gdb

Name: gdb
Author: mohitmishra786

460installs19forks

How to install gdb?

mohitmishra786/low-level-dev-skills/gdb

$npx -y skills add mohitmishra786/low-level-dev-skills --skill gdb

Installs into the current project.

Summary

GDB debugger skill for C/C++ programs. Use when starting a GDB session, setting breakpoints, stepping through code, inspecting variables, debugging crashes, using reverse debugging (record/replay), remote debugging with gdbserver, or loading core dumps. Activates on queries about

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SKILL.md

1	# GDB
2
3	## Purpose
4
5	Walk agents through GDB sessions from first launch to advanced workflows: crash diagnosis, reverse debugging, remote debugging, and multi-thread inspection.
6
7	## Triggers
8
9	- "My program segfaults / crashes — how do I debug it?"
10	- "How do I set a breakpoint on condition X?"
11	- "How do I inspect memory / variables in GDB?"
12	- "How do I debug a remote embedded target?"
13	- "GDB shows `??` frames / no source"
14	- "How do I replay a bug deterministically?" (record/replay)
15
16	## Workflow
17
18	### 1. Prerequisite: compile with debug info
19
20	Always compile with `-g` (GCC/Clang). Use `-Og` or `-O0` for most debuggable code.
21
22	```bash
23	gcc -g -Og -o prog main.c
24	```
25
26	For release builds: use `-g -O2` and keep the binary with symbols (strip separately with `objcopy`).
27
28	### 2. Start GDB
29
30	```bash
31	gdb ./prog # load binary
32	gdb ./prog core # load with core dump
33	gdb -p 12345 # attach to running process
34	gdb --args ./prog arg1 arg2 # pass arguments
35	gdb -batch -ex 'run' -ex 'bt' ./prog # non-interactive (CI)
36	```
37
38	### 3. Essential commands
39
40	\| Command \| Shortcut \| Effect \|
41	\|---------\|----------\|--------\|
42	\| `run [args]` \| `r` \| Start the program \|
43	\| `continue` \| `c` \| Resume after break \|
44	\| `next` \| `n` \| Step over (source line) \|
45	\| `step` \| `s` \| Step into \|
46	\| `nexti` \| `ni` \| Step over (instruction) \|
47	\| `stepi` \| `si` \| Step into (instruction) \|
48	\| `finish` \| \| Run to end of current function \|
49	\| `until N` \| \| Run to line N \|
50	\| `return [val]` \| \| Force return from function \|
51	\| `quit` \| `q` \| Exit GDB \|
52
53	### 4. Breakpoints and watchpoints
54
55	```gdb
56	break main # break at function
57	break file.c:42 # break at line
58	break *0x400abc # break at address
59	break foo if x > 10 # conditional break
60	tbreak foo # temporary breakpoint (fires once)
61	rbreak ^mylib_.* # regex breakpoint on all matching functions
62
63	watch x # watchpoint: break when x changes
64	watch (int)0x601060 # watch memory address
65	rwatch x # break when x is read
66	awatch x # break on read or write
67
68	info breakpoints # list all breakpoints
69	delete 3 # delete breakpoint 3
70	disable 3 # disable without deleting
71	enable 3
72	```
73
74	### 5. Inspect state
75
76	```gdb
77	print x # print variable
78	print/x x # print in hex
79	print *ptr # dereference pointer
80	print arr[0]@10 # print 10 elements of array
81	display x # auto-print x on every stop
82	undisplay 1
83
84	info locals # all local variables
85	info args # function arguments
86	info registers # all CPU registers
87	info registers rip rsp rbp # specific registers
88	x/10wx 0x7fff0000 # examine 10 words at address
89	x/s 0x400abc # examine as string
90	x/i $rip # examine current instruction
91
92	backtrace # call stack (bt)
93	bt full # bt + local vars
94	frame 2 # switch to frame 2
95	up / down # move up/down the stack
96	```
97
98	### 6. Multi-thread debugging
99
100	```gdb
101	info threads # list threads
102	thread 3 # switch to thread 3
103	thread apply all bt # backtrace all threads
104	thread apply all bt full # full bt all threads
105	set scheduler-locking on # pause other threads while stepping
106	```
107
108	### 7. Reverse debugging (record/replay)
109
110	Record requires `target record-full` or `target record-btrace` (Intel PT):
111
112	```gdb
113	# Software record (slow but universal)
114	record # start recording
115	run
116	# ... trigger the bug ...
117	reverse-continue # go back to last break
118	reverse-next # step backwards
119	reverse-step
120	reverse-finish
121
122	# Intel Processor Trace (fast, hardware)
123	target record-btrace pt
124	run
125	# view instruction history
126	record instruction-history
127	```
128
129	### 8. Remote debugging with gdbserver
130
131	On target:
132
133	```bash
134	gdbserver :1234 ./prog
135	# Or attach:
136	gdbserver :1234 --attach 5678
137	```
138
139	On host:
140
141	```bash
142	gdb ./prog
143	(gdb) target remote 192.168.1.10:1234
144	(gdb) break main
145	(gdb) continue
146	```
147
148	For cross-compilation: use `a

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gdb

460installs19forks

View on GitHub

How to install gdb?

mohitmishra786/low-level-dev-skills/gdb

$npx -y skills add mohitmishra786/low-level-dev-skills --skill gdb

Installs into the current project.

Summary

Files · 1

View on GitHub

SKILL.md

1	# GDB
2
3	## Purpose
4
5	Walk agents through GDB sessions from first launch to advanced workflows: crash diagnosis, reverse debugging, remote debugging, and multi-thread inspection.
6
7	## Triggers
8
9	- "My program segfaults / crashes — how do I debug it?"
10	- "How do I set a breakpoint on condition X?"
11	- "How do I inspect memory / variables in GDB?"
12	- "How do I debug a remote embedded target?"
13	- "GDB shows `??` frames / no source"
14	- "How do I replay a bug deterministically?" (record/replay)
15
16	## Workflow
17
18	### 1. Prerequisite: compile with debug info
19
20	Always compile with `-g` (GCC/Clang). Use `-Og` or `-O0` for most debuggable code.
21
22	```bash
23	gcc -g -Og -o prog main.c
24	```
25
26	For release builds: use `-g -O2` and keep the binary with symbols (strip separately with `objcopy`).
27
28	### 2. Start GDB
29
30	```bash
31	gdb ./prog # load binary
32	gdb ./prog core # load with core dump
33	gdb -p 12345 # attach to running process
34	gdb --args ./prog arg1 arg2 # pass arguments
35	gdb -batch -ex 'run' -ex 'bt' ./prog # non-interactive (CI)
36	```
37
38	### 3. Essential commands
39
40	\| Command \| Shortcut \| Effect \|
41	\|---------\|----------\|--------\|
42	\| `run [args]` \| `r` \| Start the program \|
43	\| `continue` \| `c` \| Resume after break \|
44	\| `next` \| `n` \| Step over (source line) \|
45	\| `step` \| `s` \| Step into \|
46	\| `nexti` \| `ni` \| Step over (instruction) \|
47	\| `stepi` \| `si` \| Step into (instruction) \|
48	\| `finish` \| \| Run to end of current function \|
49	\| `until N` \| \| Run to line N \|
50	\| `return [val]` \| \| Force return from function \|
51	\| `quit` \| `q` \| Exit GDB \|
52
53	### 4. Breakpoints and watchpoints
54
55	```gdb
56	break main # break at function
57	break file.c:42 # break at line
58	break *0x400abc # break at address
59	break foo if x > 10 # conditional break
60	tbreak foo # temporary breakpoint (fires once)
61	rbreak ^mylib_.* # regex breakpoint on all matching functions
62
63	watch x # watchpoint: break when x changes
64	watch (int)0x601060 # watch memory address
65	rwatch x # break when x is read
66	awatch x # break on read or write
67
68	info breakpoints # list all breakpoints
69	delete 3 # delete breakpoint 3
70	disable 3 # disable without deleting
71	enable 3
72	```
73
74	### 5. Inspect state
75
76	```gdb
77	print x # print variable
78	print/x x # print in hex
79	print *ptr # dereference pointer
80	print arr[0]@10 # print 10 elements of array
81	display x # auto-print x on every stop
82	undisplay 1
83
84	info locals # all local variables
85	info args # function arguments
86	info registers # all CPU registers
87	info registers rip rsp rbp # specific registers
88	x/10wx 0x7fff0000 # examine 10 words at address
89	x/s 0x400abc # examine as string
90	x/i $rip # examine current instruction
91
92	backtrace # call stack (bt)
93	bt full # bt + local vars
94	frame 2 # switch to frame 2
95	up / down # move up/down the stack
96	```
97
98	### 6. Multi-thread debugging
99
100	```gdb
101	info threads # list threads
102	thread 3 # switch to thread 3
103	thread apply all bt # backtrace all threads
104	thread apply all bt full # full bt all threads
105	set scheduler-locking on # pause other threads while stepping
106	```
107
108	### 7. Reverse debugging (record/replay)
109
110	Record requires `target record-full` or `target record-btrace` (Intel PT):
111
112	```gdb
113	# Software record (slow but universal)
114	record # start recording
115	run
116	# ... trigger the bug ...
117	reverse-continue # go back to last break
118	reverse-next # step backwards
119	reverse-step
120	reverse-finish
121
122	# Intel Processor Trace (fast, hardware)
123	target record-btrace pt
124	run
125	# view instruction history
126	record instruction-history
127	```
128
129	### 8. Remote debugging with gdbserver
130
131	On target:
132
133	```bash
134	gdbserver :1234 ./prog
135	# Or attach:
136	gdbserver :1234 --attach 5678
137	```
138
139	On host:
140
141	```bash
142	gdb ./prog
143	(gdb) target remote 192.168.1.10:1234
144	(gdb) break main
145	(gdb) continue
146	```
147
148	For cross-compilation: use `a

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