MSL2009. Gdb

Gdb Juan A. Suárez Romero Master on Free Software

List of topics ● Bugs ● Fixing bugs ● GDB ● Ways of working ● Coredumps ● Main basic commands Master on Free Software

What is a bug? ● Basically, an error in a program ● When a program performs as it shouldn't perform ● All software have bugs – Programming is complex – Human task -> errors Master on Free Software

Fixing bugs ● Have you ever debugged a program? ● Have you ever debugged a C program? ● A debugger allows you to check how a program is executed or checking what was doing when it crashed ● In gnome we use gdb for debugging Master on Free Software

GDB ● GNU Debugger ● Text mode – Other frontends: IDEs, emacs, DDD, XXGDB ● Trace the code – See what is doing – Inspect the data Master on Free Software

GDB ● Requirements to debug an application – Add debugging symbols -> not stripped – Remove optimizations (-O0) Master on Free Software

Ways of working ● debug a program, start and stop ● debug a running process ● debug a core file (cores activate) Master on Free Software

Core dumps ● Dump of information of a process when it crashes – See while it crashed – Inspect data ● ulimit -c <size of core> ● ./gdb <program> <core> Master on Free Software

Commands ● Run: runs the program from start ● Continue: continues running a stopped program ● Backtrace: show the stack ● Break: add a breakpoint ● Delete: delete a breakpoint ● Next: runs the current line to next ● Step: same as Next, but if current is a function, enter inside ● Print: print the content of a variable ● Display: same as Print, but more permanent Master on Free Software

Other commands ● Watchpoints (slow) ● Handle signals ● Remote debug ● Use the refcard: http://www.cs.dal.ca/studentservices/refcards/gdbref.pdf Master on Free Software

References ● refcard: www.cs.dal.ca/studentservices/refcards/gdbref.pdf ● http://www.gnu.org/software/gdb/gdb.html Master on Free Software

Acknowledgments ● Alejandro García Castro Master on Free Software

MSL2009. Gdb

by Juan A. Suárez Romero on Feb 11, 2010

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