1.GDB调试基础
1. 不同级别符号表的区别
file cmd
wangguangbo@DESKTOP-O5D0MDL:/mnt/d/CMD$ g++ main.cpp -o cmd1 -g1
wangguangbo@DESKTOP-O5D0MDL:/mnt/d/CMD$ g++ main.cpp -o cmd2 -g2
wangguangbo@DESKTOP-O5D0MDL:/mnt/d/CMD$ g++ main.cpp -o cmd3 -g3
wangguangbo@DESKTOP-O5D0MDL:/mnt/d/CMD$ g++ main.cpp -o cmd
wangguangbo@DESKTOP-O5D0MDL:/mnt/d/CMD$ ll
-rwxrwxrwx 1 wangguangbo wangguangbo 16584 Mar 8 21:25 cmd*
-rwxrwxrwx 1 wangguangbo wangguangbo 16584 Mar 8 21:25 cmd1*
-rwxrwxrwx 1 wangguangbo wangguangbo 32624 Mar 8 21:25 cmd2*
-rwxrwxrwx 1 wangguangbo wangguangbo 115024 Mar 8 21:25 cmd3*
当可执行文件cmd没有调试信息时，空间最小
2. 使用file命令查看文件标识
wangguangbo@DESKTOP-O5D0MDL:/mnt/d/CMD$ file cmd
cmd: ELF 64-bit LSB pie executable, x86-64, version 1 (SYSV), dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, BuildID[sha1]=78bdc3e1b12130e4a4dd34030ce4b393e192de1a, for GNU/Linux 3.2.0, not stripped
wangguangbo@DESKTOP-O5D0MDL:/mnt/d/CMD$ file cmd1
cmd1: ELF 64-bit LSB pie executable, x86-64, version 1 (SYSV), dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, BuildID[sha1]=29da26c551768406ff057c1758b2fbece02599e2, for GNU/Linux 3.2.0, with debug_info, not stripped
wangguangbo@DESKTOP-O5D0MDL:/mnt/d/CMD$ file cmd2
cmd2: ELF 64-bit LSB pie executable, x86-64, version 1 (SYSV), dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, BuildID[sha1]=f5bceb7ff34b63351662b48666f5ed236ddbc13a, for GNU/Linux 3.2.0, with debug_info, not stripped
wangguangbo@DESKTOP-O5D0MDL:/mnt/d/CMD$ file cmd3
cmd3: ELF 64-bit LSB pie executable, x86-64, version 1 (SYSV), dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, BuildID[sha1]=8ac596bd15a4fd6995a2bf0b2822ca4ad01371a3, for GNU/Linux 3.2.0, with debug_info, not stripped
当输出包含debug_info 标识表示当前可执行文件包含调试信息
3. 查看可执行程序的程序段
3.1 cmd的程序段：
wangguangbo@DESKTOP-O5D0MDL:/mnt/d/CMD$ readelf -S cmd -W
There are 31 section headers, starting at offset 0x3908:
Section Headers:
[Nr] Name Type Address Off Size ES Flg Lk Inf Al
[ 0] NULL 0000000000000000 000000 000000 00 0 0 0
[ 1] .interp PROGBITS 0000000000000318 000318 00001c 00 A 0 0 1
[ 2] .note.gnu.property NOTE 0000000000000338 000338 000030 00 A 0 0 8
[ 3] .note.gnu.build-id NOTE 0000000000000368 000368 000024 00 A 0 0 4
[ 4] .note.ABI-tag NOTE 000000000000038c 00038c 000020 00 A 0 0 4
[ 5] .gnu.hash GNU_HASH 00000000000003b0 0003b0 000028 00 A 6 0 8
[ 6] .dynsym DYNSYM 00000000000003d8 0003d8 000138 18 A 7 1 8
[ 7] .dynstr STRTAB 0000000000000510 000510 000151 00 A 0 0 1
[ 8] .gnu.version VERSYM 0000000000000662 000662 00001a 02 A 6 0 2
[ 9] .gnu.version_r VERNEED 0000000000000680 000680 000070 00 A 7 2 8
[10] .rela.dyn RELA 00000000000006f0 0006f0 0000f0 18 A 6 0 8
[11] .rela.plt RELA 00000000000007e0 0007e0 000060 18 AI 6 24 8
[12] .init PROGBITS 0000000000001000 001000 00001b 00 AX 0 0 4
[13] .plt PROGBITS 0000000000001020 001020 000050 10 AX 0 0 16
[14] .plt.got PROGBITS 0000000000001070 001070 000010 10 AX 0 0 16
[15] .plt.sec PROGBITS 0000000000001080 001080 000040 10 AX 0 0 16
[16] .text PROGBITS 00000000000010c0 0010c0 0001ae 00 AX 0 0 16
[17] .fini PROGBITS 0000000000001270 001270 00000d 00 AX 0 0 4
[18] .rodata PROGBITS 0000000000002000 002000 000007 00 A 0 0 4
[19] .eh_frame_hdr PROGBITS 0000000000002008 002008 00003c 00 A 0 0 4
[20] .eh_frame PROGBITS 0000000000002048 002048 0000cc 00 A 0 0 8
[21] .init_array INIT_ARRAY 0000000000003d88 002d88 000008 08 WA 0 0 8
[22] .fini_array FINI_ARRAY 0000000000003d90 002d90 000008 08 WA 0 0 8
[23] .dynamic DYNAMIC 0000000000003d98 002d98 000200 10 WA 7 0 8
[24] .got PROGBITS 0000000000003f98 002f98 000068 08 WA 0 0 8
[25] .data PROGBITS 0000000000004000 003000 000010 00 WA 0 0 8
[26] .bss NOBITS 0000000000004040 003010 000118 00 WA 0 0 64
[27] .comment PROGBITS 0000000000000000 003010 00002b 01 MS 0 0 1
[28] .symtab SYMTAB 0000000000000000 003040 000450 18 29 21 8
[29] .strtab STRTAB 0000000000000000 003490 00035c 00 0 0 1
[30] .shstrtab STRTAB 0000000000000000 0037ec 00011a 00 0 0 1
Key to Flags:
W (write), A (alloc), X (execute), M (merge), S (strings), I (info),
L (link order), O (extra OS processing required), G (group), T (TLS),
C (compressed), x (unknown), o (OS specific), E (exclude),
D (mbind), l (large), p (processor specific)
3.2 cmd1的程序段：
wangguangbo@DESKTOP-O5D0MDL:/mnt/d/CMD$ readelf -S cmd1 -W
There are 37 section headers, starting at offset 0x3c90:
Section Headers:
[Nr] Name Type Address Off Size ES Flg Lk Inf Al
[ 0] NULL 0000000000000000 000000 000000 00 0 0 0
[ 1] .interp PROGBITS 0000000000000318 000318 00001c 00 A 0 0 1
[ 2] .note.gnu.property NOTE 0000000000000338 000338 000030 00 A 0 0 8
[ 3] .note.gnu.build-id NOTE 0000000000000368 000368 000024 00 A 0 0 4
[ 4] .note.ABI-tag NOTE 000000000000038c 00038c 000020 00 A 0 0 4
[ 5] .gnu.hash GNU_HASH 00000000000003b0 0003b0 000028 00 A 6 0 8
[ 6] .dynsym DYNSYM 00000000000003d8 0003d8 000138 18 A 7 1 8
[ 7] .dynstr STRTAB 0000000000000510 000510 000151 00 A 0 0 1
[ 8] .gnu.version VERSYM 0000000000000662 000662 00001a 02 A 6 0 2
[ 9] .gnu.version_r VERNEED 0000000000000680 000680 000070 00 A 7 2 8
[10] .rela.dyn RELA 00000000000006f0 0006f0 0000f0 18 A 6 0 8
[11] .rela.plt RELA 00000000000007e0 0007e0 000060 18 AI 6 24 8
[12] .init PROGBITS 0000000000001000 001000 00001b 00 AX 0 0 4
[13] .plt PROGBITS 0000000000001020 001020 000050 10 AX 0 0 16
[14] .plt.got PROGBITS 0000000000001070 001070 000010 10 AX 0 0 16
[15] .plt.sec PROGBITS 0000000000001080 001080 000040 10 AX 0 0 16
[16] .text PROGBITS 00000000000010c0 0010c0 0001ae 00 AX 0 0 16
[17] .fini PROGBITS 0000000000001270 001270 00000d 00 AX 0 0 4
[18] .rodata PROGBITS 0000000000002000 002000 000007 00 A 0 0 4
[19] .eh_frame_hdr PROGBITS 0000000000002008 002008 00003c 00 A 0 0 4
[20] .eh_frame PROGBITS 0000000000002048 002048 0000cc 00 A 0 0 8
[21] .init_array INIT_ARRAY 0000000000003d88 002d88 000008 08 WA 0 0 8
[22] .fini_array FINI_ARRAY 0000000000003d90 002d90 000008 08 WA 0 0 8
[23] .dynamic DYNAMIC 0000000000003d98 002d98 000200 10 WA 7 0 8
[24] .got PROGBITS 0000000000003f98 002f98 000068 08 WA 0 0 8
[25] .data PROGBITS 0000000000004000 003000 000010 00 WA 0 0 8
[26] .bss NOBITS 0000000000004040 003010 000118 00 WA 0 0 64
[27] .comment PROGBITS 0000000000000000 003010 00002b 01 MS 0 0 1
[28] .debug_aranges PROGBITS 0000000000000000 00303b 000030 00 0 0 1
[29] .debug_info PROGBITS 0000000000000000 00306b 000097 00 0 0 1
[30] .debug_abbrev PROGBITS 0000000000000000 003102 00007a 00 0 0 1
[31] .debug_line PROGBITS 0000000000000000 00317c 00008b 00 0 0 1
[32] .debug_str PROGBITS 0000000000000000 003207 00013a 01 MS 0 0 1
[33] .debug_line_str PROGBITS 0000000000000000 003341 000031 01 MS 0 0 1
[34] .symtab SYMTAB 0000000000000000 003378 000450 18 35 21 8
[35] .strtab STRTAB 0000000000000000 0037c8 00035c 00 0 0 1
[36] .shstrtab STRTAB 0000000000000000 003b24 00016a 00 0 0 1
Key to Flags:
W (write), A (alloc), X (execute), M (merge), S (strings), I (info),
L (link order), O (extra OS processing required), G (group), T (TLS),
C (compressed), x (unknown), o (OS specific), E (exclude),
D (mbind), l (large), p (processor specific)
可见使用 -gX 编译选项的可执行文件 .debug 的调试段
3.2 cmd2的程序段
wangguangbo@DESKTOP-O5D0MDL:/mnt/d/CMD$ readelf -S cmd2 -W
There are 37 section headers, starting at offset 0x7630:
Section Headers:
[Nr] Name Type Address Off Size ES Flg Lk Inf Al
[ 0] NULL 0000000000000000 000000 000000 00 0 0 0
[ 1] .interp PROGBITS 0000000000000318 000318 00001c 00 A 0 0 1
[ 2] .note.gnu.property NOTE 0000000000000338 000338 000030 00 A 0 0 8
[ 3] .note.gnu.build-id NOTE 0000000000000368 000368 000024 00 A 0 0 4
[ 4] .note.ABI-tag NOTE 000000000000038c 00038c 000020 00 A 0 0 4
[ 5] .gnu.hash GNU_HASH 00000000000003b0 0003b0 000028 00 A 6 0 8
[ 6] .dynsym DYNSYM 00000000000003d8 0003d8 000138 18 A 7 1 8
[ 7] .dynstr STRTAB 0000000000000510 000510 000151 00 A 0 0 1
[ 8] .gnu.version VERSYM 0000000000000662 000662 00001a 02 A 6 0 2
[ 9] .gnu.version_r VERNEED 0000000000000680 000680 000070 00 A 7 2 8
[10] .rela.dyn RELA 00000000000006f0 0006f0 0000f0 18 A 6 0 8
[11] .rela.plt RELA 00000000000007e0 0007e0 000060 18 AI 6 24 8
[12] .init PROGBITS 0000000000001000 001000 00001b 00 AX 0 0 4
[13] .plt PROGBITS 0000000000001020 001020 000050 10 AX 0 0 16
[14] .plt.got PROGBITS 0000000000001070 001070 000010 10 AX 0 0 16
[15] .plt.sec PROGBITS 0000000000001080 001080 000040 10 AX 0 0 16
[16] .text PROGBITS 00000000000010c0 0010c0 0001ae 00 AX 0 0 16
[17] .fini PROGBITS 0000000000001270 001270 00000d 00 AX 0 0 4
[18] .rodata PROGBITS 0000000000002000 002000 000007 00 A 0 0 4
[19] .eh_frame_hdr PROGBITS 0000000000002008 002008 00003c 00 A 0 0 4
[20] .eh_frame PROGBITS 0000000000002048 002048 0000cc 00 A 0 0 8
[21] .init_array INIT_ARRAY 0000000000003d88 002d88 000008 08 WA 0 0 8
[22] .fini_array FINI_ARRAY 0000000000003d90 002d90 000008 08 WA 0 0 8
[23] .dynamic DYNAMIC 0000000000003d98 002d98 000200 10 WA 7 0 8
[24] .got PROGBITS 0000000000003f98 002f98 000068 08 WA 0 0 8
[25] .data PROGBITS 0000000000004000 003000 000010 00 WA 0 0 8
[26] .bss NOBITS 0000000000004040 003010 000118 00 WA 0 0 64
[27] .comment PROGBITS 0000000000000000 003010 00002b 01 MS 0 0 1
[28] .debug_aranges PROGBITS 0000000000000000 00303b 000030 00 0 0 1
[29] .debug_info PROGBITS 0000000000000000 00306b 0022d2 00 0 0 1
[30] .debug_abbrev PROGBITS 0000000000000000 00533d 000596 00 0 0 1
[31] .debug_line PROGBITS 0000000000000000 0058d3 000156 00 0 0 1
[32] .debug_str PROGBITS 0000000000000000 005a29 00108d 01 MS 0 0 1
[33] .debug_line_str PROGBITS 0000000000000000 006ab6 000262 01 MS 0 0 1
[34] .symtab SYMTAB 0000000000000000 006d18 000450 18 35 21 8
[35] .strtab STRTAB 0000000000000000 007168 00035c 00 0 0 1
[36] .shstrtab STRTAB 0000000000000000 0074c4 00016a 00 0 0 1
Key to Flags:
W (write), A (alloc), X (execute), M (merge), S (strings), I (info),
L (link order), O (extra OS processing required), G (group), T (TLS),
C (compressed), x (unknown), o (OS specific), E (exclude),
D (mbind), l (large), p (processor specific
比较得出包含的debug段占用空间更大
4.编译选项总结
| 选项 | 调试信息详细程度 | 二进制文件大小 | 包含的关键信息 |
|---|---|---|---|
| -g1 | 最低级别 | 最小 | 基本行号、函数名、变量类型信息 |
| -g2 | 默认级别(如直接使用-g) | 中等 | 完整行号、函数、变量、结构体布局 |
| -g3 | 最高级别 | 最大 | 额外包含宏定义、内联函数、模板实例化信息 |
5.使用GDB调试
5.1 不包含符号表的GDB启动信息
wangguangbo@DESKTOP-O5D0MDL:/mnt/d/CMD$ gdb ./cmd
GNU gdb (Ubuntu 15.0.50.20240403-0ubuntu1) 15.0.50.20240403-git
Copyright (C) 2024 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
Type "show copying" and "show warranty" for details.
This GDB was configured as "x86_64-linux-gnu".
Type "show configuration" for configuration details.
For bug reporting instructions, please see:
<https://www.gnu.org/software/gdb/bugs/>.
Find the GDB manual and other documentation resources online at:
<http://www.gnu.org/software/gdb/documentation/>.
For help, type "help".
Type "apropos word" to search for commands related to "word"...
Reading symbols from ./cmd...
This GDB supports auto-downloading debuginfo from the following URLs:
<https://debuginfod.ubuntu.com>
Enable debuginfod for this session? (y or [n]) n
Debuginfod has been disabled.
To make this setting permanent, add 'set debuginfod enabled off' to .gdbinit.
(No debugging symbols found in ./cmd)
5.2 包含符号表的GDB启动信息
wangguangbo@DESKTOP-O5D0MDL:/mnt/d/CMD$ gdb ./cmd1
GNU gdb (Ubuntu 15.0.50.20240403-0ubuntu1) 15.0.50.20240403-git
Copyright (C) 2024 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
Type "show copying" and "show warranty" for details.
This GDB was configured as "x86_64-linux-gnu".
Type "show configuration" for configuration details.
For bug reporting instructions, please see:
<https://www.gnu.org/software/gdb/bugs/>.
Find the GDB manual and other documentation resources online at:
<http://www.gnu.org/software/gdb/documentation/>.
For help, type "help".
Type "apropos word" to search for commands related to "word"...
Reading symbols from ./cmd1...
(gdb) q
**注意 ** ： GDB对于符号表的提示不同
局部变量的区别
gdb ./cmd1
(gdb) b main
Breakpoint 1 at 0x11e4: file main.cpp, line 91.
(gdb) r
Starting program: /mnt/d/CMD/cmd1
Breakpoint 1, main () at main.cpp:91
91 int main() {
(gdb) i locals
No locals.
(gdb) q
wangguangbo@DESKTOP-O5D0MDL:/mnt/d/CMD$ gdb -q ./cmd2
Reading symbols from ./cmd2...
(gdb) b main
Breakpoint 1 at 0x11e4: file main.cpp, line 91.
(gdb) r
Starting program: /mnt/d/CMD/cmd2
This GDB supports auto-downloading debuginfo from the following URLs:
<https://debuginfod.ubuntu.com>
Enable debuginfod for this session? (y or [n]) n
Debuginfod has been disabled.
To make this setting permanent, add 'set debuginfod enabled off' to .gdbinit.
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
Breakpoint 1, main () at main.cpp:91
91 int main() {
(gdb) r
The program being debugged has been started already.
Start it from the beginning? (y or n) y
Starting program: /mnt/d/CMD/cmd2
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
Breakpoint 1, main () at main.cpp:91
91 int main() {
(gdb) i locals
a = {-8704, 32767, -137661553, 32767, -135812528}
p = 0x6c6f6f705f68652e
区别 ： -g2 可以通过 i locals 命令查看到变量信息
5.3 包含符号表的GDB启动信息
-g1 编译选项下的输出
wangguangbo@DESKTOP-O5D0MDL:/mnt/d/CMD$ gdb -q ./cmd1
Reading symbols from ./cmd1...
(gdb) b main
Breakpoint 1 at 0x11e4: file main.cpp, line 91.
(gdb) r
Starting program: /mnt/d/CMD/cmd1
This GDB supports auto-downloading debuginfo from the following URLs:
<https://debuginfod.ubuntu.com>
Enable debuginfod for this session? (y or [n]) n
Debuginfod has been disabled.
To make this setting permanent, add 'set debuginfod enabled off' to .gdbinit.
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
Breakpoint 1, main () at main.cpp:91
warning: Source file is more recent than executable.
(gdb) macro expand MAX
expands to: MAX
(gdb)
-g2 编译选项下的输出
wangguangbo@DESKTOP-O5D0MDL:/mnt/d/CMD$ gdb -q ./cmd2
Reading symbols from ./cmd2...
(gdb) b main
Breakpoint 1 at 0x11e4: file main.cpp, line 91.
(gdb) r
Starting program: /mnt/d/CMD/cmd2
This GDB supports auto-downloading debuginfo from the following URLs:
<https://debuginfod.ubuntu.com>
Enable debuginfod for this session? (y or [n]) n
Debuginfod has been disabled.
To make this setting permanent, add 'set debuginfod enabled off' to .gdbinit.
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
Breakpoint 1, main () at main.cpp:91
warning: Source file is more recent than executable.
(gdb) i loacals
Undefined info command: "loacals". Try "help info".
(gdb) i locals
a = {-8704, 32767, -137661553, 32767, -135812528}
p = 0x6c6f6f705f68652e
(gdb) info macro MAX
Defined at <user-defined>:-1
#define MAX
-g3 编译选项下的输出
wangguangbo@DESKTOP-O5D0MDL:/mnt/d/CMD$ gdb -q ./cmd3
Reading symbols from ./cmd3...
(gdb) b main
Breakpoint 1 at 0x24a4: file main.cpp, line 33.
(gdb) r
Starting program: /mnt/d/CMD/cmd3
This GDB supports auto-downloading debuginfo from the following URLs:
<https://debuginfod.ubuntu.com>
Enable debuginfod for this session? (y or [n]) n
Debuginfod has been disabled.
To make this setting permanent, add 'set debuginfod enabled off' to .gdbinit.
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
Breakpoint 1, main (argc=1, argv=0x7fffffffdea8) at main.cpp:33
33 int main(int argc, char *argv[]) {
(gdb) i locals
a = 0
buf = "\270\336\377\377\377\177\000\000\000+\243-{c\363W \335\377\377\377\177\000\000\300:\240\367\377\177\000\000\377\021
\000\000\000\000\000\000\230\377\377\377\377\377\377\377\270\336\377\377\377\177\000\000\230\303\346\367\377\177\000\000`\
335\377\377\377\177\000\000\022؊\367\377\177\000\000`\335\377\377\377\177\000\000@\303\346\367\377\177\000\000glibcxx.\000 \001\000\000\000\000\000glibcxx..eh_pool"
str = ""
f = {<No data fields>}
(gdb) l
28 printf("cnt: %d\n", cnt);
29 return -2;
30 }
31
32
33 int main(int argc, char *argv[]) {
34 int a = 123;
35 char buf[128] = "456";
36 std::string str = "abc";
37
(gdb) macro expand MAX
expands to: (9988)
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