GDB: The GNU Debugger

2024-12-04 20:17:13 +0000

The GNU Debugger (GDB) is a portable debugger that runs on many Unix-like systems and works for many programming languages, including Ada, Assembly, C, C++, D, Fortran, Haskell, Go, Objective-C, OpenCL C, Modula-2, Pascal, Rust,[2] and partially others.

gdb ./bin/program

(gdb) set args foo bar

(gdb) b _start                  # breakpoint label
(gdb) b 20                      # breakpoint line number

(gdb) r                         # run
(gdb) c                         # continue
(gdb) s                         # step

(gdb) info registers            # show registers
(gdb) info f                    # show frame

Examining Memory

You can use the command x (for “examine”) to examine memory in any of several formats, independently of your program’s data types.

x/nfu addr
x addr
x

n, f, and u are all optional parameters that specify how much memory to display and how to format it; addr is an expression giving the address where you want to start displaying memory. If you use defaults for nfu, you need not type the slash ‘/’. Several commands set convenient defaults for addr.

n Repeat count The repeat count is a decimal integer; the default is 1.
f Display format The display format is one of the formats used by print.
u Unit size The unit size is any of b bytes h short w word g qword. 
(gdb) x 0x7fffffffdef0
0x7fffffffdef0:	0x0000000000000003

(gdb) x/8x 0x7fffffffdef0
0x7fffffffdef0:	0x0000000000000003 0x00007fffffffe24c
0x7fffffffdf00:	0x00007fffffffe284 0x00007fffffffe288
0x7fffffffdf10:	0x0000000000000000 0x00007fffffffe28c
0x7fffffffdf20:	0x00007fffffffe29c 0x00007fffffffe2f2

(gdb) x/1xb 0x7fffffffdef0
0x7fffffffdef0:	0x03