Linux GDB调试

1、什么是GDB

2、准备工作

3、GDB启动、退出、查看代码

输入：

gcc test.c -o test -g
gcc test.c -o test1
ll -h test test1
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输出：

-rwxr-xr-x 1 petri petri 20K Apr 21 18:50 test*
-rwxr-xr-x 1 petri petri 17K Apr 21 18:50 test1*
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可以看出加入-g文件变大了。

进入gdb调试：

gdb test
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(gdb) set args 10 20
(gdb) show args
Argument list to give program being debugged when it is started is "10 20".
(gdb) help （查看帮助文档）
(gdb) q (退出）
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关于list：

-g 选项的作用是在可执行文件中加入源代码信息，比如可执行文件中第几条机器指令对应源代码的第几行，并没有把源代码嵌入可执行文件中。所以源代码文件不可以没有。

1、显示
list 一次显示10行：

(gdb) list
1       #include <stdio.h>
2       #include <stdlib.h>
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4       int test(int a);
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6       int main(int argc, char* argv[]) {
7           int a, b;
8           printf("argc = %d\n", argc);
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10          if(argc < 3) {
(gdb) list
11              a = 10;
12              b = 30;
13          } else {
14              a = atoi(argv[1]);
15              b = atoi(argv[2]);
16          }
17          printf("a = %d, b = %d\n", a, b);
18          printf("a + b = %d\n", a + b);
19
20          for(int i = 0; i < a; ++i) {
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(gdb) list 10 （第十行开始显示）

(gdb) list main （main函数开始显示）

(gdb) list bubble.cpp:10  （通过文件名：行号）

(gdb) list select.cpp:selectSort （通过文件名：函数） 
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2、设置显示行数

(gdb) show list
Number of source lines gdb will list by default is 10.
(gdb) set list 20
(gdb) show list
Number of source lines gdb will list by default is 20.
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4、GDB打断点

(gdb) break 10
Breakpoint 1 at 0x11b2: file test.c, line 10

(gdb) d 1

(gdb) i b
No breakpoints or watchpoints.

(gdb) break 11
Breakpoint 2 at 0x11b2: file test.c, line 11.

(gdb) disable 2

(gdb) enable 2

(gdb) info break
Num     Type           Disp Enb Address            What
2       breakpoint     keep y   0x00000000000011b2 in main at test.c:11

(gdb) break 21 if i=3
Breakpoint 3 at 0x1231: file test.c, line 21.

(gdb) info break
Num     Type           Disp Enb Address            What
2       breakpoint     keep y   0x00000000000011b2 in main at test.c:11
3       breakpoint     keep y   0x0000000000001231 in main at test.c:21
        stop only if i=3
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5、GDB调试命令

(gdb) start
Temporary breakpoint 4 at 0x1189: file test.c, line 6.
Starting program: /home/petri/lesson01/03_gdb/test 

Temporary breakpoint 4, main (argc=0, argv=0x0) at test.c:6
6       int main(int argc, char* argv[]) {

(gdb) run
The program being debugged has been started already.
Start it from the beginning? (y or n) y
Starting program: /home/petri/lesson01/03_gdb/test 
argc = 1

Breakpoint 2, main (argc=1, argv=0x7ffffffedc78) at test.c:10
10          if(argc < 3) {

(gdb) continue
Continuing.
a = 10, b = 30
a + b = 40

Breakpoint 3, main (argc=1, argv=0x7ffffffedc78) at test.c:21
21              printf("i = %d\n", i);
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test.c的代码：

#include 
#include 

int test(int a);

int main(int argc, char* argv[]) {
    int a, b;
    printf("argc = %d\n", argc);

    if(argc < 3) {
        a = 10;
        b = 30;
    } else {
        a = atoi(argv[1]);
        b = atoi(argv[2]);
    }
    printf("a = %d, b = %d\n", a, b);
    printf("a + b = %d\n", a + b);

    for(int i = 0; i < a; ++i) {
        printf("i = %d\n", i);
        // 函数调用
        int res = test(i);
        printf("res value: %d\n", res);
    }

    printf("THE END !!!\n");
    return 0;
}

int test(int a) {
    int num = 0;
    for(int i = 0; i < a; ++i) {
        num += i;
    }
    return num;
}

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