gdb给指定位置设置断点

1. 说明

   • gdb断点

     • 有三种: 模糊行级匹配,精确行级匹配,指令级匹配.

   • 模糊行级匹配

     • 即断点是在某行,但是给的表达式可以匹配多个行.
     • 即设置了多个断点.

   • 精确行级匹配

     • 同上,去除上面的二义性.

   • 指令级匹配

     • 断点精确到具体的某个指令,虽然最终也会落在某行.

2. 模糊行级匹配

   • 代码

     int a = 0;
     void show(int) {
        a += 2;
     }
     void show() {
        a ++;
     }
     int main() {
        show(1);
        show(2);
        return 0;
     }
     

   • 编译调试

     [root@localhost temp]# g++ test.cpp -g
     [root@localhost temp]# gdb ./a.out
     GNU gdb (GDB) Red Hat Enterprise Linux 7.6.1-119.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".a
     For bug reporting instructions, please see:
     <http://www.gnu.org/software/gdb/bugs/>...
     Reading symbols from /root/cfile/temp/a.out...done.
     (gdb) break show
     Breakpoint 1 at 0x400514: show. (2 locations)
     (gdb) info breakpoints
     Num     Type           Disp Enb Address            What
     1       breakpoint     keep y   <MULTIPLE>
     1.1                         y     0x0000000000400514 in show(int) at test.cpp:3
     1.2                         y     0x0000000000400529 in show() at test.cpp:6
     (gdb)
     
     

     • 可以看到break show设置断点添加了两个断点.

3. 精确行级匹配

   • 说明

     • gdb需要升级才支持.与gcc4.8.5配对的不支持.

   • 升级

     • 下载 wget https://repo.huaweicloud.com/centos/7/sclo/x86_64/rh/Packages/d/devtoolset-7-gdb-8.0-17.el7.x86_64.rpm
     • 配置 yum install ./devtoolset-7-gdb-8.0-17.el7.x86_64.rpm
     • 安装 yum install devtoolset-7-gdb.x86_64 -y

   • 指定

     [root@localhost temp]# /opt/rh/devtoolset-7/root/usr/bin/gdb a.out
     GNU gdb (GDB) Red Hat Enterprise Linux 8.0.1-36.el7
     Copyright (C) 2017 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".
     Type "show configuration" for configuration details.
     For bug reporting instructions, please see:
     <http://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 a.out...done.
     (gdb) break -source test.cpp -function show -line 3
     Breakpoint 1 at 0x400514: file test.cpp, line 3.
     (gdb) info breakpoints
     Num     Type           Disp Enb Address            What
     1       breakpoint     keep y   0x0000000000400514 in show(int) at test.cpp:3
     (gdb)
     
     

   • 说明

     • 支持指定source源文件,-function函数,-line行号,-label跳转位置.

4. 指令级断点

   • 说明

     • 通过反汇编获取虚拟地址,设置对应位置的断点.

     • 注意指令前面加 * .

   • 案例

     [root@localhost temp]# gdb ./a.out
     GNU gdb (GDB) Red Hat Enterprise Linux 7.6.1-119.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 /root/cfile/temp/a.out...done.
     (gdb) disassemble show
     Dump of assembler code for function show(int):
       0x000000000040050d <+0>:     push   %rbp
       0x000000000040050e <+1>:     mov    %rsp,%rbp
       0x0000000000400511 <+4>:     mov    %edi,-0x4(%rbp)
       0x0000000000400514 <+7>:     mov    0x200b16(%rip),%eax        # 0x601030 <a>
       0x000000000040051a <+13>:    add    $0x2,%eax
       0x000000000040051d <+16>:    mov    %eax,0x200b0d(%rip)        # 0x601030 <a>
       0x0000000000400523 <+22>:    pop    %rbp
       0x0000000000400524 <+23>:    retq
     End of assembler dump.
     (gdb) break *0x000000000040050e
     Breakpoint 1 at 0x40050e: file test.cpp, line 2.
     
     

5. 总结

   • 转化为行显示断点位置.
   • 多种指定方式,模糊到精确,简单到复杂.