1 #include<stdio.h>
2
3 int Sum(int s,int e)
4 {
5 int result = 0;
6 int i = s;
7 for(;i <= e;i++)
8 {
9 result += i;
10 }
11
12 return result;
13 }
14
15 int main()
16 {
17 int start = 1;
18 int end = 100;
19 printf("I will begin\n");
20 int n = Sum(start,end);
21 printf("running done,result is：[%d-%d]=%d\n",start,end,n);
22
23 return 0;
24 }
7.1.2 代码运行
bash复制代码
[Alice@VM-4-17-centos mycmd]$ vim Makefile
[Alice@VM-4-17-centos mycmd]$ make
gcc -o cmd.exe mycmd.c
[Alice@VM-4-17-centos mycmd]$ ./cmd.exe
I will begin
running done,result is：[1-100]=5050
[Alice@VM-4-17-centos mycmd]$ gdb cmd.exe
GNU gdb (GDB) Red Hat Enterprise Linux 7.6.1-120.el7
Copyright (C) 2013 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-redhat-linux-gnu".
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>...
Reading symbols from /home/Alice/118/linux-git/mycmd/cmd.exe...(no debugging symbols found)...done.
(gdb) quit
$ gcc mycmd.c -o mycmd # 默认模式，不⽀持调试
$ file mycmd
mycmd: ELF 64-bit LSB shared object, x86-64, version 1 (SYSV), dynamically
linked, interpreter /lib64/ld-linux-x86-64.so.2,
BuildID[sha1]=82f5cbaada10a9987d9f325384861a88d278b160, for GNU/Linux
3.2.0, not stripped
$ gcc mycmd.c -o mycmd -g # debug模式
$ file mycmd
mycmd: ELF 64-bit LSB shared object, x86-64, version 1 (SYSV), dynamically
linked, interpreter /lib64/ld-linux-x86-64.so.2,
BuildID[sha1]=3d5a2317809ef86c7827e9199cfefa622e3c187f, for GNU/Linux
3.2.0, with debug_info, not stripped
7.2.5 演示添加 -g 之后的效果
我们来看一下添加-g之后的效果------
bash复制代码
[Alice@VM-4-17-centos mycmd]$ vim Makefile
[Alice@VM-4-17-centos mycmd]$ make
gcc -o cmd.exe-debug mycmd.c -g
[Alice@VM-4-17-centos mycmd]$ ./cmd.exe-debug
I will begin
running done,result is：[1-100]=5050
[Alice@VM-4-17-centos mycmd]$ ll
total 32
-rwxrwxr-x 1 Alice Alice 8440 Dec 1 00:49 cmd.exe
-rwxrwxr-x 1 Alice Alice 9696 Dec 1 01:07 cmd.exe-debug
-rw-rw-r-- 1 Alice Alice 290 Dec 1 01:07 Makefile
-rw-rw-r-- 1 Alice Alice 345 Dec 1 00:14 mycmd.c
[Alice@VM-4-17-centos mycmd]$ ./cmd.exe
I will begin
running done,result is：[1-100]=5050
[Alice@VM-4-17-centos mycmd]$ ./cmd.exe-debug
I will begin
running done,result is：[1-100]=5050
7.3 怎么证明确实存在调试信息呢？
上面我们说 -g 给形成的可执行程序内部添加调试信息，那怎么证明确实存在调试信息呢？
我们来看看Linux是怎么读取一个二进制文件的格式的------
7.3.1 readelf -S cmd.exe-debug
bash复制代码
[Alice@VM-4-17-centos mycmd]$ readelf -S cmd.exe-debug
There are 35 section headers, starting at offset 0x1d20:
Section Headers:
[Nr] Name Type Address Offset
Size EntSize Flags Link Info Align
[ 0] NULL 0000000000000000 00000000
0000000000000000 0000000000000000 0 0 0
[ 1] .interp PROGBITS 0000000000400238 00000238
000000000000001c 0000000000000000 A 0 0 1
[ 2] .note.ABI-tag NOTE 0000000000400254 00000254
0000000000000020 0000000000000000 A 0 0 4
[ 3] .note.gnu.build-i NOTE 0000000000400274 00000274
0000000000000024 0000000000000000 A 0 0 4
[ 4] .gnu.hash GNU_HASH 0000000000400298 00000298
000000000000001c 0000000000000000 A 5 0 8
[ 5] .dynsym DYNSYM 00000000004002b8 000002b8
0000000000000078 0000000000000018 A 6 1 8
[ 6] .dynstr STRTAB 0000000000400330 00000330
0000000000000044 0000000000000000 A 0 0 1
[ 7] .gnu.version VERSYM 0000000000400374 00000374
000000000000000a 0000000000000002 A 5 0 2
[ 8] .gnu.version_r VERNEED 0000000000400380 00000380
0000000000000020 0000000000000000 A 6 1 8
[ 9] .rela.dyn RELA 00000000004003a0 000003a0
0000000000000018 0000000000000018 A 5 0 8
[10] .rela.plt RELA 00000000004003b8 000003b8
0000000000000060 0000000000000018 AI 5 23 8
[11] .init PROGBITS 0000000000400418 00000418
000000000000001a 0000000000000000 AX 0 0 4
[12] .plt PROGBITS 0000000000400440 00000440
0000000000000050 0000000000000010 AX 0 0 16
[13] .text PROGBITS 0000000000400490 00000490
00000000000001e2 0000000000000000 AX 0 0 16
[14] .fini PROGBITS 0000000000400674 00000674
0000000000000009 0000000000000000 AX 0 0 4
[15] .rodata PROGBITS 0000000000400680 00000680
0000000000000045 0000000000000000 A 0 0 8
[16] .eh_frame_hdr PROGBITS 00000000004006c8 000006c8
000000000000003c 0000000000000000 A 0 0 4
[17] .eh_frame PROGBITS 0000000000400708 00000708
0000000000000114 0000000000000000 A 0 0 8
[18] .init_array INIT_ARRAY 0000000000600e10 00000e10
0000000000000008 0000000000000008 WA 0 0 8
[19] .fini_array FINI_ARRAY 0000000000600e18 00000e18
0000000000000008 0000000000000008 WA 0 0 8
[20] .jcr PROGBITS 0000000000600e20 00000e20
0000000000000008 0000000000000000 WA 0 0 8
[21] .dynamic DYNAMIC 0000000000600e28 00000e28
00000000000001d0 0000000000000010 WA 6 0 8
[22] .got PROGBITS 0000000000600ff8 00000ff8
0000000000000008 0000000000000008 WA 0 0 8
[23] .got.plt PROGBITS 0000000000601000 00001000
0000000000000038 0000000000000008 WA 0 0 8
[24] .data PROGBITS 0000000000601038 00001038
0000000000000004 0000000000000000 WA 0 0 1
[25] .bss NOBITS 000000000060103c 0000103c
0000000000000004 0000000000000000 WA 0 0 1
[26] .comment PROGBITS 0000000000000000 0000103c
000000000000002d 0000000000000001 MS 0 0 1
[27] .debug_aranges PROGBITS 0000000000000000 00001069
0000000000000030 0000000000000000 0 0 1
[28] .debug_info PROGBITS 0000000000000000 00001099
000000000000010e 0000000000000000 0 0 1
[29] .debug_abbrev PROGBITS 0000000000000000 000011a7
000000000000008b 0000000000000000 0 0 1
[30] .debug_line PROGBITS 0000000000000000 00001232
0000000000000059 0000000000000000 0 0 1
[31] .debug_str PROGBITS 0000000000000000 0000128b
00000000000000d1 0000000000000001 MS 0 0 1
[32] .symtab SYMTAB 0000000000000000 00001360
0000000000000690 0000000000000018 33 51 8
[33] .strtab STRTAB 0000000000000000 000019f0
00000000000001e2 0000000000000000 0 0 1
[34] .shstrtab STRTAB 0000000000000000 00001bd2
0000000000000148 0000000000000000 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),
l (large), p (processor specific)
(gdb) b [文件名.后缀名]:[行号] / (gdb) b 21：b + 行号，在21行打一个断点。
(gdb)：用指令查看
我们都演示一下------
dart复制代码
[Alice@VM-4-17-centos linux-git]$ ll
total 36
-rwxrwxr-x 1 Alice Alice 9688 Dec 1 12:35 cmd.exe
drwxrwxr-x 2 Alice Alice 4096 Nov 30 18:03 Jindutiao-2
-rw-rw-r-- 1 Alice Alice 68 Dec 1 12:35 Makefile
drwxrwxr-x 2 Alice Alice 4096 Dec 1 05:14 mycmd
-rw-rw-r-- 1 Alice Alice 345 Dec 1 11:57 mycmd.c
-rw-rw-r-- 1 Alice Alice 848 Nov 30 17:41 README.en.md
-rw-rw-r-- 1 Alice Alice 937 Nov 30 17:41 README.md
[Alice@VM-4-17-centos linux-git]$ gdb cmd.exe
GNU gdb (GDB) Red Hat Enterprise Linux 7.6.1-120.el7
Copyright (C) 2013 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-redhat-linux-gnu".
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>...
Reading symbols from /home/Alice/118/linux-git/cmd.exe...done.
(gdb) l
8 {
9 result += i;
10 }
11
12 return result;
13 }
14
15 int main()
16 {
17 int start = 1;
(gdb)
18 int end = 100;
19 printf("I will begin\n");
20 int n = Sum(start,end);
21 printf("running done,result is：[%d-%d]=%d\n",start,end,n);
22
23 return 0;
24 }
(gdb) l 0
1 #include<stdio.h>
2
3 int Sum(int s,int e)
4 {
5 int result = 0;
6 int i = s;
7 for(;i <= e;i++)
8 {
9 result += i;
10 }
(gdb) l 1
1 #include<stdio.h>
2
3 int Sum(int s,int e)
4 {
5 int result = 0;
6 int i = s;
7 for(;i <= e;i++)
8 {
9 result += i;
10 }
(gdb) r
Starting program: /home/Alice/118/linux-git/cmd.exe
I will begin
running done,result is：[1-100]=5050
[Inferior 1 (process 32157) exited normally]
Missing separate debuginfos, use: debuginfo-install glibc-2.17-326.el7_9.3.x86_64
(gdb) l 0
1 #include<stdio.h>
2
3 int Sum(int s,int e)
4 {
5 int result = 0;
6 int i = s;
7 for(;i <= e;i++)
8 {
9 result += i;
10 }
(gdb)
11
12 return result;
13 }
14
15 int main()
16 {
17 int start = 1;
18 int end = 100;
19 printf("I will begin\n");
20 int n = Sum(start,end);
(gdb)
21 printf("running done,result is：[%d-%d]=%d\n",start,end,n);
22
23 return 0;
24 }
(gdb) b 20
Breakpoint 1 at 0x4005cd: file mycmd.c, line 20.
(gdb) info b
Num Type Disp Enb Address What
1 breakpoint keep y 0x00000000004005cd in main at mycmd.c:20
(gdb) r
Starting program: /home/Alice/118/linux-git/cmd.exe
I will begin
Breakpoint 1, main () at mycmd.c:20
20 int n = Sum(start,end);
(gdb) s
Sum (s=1, e=100) at mycmd.c:5
5 int result = 0;
(gdb) n
6 int i = s;
(gdb) n
7 for(;i <= e;i++)
(gdb) n
9 result += i;
(gdb)
7 for(;i <= e;i++)
(gdb)
9 result += i;
(gdb)
7 for(;i <= e;i++)
(gdb) p result
$1 = 3
(gdb) p &result
$2 = (int *) 0x7fffffffe40c
(gdb) n
9 result += i;
(gdb) n
7 for(;i <= e;i++)
(gdb) n
9 result += i;
(gdb) display result
1: result = 6
(gdb)
(gdb)
(gdb)
(gdb)
(gdb)
(gdb) n
7 for(;i <= e;i++)
1: result = 10
(gdb) n
9 result += i;
1: result = 10
(gdb) n
7 for(;i <= e;i++)
1: result = 15
(gdb) n
9 result += i;
1: result = 15
(gdb) n
7 for(;i <= e;i++)
1: result = 21
(gdb) n
9 result += i;
1: result = 21
(gdb) n
7 for(;i <= e;i++)
1: result = 28
(gdb)
9 result += i;
1: result = 28
(gdb)
7 for(;i <= e;i++)
1: result = 36
(gdb)
9 result += i;
1: result = 36
(gdb)
7 for(;i <= e;i++)
1: result = 45
(gdb)
9 result += i;
1: result = 45
(gdb)
7 for(;i <= e;i++)
1: result = 55
(gdb)
9 result += i;
1: result = 55
(gdb)
7 for(;i <= e;i++)
1: result = 66
(gdb)
9 result += i;
1: result = 66
(gdb)
7 for(;i <= e;i++)
1: result = 78
(gdb)
9 result += i;
1: result = 78
(gdb) quit
A debugging session is active.
Inferior 1 [process 32288] will be killed.
Quit anyway? (y or n) y
7.6.3 cgdb的使用
7.6.4 打断点和删除断点
Linux操作系统下，打断点和删除断点------
dart复制代码
[Alice@VM-4-17-centos linux-git]$ gdb ./process_bar
GNU gdb (GDB) Red Hat Enterprise Linux 7.6.1-120.el7
Copyright (C) 2013 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-redhat-linux-gnu".
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>...
Reading symbols from /home/Alice/118/linux-git/process_bar...(no debugging symbols found)...done.
(gdb) l
No symbol table is loaded. Use the "file" command.
(gdb) list
No symbol table is loaded. Use the "file" command.
(gdb) r
Starting program: /home/Alice/118/linux-git/./process_bar
I will begin
running done,result is：[1-100]=5050
[Inferior 1 (process 12969) exited normally]
Missing separate debuginfos, use: debuginfo-install glibc-2.17-326.el7_9.3.x86_64
(gdb) b
No default breakpoint address now.
(gdb) b mycmd.c:20
No symbol table is loaded. Use the "file" command.
Make breakpoint pending on future shared library load? (y or [n]) y
Breakpoint 1 (mycmd.c:20) pending.
(gdb) b 21
No symbol table is loaded. Use the "file" command.
(gdb) info b
Num Type Disp Enb Address What
1 breakpoint keep y <PENDING> mycmd.c:20
(gdb) b 21
No symbol table is loaded. Use the "file" command.
(gdb) breakpoint 21
Undefined command: "breakpoint". Try "help".
(gdb) d 1
(gdb) info b
No breakpoints or watchpoints.
(gdb) quit
(gdb) b 21
Breakpoint 2 at 0x4005df: file mycmd.c, line 21.
(gdb) b 18
Breakpoint 3 at 0x4005bc: file mycmd.c, line 18.
(gdb) info b
Num Type Disp Enb Address What
1 breakpoint keep y 0x00000000004005a8 in Sum at mycmd.c:12
2 breakpoint keep y 0x00000000004005df in main at mycmd.c:21
3 breakpoint keep y 0x00000000004005bc in main at mycmd.c:18
(gdb) d 3
(gdb) info b
Num Type Disp Enb Address What
1 breakpoint keep y 0x00000000004005a8 in Sum at mycmd.c:12
2 breakpoint keep y 0x00000000004005df in main at mycmd.c:21
(gdb) b 19
Breakpoint 4 at 0x4005c3: file mycmd.c, line 19.
(gdb) info b
Num Type Disp Enb Address What
1 breakpoint keep y 0x00000000004005a8 in Sum at mycmd.c:12
2 breakpoint keep y 0x00000000004005df in main at mycmd.c:21
4 breakpoint keep y 0x00000000004005c3 in main at mycmd.c:19
(gdb) l main
11
12 return result;
13 }
14
15 int main()
16 {
17 int start = 1;
18 int end = 100;
19 printf("I will begin\n");
20 int n = Sum(start, end);
(gdb) b 20
Breakpoint 1 at 0x11c3: file mycmd.c, line 20.
(gdb) info b
Num Type Disp Enb Address What
1 breakpoint keep y 0x00000000000011c3 in main at mycmd.c:20
(gdb) r
Starting program: /home/whb/test/test/mycmd
I will begin
Breakpoint 1, main () at mycmd.c:20
20 int n = Sum(start, end);
(gdb) s
Sum (s=32767, e=-7136) at mycmd.c:5
5 {
(gdb) n
6 int result = 0;
(gdb) watch result
Hardware watchpoint 2: result
(gdb) c
Continuing.
Hardware watchpoint 2: result
Old value = -6896
New value = 0
Sum (s=1, e=100) at mycmd.c:7
7 for(int i = s; i <= e; i++)
(gdb) c
Continuing.
Hardware watchpoint 2: result
Old value = 0
New value = 1
Sum (s=1, e=100) at mycmd.c:7
7 for(int i = s; i <= e; i++)
(gdb) c
Continuing.
Hardware watchpoint 2: result
Old value = 1
New value = 3
Sum (s=1, e=100) at mycmd.c:7
7 for(int i = s; i <= e; i++)
(gdb) c
Continuing.
Hardware watchpoint 2: result
Old value = 3
New value = 6
Sum (s=1, e=100) at mycmd.c:7
7 for(int i = s; i <= e; i++)
(gdb) info b
Num Type Disp Enb Address What
1 breakpoint keep y 0x00005555555551c3 in main at mycmd.c:20
breakpoint already hit 1 time
2 hw watchpoint keep y result
breakpoint already hit 4 times
(gdb) d 2
(gdb) info b
Num Type Disp Enb Address What
1 breakpoint keep y 0x00005555555551c3 in main at mycmd.c:20
breakpoint already hit 1 time
(gdb) finish
Run till exit from #0 Sum (s=1, e=100) at mycmd.c:7
0x00005555555551d2 in main () at mycmd.c:20
20 int n = Sum(start, end);
Value returned is $1 = 5050
因此，watch常用于监视指针。
7.7.2 确定问题原因并且验证原因：set var
set var：可以直接在调试期间修改变量。
更改一下标志位（比如flag，+1 / -1这种），假设我们想得到+-result。
我们举个例子，比如set var
c复制代码
// mycmd.c
#include <stdio.h>
int flag = 0; // 故意错误
//int flag = -1;
//int flag = 1;
int Sum(int s, int e)
{
int result = 0;
for(int i = s; i <= e; i++)
{
result += i;
}
return result*flag;
}
int main()
{
int start = 1;
int end = 100;
printf("I will begin\n");
int n = Sum(start, end);
printf("running done, result is: [%d-%d]=%d\n", start, end, n);
return 0;
}
bash复制代码
(gdb) l main
15
16 return result*flag;
17 }
18
19 int main()
20 {
21 int start = 1;
22 int end = 100;
23 printf("I will begin\n");
24 int n = Sum(start, end);
(gdb) b 24
Breakpoint 1 at 0x11ca: file mycmd.c, line 24.
(gdb) r
Starting program: /home/whb/test/test/mycmd
I will begin
Breakpoint 1, main () at mycmd.c:24
24 int n = Sum(start, end);
(gdb) n
25 printf("running done, result is: [%d-%d]=%d\n", start, end,
n);
(gdb) n
running done, result is: [1-100]=0 # 这⾥结果为什么是0？
26 return 0;
(gdb) r
The program being debugged has been started already.
Start it from the beginning? (y or n) y
Starting program: /home/whb/test/test/mycmd
I will begin
Breakpoint 1, main () at mycmd.c:24
24 int n = Sum(start, end);
(gdb) s
Sum (s=32767, e=-7136) at mycmd.c:9
9 {
(gdb) n
10 int result = 0;
(gdb) n
11 for(int i = s; i <= e; i++)
(gdb)
13 result += i;
(gdb)
11 for(int i = s; i <= e; i++)
(gdb)
13 result += i;
(gdb) until 14
Sum (s=1, e=100) at mycmd.c:16
16 return result*flag;
(gdb) p result
$1 = 5050
(gdb) p flag
$2 = 0
(gdb) set var flag=1 # 更改flag的值，确认是否是它的原因
(gdb) p flag
$3 = 1
(gdb) n
17 }
(gdb) n
main () at mycmd.c:25
25 printf("running done, result is: [%d-%d]=%d\n", start, end,
n);
(gdb) n
running done, result is: [1-100]=5050 # 是它的原因
26 return 0;
7.7.3 条件断点（也是断点）
条件断点的类型和普通断点一样，也是breakpoint，多了个条件------"stop only . . .（[条件]）"
7.7.3.1 添加条件断点
bash复制代码
(gdb) l main
11
12 return result;
13 }
14
15 int main()
16 {
17 int start = 1;
18 int end = 100;
19 printf("I will begin\n");
20 int n = Sum(start, end);
(gdb) b 20
Breakpoint 1 at 0x11c3: file mycmd.c, line 20.
(gdb) r
Starting program: /home/whb/test/test/mycmd
I will begin
Breakpoint 1, main () at mycmd.c:20
20 int n = Sum(start, end);
(gdb) s
Sum (s=32767, e=-7136) at mycmd.c:5
5 {
(gdb) n
6 int result = 0;
(gdb) n
7 for(int i = s; i <= e; i++)
(gdb) n
9 result += i;
(gdb) display i
1: i = 1
(gdb) n
7 for(int i = s; i <= e; i++)
1: i = 1
(gdb) n
9 result += i;
1: i = 2
(gdb) n
7 for(int i = s; i <= e; i++)
1: i = 2
(gdb) n
9 result += i;
1: i = 3
(gdb)
7 for(int i = s; i <= e; i++)
1: i = 3
(gdb) info b
Num Type Disp Enb Address What
1 breakpoint keep y 0x00005555555551c3 in main at mycmd.c:20
breakpoint already hit 1 time
(gdb) b 9 if i == 30 # 9是⾏号，表⽰新增断点的位置
Breakpoint 2 at 0x555555555186: file mycmd.c, line 9.
(gdb) info b
Num Type Disp Enb Address What
1 breakpoint keep y 0x00005555555551c3 in main at mycmd.c:20
breakpoint already hit 1 time
2 breakpoint keep y 0x0000555555555186 in Sum at mycmd.c:9
stop only if i == 30
(gdb) finish
Run till exit from #0 Sum (s=1, e=100) at mycmd.c:7
Breakpoint 2, Sum (s=1, e=100) at mycmd.c:9
9 result += i;
1: i = 30
(gdb) finish
Run till exit from #0 Sum (s=1, e=100) at mycmd.c:9
0x00005555555551d2 in main () at mycmd.c:20
20 int n = Sum(start, end);
Value returned is $1 = 5050
7.7.3.2 给已经存在的断点新增条件
bash复制代码
(gdb) l main
11
12 return result;
13 }
14
15 int main()
16 {
17 int start = 1;
18 int end = 100;
19 printf("I will begin\n");
20 int n = Sum(start, end);
(gdb) b 20
Breakpoint 1 at 0x11c3: file mycmd.c, line 20.
(gdb) r
Starting program: /home/whb/test/test/mycmd
I will begin
Breakpoint 1, main () at mycmd.c:20
20 int n = Sum(start, end);
(gdb) s
Sum (s=32767, e=-7136) at mycmd.c:5
5 {
(gdb) n
6 int result = 0;
(gdb) n
7 for(int i = s; i <= e; i++)
(gdb) n
9 result += i;
(gdb)
7 for(int i = s; i <= e; i++)
(gdb)
9 result += i;
(gdb)
7 for(int i = s; i <= e; i++)
(gdb)
9 result += i;
(gdb)
7 for(int i = s; i <= e; i++)
(gdb) b 9 # 我们在第9⾏新增⼀个断点，⽤来开始测试
Breakpoint 2 at 0x555555555186: file mycmd.c, line 9.
(gdb) info b
Num Type Disp Enb Address What
1 breakpoint keep y 0x00005555555551c3 in main at mycmd.c:20
breakpoint already hit 1 time
2 breakpoint keep y 0x0000555555555186 in Sum at mycmd.c:9
(gdb) n
Breakpoint 2, Sum (s=1, e=100) at mycmd.c:9
9 result += i;
(gdb) n
7 for(int i = s; i <= e; i++)
(gdb) n
Breakpoint 2, Sum (s=1, e=100) at mycmd.c:9
9 result += i;
(gdb) condition 2 i==30 #给2号断点，新增条件i==30
(gdb) info b
Num Type Disp Enb Address What
1 breakpoint keep y 0x00005555555551c3 in main at mycmd.c:20
breakpoint already hit 1 time
2 breakpoint keep y 0x0000555555555186 in Sum at mycmd.c:9
stop only if i==30
breakpoint already hit 2 times
(gdb) n
7 for(int i = s; i <= e; i++)
(gdb) n
9 result += i;
(gdb) c
Continuing.
Breakpoint 2, Sum (s=1, e=100) at mycmd.c:9
9 result += i;
(gdb) p i
$1 = 30
(gdb) p result
$2 = 435
