代码调试篇（1）：零基础快速掌握 gdb 常用命令
Author: stormQ
Created: Monday, 25. February 2019 10:31PM
Last Modified: Monday, 26. October 2020 10:30AM
本文描述了：1）启动调试进程的多种方式，从而提高调试效率；2）调试进程必须掌握的命令；3）如何使用 gdb 日志功能记录调试过程；4）其他常用命令。
命令：
# executable-file 为可执行文件的路径
$ gdb <executable-file>
示例：
# 启动一个不带参数的可执行程序 main，位于./samples目录下
$ gdb ./samples/main
命令：
# executable-file 为可执行文件的路径
# arg1 为可执行文件的第一个参数
# argn 为可执行文件的第n个参数
$ gdb --args <executable-file> <arg1> <argn>
示例：
# 启动一个带参数的可执行程序 main，位于./samples目录下
# 假设程序参数只有一个，为配置文件 ./config.txt
$ gdb --args ./samples/main ./config.txt
命令：
$ gdb
# process-id为要调试进程的进程ID
(gdb) attach <process-id>
示例：
$ gdb
# 假设要调试进程的进程ID为8888
(gdb) attach 8888
命令：
# command-file为存放gdb命令的文件
# 为了便于区分，该文件使用.gdb结尾（当然也可以使用其他格式结尾，比如：.txt）
$ gdb -x <command-file>
示例：
$ gdb -x main.gdb
假设 main.gdb 文件的内容为：
# 指定可执行文件的路径
file ./samples/main
# 设置可执行文件的参数（如果有的话）
set args ./config.txt
# 启动进程
start
# 继续执行
c
命令：
# info命名可缩写为i
(gdb) info proc
示例：
(gdb) i proc
process 11356
cmdline = '/home/tmp/b_Og'
cwd = '/home/tmp'
exe = '/home/tmp/b_Og'
从输出结果中可以看出，进程ID为 11356，进程启动项为 /home/tmp/b_Og，当前目录（即启动gdb时所在的目录）为 /home/tmp，可执行程序为 /home/tmp/b_Og。
命令：
(gdb) i threads
示例：
(gdb) i threads
Id Target Id Frame
* 1 Thread 0x7ffff7fce740 (LWP 1549) "main" 0x00007ffff7626c1d in nanosleep ()
at ../sysdeps/unix/syscall-template.S:84
2 Thread 0x7ffff6f42700 (LWP 1553) "main" 0x00007ffff7626c1d in nanosleep ()
at ../sysdeps/unix/syscall-template.S:84
打印结果中Id列左侧带*的为当前线程，ID列为 gdb 自定义的线程ID，Target Id为真实的线程ID（这里有两个线程，线程ID分别为：1549、1553），Frame为线程的当前帧（包含：线程运行到什么位置了等信息）。
命令：
(gdb) p $_thread
示例：
(gdb) p $_thread
$1 = 1
注意： 打印结果所显示的线程ID（这里是1）是 gdb 内部自定义的（即i threads命令输出结果中最左侧的Id列的值），而不是真实的线程ID。
命令：
# 只打印堆栈信息的调用层次
(gdb) bt
# 打印堆栈信息的调用层次，并打印函数参数和局部变量的值
(gdb) bt full
示例：
(gdb) bt
#0 0x00007ffff7626c1d in nanosleep () at ../sysdeps/unix/syscall-template.S:84
#1 0x0000000000401633 in std::this_thread::sleep_for<double, std::ratio<1l, 1000l> > (
__rtime=...) at /usr/include/c++/6/thread:323
#2 0x00000000004010ad in main () at main.cpp:11
(gdb) bt full
#0 0x00007ffff7626c1d in nanosleep () at ../sysdeps/unix/syscall-template.S:84
No locals.
#1 0x0000000000401633 in std::this_thread::sleep_for<double, std::ratio<1l, 1000l> > (
__rtime=...) at /usr/include/c++/6/thread:323
__s = {__r = 0}
__ns = {__r = 10000000}
__ts = {tv_sec = 0, tv_nsec = 7543688}
#2 0x00000000004010ad in main () at main.cpp:11
No locals.
命令：
# 只打印堆栈信息的调用层次
(gdb) thread apply all bt
或
# 只打印堆栈信息的调用层次
(gdb) thread apply all where
示例：
(gdb) thread apply all bt
Thread 2 (Thread 0x7ffff6f42700 (LWP 1553)):
#0 0x00007ffff7626c1d in nanosleep () at ../sysdeps/unix/syscall-template.S:84
#1 0x0000000000401633 in std::this_thread::sleep_for<double, std::ratio<1l, 1000l> > (
__rtime=...) at /usr/include/c++/6/thread:323
#2 0x00000000004019d7 in ShmManager::threadFunc (this=0x61fc20) at shm_manager_sim.cpp:49
#3 0x0000000000401841 in ShmManager::<lambda()>::operator()(void) const (
__closure=0x61fc68) at shm_manager_sim.cpp:28
#4 0x0000000000401e74 in std::_Bind_simple<ShmManager::start()::<lambda()>()>::_M_invoke<>(std::_Index_tuple<>) (this=0x61fc68) at /usr/include/c++/6/functional:1391
#5 0x0000000000401dfe in std::_Bind_simple<ShmManager::start()::<lambda()>()>::operator()(void) (this=0x61fc68) at /usr/include/c++/6/functional:1380
#6 0x0000000000401dce in std::thread::_State_impl<std::_Bind_simple<ShmManager::start()::<lambda()>()> >::_M_run(void) (this=0x61fc60) at /usr/include/c++/6/thread:197
#7 0x00007ffff7b0857f in ?? () from /usr/lib/x86_64-linux-gnu/libstdc++.so.6
#8 0x00007ffff761d6ba in start_thread (arg=0x7ffff6f42700) at pthread_create.c:333
#9 0x00007ffff735341d in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:109
Thread 1 (Thread 0x7ffff7fce740 (LWP 1549)):
#0 0x00007ffff7626c1d in nanosleep () at ../sysdeps/unix/syscall-template.S:84
#1 0x0000000000401633 in std::this_thread::sleep_for<double, std::ratio<1l, 1000l> > (
__rtime=...) at /usr/include/c++/6/thread:323
#2 0x00000000004010ad in main () at main.cpp:11
(gdb) thread apply all where
Thread 2 (Thread 0x7ffff6f42700 (LWP 1553)):
#0 0x00007ffff7626c1d in nanosleep () at ../sysdeps/unix/syscall-template.S:84
#1 0x0000000000401633 in std::this_thread::sleep_for<double, std::ratio<1l, 1000l> > (
__rtime=...) at /usr/include/c++/6/thread:323
#2 0x00000000004019d7 in ShmManager::threadFunc (this=0x61fc20) at shm_manager_sim.cpp:49
#3 0x0000000000401841 in ShmManager::<lambda()>::operator()(void) const (
__closure=0x61fc68) at shm_manager_sim.cpp:28
#4 0x0000000000401e74 in std::_Bind_simple<ShmManager::start()::<lambda()>()>::_M_invoke<>(std::_Index_tuple<>) (this=0x61fc68) at /usr/include/c++/6/functional:1391
#5 0x0000000000401dfe in std::_Bind_simple<ShmManager::start()::<lambda()>()>::operator()(void) (this=0x61fc68) at /usr/include/c++/6/functional:1380
#6 0x0000000000401dce in std::thread::_State_impl<std::_Bind_simple<ShmManager::start()::<lambda()>()> >::_M_run(void) (this=0x61fc60) at /usr/include/c++/6/thread:197
#7 0x00007ffff7b0857f in ?? () from /usr/lib/x86_64-linux-gnu/libstdc++.so.6
#8 0x00007ffff761d6ba in start_thread (arg=0x7ffff6f42700) at pthread_create.c:333
#9 0x00007ffff735341d in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:109
Thread 1 (Thread 0x7ffff7fce740 (LWP 1549)):
#0 0x00007ffff7626c1d in nanosleep () at ../sysdeps/unix/syscall-template.S:84
#1 0x0000000000401633 in std::this_thread::sleep_for<double, std::ratio<1l, 1000l> > (
__rtime=...) at /usr/include/c++/6/thread:323
#2 0x00000000004010ad in main () at main.cpp:11
命令：
# 先切换到指定线程，线程ID为gdb自定义的
(gdb) thread <thread-id-by-gdb>
# 只打印堆栈信息的调用层次
(gdb) bt
示例：
(gdb) thread 2
[Switching to thread 2 (Thread 0x7ffff6f42700 (LWP 1553))]
#0 0x00007ffff7626c1d in nanosleep () at ../sysdeps/unix/syscall-template.S:84
84 in ../sysdeps/unix/syscall-template.S
(gdb) bt
#0 0x00007ffff7626c1d in nanosleep () at ../sysdeps/unix/syscall-template.S:84
#1 0x0000000000401633 in std::this_thread::sleep_for<double, std::ratio<1l, 1000l> > (
__rtime=...) at /usr/include/c++/6/thread:323
#2 0x00000000004019d7 in ShmManager::threadFunc (this=0x61fc20) at shm_manager_sim.cpp:49
#3 0x0000000000401841 in ShmManager::<lambda()>::operator()(void) const (
__closure=0x61fc68) at shm_manager_sim.cpp:28
#4 0x0000000000401e74 in std::_Bind_simple<ShmManager::start()::<lambda()>()>::_M_invoke<>(std::_Index_tuple<>) (this=0x61fc68) at /usr/include/c++/6/functional:1391
#5 0x0000000000401dfe in std::_Bind_simple<ShmManager::start()::<lambda()>()>::operator()(void) (this=0x61fc68) at /usr/include/c++/6/functional:1380
#6 0x0000000000401dce in std::thread::_State_impl<std::_Bind_simple<ShmManager::start()::<lambda()>()> >::_M_run(void) (this=0x61fc60) at /usr/include/c++/6/thread:197
#7 0x00007ffff7b0857f in ?? () from /usr/lib/x86_64-linux-gnu/libstdc++.so.6
#8 0x00007ffff761d6ba in start_thread (arg=0x7ffff6f42700) at pthread_create.c:333
#9 0x00007ffff735341d in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:109
命令：
(gdb) show directories
示例：
(gdb) show directories
Source directories searched: $cdir:$cwd
命令：
# source-code-path 为要添加的源码搜索路径
(gdb) directory <source-code-path>
示例：
# 添加源码搜索路径为 /usr/include/boost/
(gdb) directory /usr/include/boost/
Source directories searched: /usr/include/boost:$cdir:$cwd
命令：
(gdb) directory
示例：
(gdb) directory
Reinitialize source path to empty? (y or n) y
Source directories searched: $cdir:$cwd
注意： 要查看源码，需要在编译时带-g选项。
命令：
(gdb) list <line-number>
示例：
(gdb) list 1
warning: Source file is more recent than executable.
1 #include "shm_manager_sim.h"
2 #include "topic_manager_sim.h"
3
4 int main()
5 {
6 TopicManager::instance();
7
8 ShmManager::instance()->start();
9
10 while(true)
命令：
(gdb) list <file-name>:<line-number>
示例：
(gdb) list shm_manager_sim.h:10
5 #include <thread>
6
7 class ShmManager;
8 typedef std::shared_ptr<ShmManager> ShmManagerPtr;
9
10 class ShmManager
11 {
12 public:
13 static const ShmManagerPtr& instance();
14 void start();
命令：
# 上翻源码
(gdb) list -
# 下翻源码
(gdb) list
示例：
(gdb) list shm_manager_sim.h:10
5 #include <thread>
6
7 class ShmManager;
8 typedef std::shared_ptr<ShmManager> ShmManagerPtr;
9
10 class ShmManager
11 {
12 public:
13 static const ShmManagerPtr& instance();
14 void start();
(gdb) list -
1 #ifndef ROS_SHM_MANAGER_H
2 #define ROS_SHM_MANAGER_H
3
4 #include <memory>
(gdb) list
5 #include <thread>
6
7 class ShmManager;
8 typedef std::shared_ptr<ShmManager> ShmManagerPtr;
9
10 class ShmManager
11 {
12 public:
13 static const ShmManagerPtr& instance();
14 void start();
命令：
# 只打印汇编代码
(gdb) disas <function-name>
# 打印汇编代码和对应的源码
(gdb) disas /m <function-name>
示例：
(gdb) disas main
Dump of assembler code for function main():
0x0000000000401046 <+0>: push %rbp
0x0000000000401047 <+1>: mov %rsp,%rbp
0x000000000040104a <+4>: sub $0x20,%rsp
0x000000000040104e <+8>: mov %fs:0x28,%rax
0x0000000000401057 <+17>: mov %rax,-0x8(%rbp)
0x000000000040105b <+21>: xor %eax,%eax
0x000000000040105d <+23>: callq 0x405248 <TopicManager::instance()>
0x0000000000401062 <+28>: callq 0x401776 <ShmManager::instance()>
0x0000000000401067 <+33>: mov %rax,%rdi
0x000000000040106a <+36>: callq 0x401172 <std::__shared_ptr<ShmManager, (__gnu_cxx::_Lock_policy)2>::operator->()
const>
0x000000000040106f <+41>: mov %rax,%rdi
0x0000000000401072 <+44>: callq 0x40184a <ShmManager::start()>
...
(gdb) disas /m main
Dump of assembler code for function main():
5 {
0x0000000000401046 <+0>: push %rbp
0x0000000000401047 <+1>: mov %rsp,%rbp
0x000000000040104a <+4>: sub $0x20,%rsp
0x000000000040104e <+8>: mov %fs:0x28,%rax
0x0000000000401057 <+17>: mov %rax,-0x8(%rbp)
0x000000000040105b <+21>: xor %eax,%eax
6 TopicManager::instance();
0x000000000040105d <+23>: callq 0x405248 <TopicManager::instance()>
7
8 ShmManager::instance()->start();
0x0000000000401062 <+28>: callq 0x401776 <ShmManager::instance()>
0x0000000000401067 <+33>: mov %rax,%rdi
0x000000000040106a <+36>: callq 0x401172 <std::__shared_ptr<ShmManager, (__gnu_cxx::_Lock_policy)2>::operator->() const>
0x000000000040106f <+41>: mov %rax,%rdi
0x0000000000401072 <+44>: callq 0x40184a <ShmManager::start()>
...
命令：
(gdb) b <file-name>:<line-number>
示例：
(gdb) b main.cpp:13
Breakpoint 2 at 0x40108c: file main.cpp, line 13.
命令：
(gdb) b <file-name>:<line-number> thread <thread-id-by-gdb>
示例：
(gdb) b main.cpp:13 thread 1
Breakpoint 5 at 0x40108c: file main.cpp, line 13.
命令：
(gdb) b *<address>
示例：
(gdb) b *0x00000000004010a1
Breakpoint 7 at 0x4010a1: file main.cpp, line 13.
命令：
(gdb) b <file-name>:<line-number> if <expresion>
示例：
(gdb) b main.cpp:14 if TopicManager::instance()->getNumSubscriptions() > 1000
Breakpoint 6 at 0x4010b2: file main.cpp, line 14.
(gdb) i breakpoints
Num Type Disp Enb Address What
5 breakpoint keep y 0x000000000040108c in main() at main.cpp:13 thread 1
stop only in thread 1
6 breakpoint keep y 0x00000000004010b2 in main() at main.cpp:14
stop only if TopicManager::instance()->getNumSubscriptions() > 1000
命令：
(gdb) i breakpoints
示例：
(gdb) i breakpoints
Num Type Disp Enb Address What
2 breakpoint keep y 0x000000000040108c in main() at main.cpp:13
3 breakpoint keep y 0x000000000040105d in main() at main.cpp:6
命令：
(gdb) i breakpoints <breakpoint-number>
示例：
(gdb) i breakpoints 2
Num Type Disp Enb Address What
2 breakpoint keep y 0x000000000040108c in main() at main.cpp:13
命令：
(gdb) i breakpoints <breakpoint-number>-<breakpoint-number>
示例：
(gdb) i breakpoints 2-3
Num Type Disp Enb Address What
2 breakpoint keep y 0x000000000040108c in main() at main.cpp:13
3 breakpoint keep y 0x000000000040105d in main() at main.cpp:6
命令：
(gdb) d
示例：
(gdb) d
Delete all breakpoints? (y or n) y
(gdb) i breakpoints
No breakpoints or watchpoints.
命令：
(gdb) d breakpoints <breakpoint-number>
示例：
(gdb) i breakpoints
Num Type Disp Enb Address What
4 breakpoint keep y 0x000000000040108c in main() at main.cpp:16
5 breakpoint keep y 0x000000000040105d in main() at main.cpp:8
(gdb) d breakpoints 4
(gdb) i breakpoints
Num Type Disp Enb Address What
5 breakpoint keep y 0x000000000040105d in main() at main.cpp:8
命令：
(gdb) d breakpoints <breakpoint-number>-<breakpoint-number>
示例：
(gdb) i breakpoints
Num Type Disp Enb Address What
5 breakpoint keep y 0x000000000040108c in main() at main.cpp:13 thread 1
stop only in thread 1
6 breakpoint keep y 0x00000000004010b2 in main() at main.cpp:14
stop only if TopicManager::instance()->getNumSubscriptions() > 1000
(gdb) d 5-6
(gdb) i breakpoints
No breakpoints or watchpoints.
命令：
# next命令可缩写为n
(gdb) next
示例：
(gdb) l
4 L_Subscription getAllSubscription();
5
6 TopicManagerPtr g_topic_manager;
7 std::mutex g_topic_manager_mutex;
8 const TopicManagerPtr& TopicManager::instance()
9 {
10 if (!g_topic_manager)
11 {
12 std::lock_guard<std::mutex> lock(g_topic_manager_mutex);
13 if (!g_topic_manager)
(gdb) n
10 if (!g_topic_manager)
(gdb) n
19 return g_topic_manager;
命令：
# nexti命令可缩写为ni
(gdb) nexti
示例：
(gdb) ni
0x0000000000405265 10 if (!g_topic_manager)
(gdb) ni
0x000000000040526a 10 if (!g_topic_manager)
命令：
# step命令可缩写为s
(gdb) step
示例：
(gdb) c
Continuing.
Thread 1 "main" hit Breakpoint 6, main () at main.cpp:14
14 if (TopicManager::instance()->getNumSubscriptions() > 1000)
(gdb) s
TopicManager::instance () at topic_manager_sim.cpp:9
9 {
(gdb) l
4 L_Subscription getAllSubscription();
5
6 TopicManagerPtr g_topic_manager;
7 std::mutex g_topic_manager_mutex;
8 const TopicManagerPtr& TopicManager::instance()
9 {
10 if (!g_topic_manager)
11 {
12 std::lock_guard<std::mutex> lock(g_topic_manager_mutex);
13 if (!g_topic_manager)
命令：
# stepi命令可缩写为si
(gdb) stepi
示例：
(gdb) si
TopicManager::instance () at topic_manager_sim.cpp:9
命令：
(gdb) finish
示例：
(gdb) s
TopicManager::instance () at topic_manager_sim.cpp:9
9 {
(gdb) finish
Run till exit from #0 TopicManager::instance () at topic_manager_sim.cpp:9
0x00000000004010b7 in main () at main.cpp:14
14 if (TopicManager::instance()->getNumSubscriptions() > 1000)
Value returned is $2 =
std::shared_ptr<TopicManager> (use count 1, weak count 0) = {get() = 0x620c30}
命令：
# continue命令可缩写为c
(gdb) continue
示例：
(gdb) c
Continuing.
Thread 1 "main" hit Breakpoint 6, main () at main.cpp:14
14 if (TopicManager::instance()->getNumSubscriptions() > 1000)
命令：
# print命令可缩写为p
(gdb) print <variable-name>
示例：
(gdb) p g_shm_manager
$3 = std::shared_ptr<ShmManager> (use count 1, weak count 0) = {get() = 0x620c80}
自动打印变量的值，命令：
(gdb) display <variable-name>
示例：
(gdb) display g_shm_manager
1: g_shm_manager = std::shared_ptr<ShmManager> (use count 1, weak count 0) = {get() = 0x620c80}
(gdb) n
13 std::this_thread::sleep_for(std::chrono::duration<double, std::milli>(10));
1: g_shm_manager = std::shared_ptr<ShmManager> (use count 1, weak count 0) = {get() = 0x620c80}
取消自动打印变量的值，命令：
(gdb) undisplay <display-number>
查看自动打印的变量有哪些，命令：
(gdb) i display
命令：
(gdb) p <variable-name>=<new-value>
示例：
(gdb) p g_shm_manager._M_ptr
$5 = (ShmManager *) 0x620c80
(gdb) p g_shm_manager._M_ptr=0
$6 = (ShmManager *) 0x0
命令：
(gdb) i args
命令：
(gdb) i locals
命令：
(gdb) i registers
示例：
(gdb) i registers
rax 0x0 0
rbx 0x0 0
rcx 0x7ffff7626c1d 140737343810589
rdx 0x0 0
rsi 0x7fffffffd8e0 140737488345312
rdi 0x0 0
rbp 0x7fffffffd930 0x7fffffffd930
rsp 0x7fffffffd910 0x7fffffffd910
r8 0x0 0
r9 0x7ffff6f42700 140737336583936
r10 0x1381 4993
r11 0x0 0
r12 0x400f50 4198224
r13 0x7fffffffda10 140737488345616
r14 0x0 0
r15 0x0 0
rip 0x4010b2 0x4010b2 <main()+108>
eflags 0x246 [ PF ZF IF ]
cs 0x33 51
ss 0x2b 43
ds 0x0 0
es 0x0 0
fs 0x0 0
gs 0x0 0
命令：
(gdb) i registers all
命令：
(gdb) p $<register-name>
示例：
(gdb) p $rcx
$9 = 140737343810589
命令：
(gdb) p $<register-name>=<new-value>
示例：
(gdb) p $rcx
$9 = 140737343810589
(gdb) p $rcx=1
$10 = 1
(gdb) p $rcx
$11 = 1
命令：
(gdb) x/<n><f><u> <address>
注：
n 表示要打印多少个单元（1个单元是指即参数u所指定的字节数），默认值为1。如果为正数，那么打印从地址addr后面的；否则打印从地址addr前面的。
f 表示输出格式，默认值为x（十六进制）。其他可选值：i，机器指令，忽略输出单元的大小；d，（有符号的）十进制；u，（无符号的）十进制；o，八进制；t，二进制；a，十六进制，省略最前面的0；s，字符串，且默认输出单元大小为b（bytes）。
u 表示输出单元大小，默认值为w（Words，4 bytes）。其他可选值：b，bytes；h，Halfwords，2 bytes；g，Giant words，8 bytes。注意：执行命令x时，如果没有显示指定输出单元大小，会默认使用上次所指定的值。
示例：
# 查看起始地址为0x7fb00008f0后面的4字节的内容，并以十六进制的格式输出
(gdb) x/wx 0x7fb00008f0
命令：
(gdb) call <function-name>
示例：
(gdb) call TopicManager::instance()->subscribe()
$13 = true
step 1： 查看是否开启 coredump
$ ulimit -c
注：如果输出结果为 0，那么未开启 coredump。
step 2： 开启 coredump
开启 coredump 并且不限制 core 文件大小（仅对当前会话有效）：
$ ulimit -c unlimited
step 3： 调试 coredump 文件
$ gdb <executable-file> <coredump-file-path>
注意： <executable-file>为发生 coredump 时所使用的可执行文件。
step 4： 查看堆栈信息
见本文的 查看堆栈信息
# 打开日志输出功能，且默认的日志输出文件名称为 gdb.txt
(gdb) set logging on
# 关闭日志输出功能
(gdb) set logging off
# 打开日志输出功能，并指定日志输出文件
# (gdb) set logging on gdb_log.txt
(gdb) set logging on <log-file>
注：打开日志输出功能后，gdb的输出会写入指定的日志文件。
(gdb) set logging file <log-file>
# 设置写日志文件的方式为：覆盖写
(gdb) set logging overwrite on
# 设置写日志文件的方式为：追加写
(gdb) set logging overwrite off
注：gdb 的默认方式为追加写。
注意： 设置覆盖写或追加写后，需要再次执行set logging on才会生效。
示例：
file ./main
set logging overwrite on
set logging on test.log
starrt
# gdb的输出只写入日志输出文件，不写入控制台
(gdb) set logging redirect on
# gdb的输出都会写入日志输出文件和控制台
(gdb) set logging redirect off
(gdb) show logging
Currently logging to "debug_navigator.txt".
Logs will be appended to the log file.
Output is being logged and displayed.
---Type to continue, or q to quit--- 的显示(gdb) set pagination off
…的完整内容(gdb) set print elements 0
(gdb) set listsize 30
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