Segmentation faults 1. Segmentation faults Here we compile and execute a program with results in a segmentation fault. The snapshot of memory is saved in a
- 4. le called core $ gcc -o demo demo.c -g 2
- 5. $ gdb demo core (gdb) disassembly note: sethi = an assembly instruction A Made with L TEX 3