gdb调试器的使用

一重要准备

要使用gdb来调试程序，最重要的准备是在编译C/C++程序的时候，把调试信息加到可执行文件中。加上-g选项可以做到这一点。比如：

gcc -g test.c -o test

如果没有-g，将看不见程序的函数名、变量名，所代替的全是运行时的内存地址。所以，如果要用gdb调试程序，就要在编译的时候使用-g。

二启动gdb

1 一般启动和退出方法

[root@localhost ~]# gdb
GNU gdb (GDB) Red Hat Enterprise Linux 7.6.1-100.el7_4.1
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/>.
(gdb) q

2 启动的时候加载一个在编译时没加-g的可执行文件

[root@localhost test]# g++ test.cpp -o test
[root@localhost test]# gdb test
GNU gdb (GDB) Red Hat Enterprise Linux 7.6.1-100.el7_4.1
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/C++/ch02/2.5/test/test...(no debugging symbols found)...done.

由于test在编译的时候没有选项-g，因此gdb提示(no debugging symbols found)。

3 启动的时候加载一个在编译时加了-g的可执行文件

[root@localhost test]# g++ test.cpp -g -o test
[root@localhost test]# gdb test
GNU gdb (GDB) Red Hat Enterprise Linux 7.6.1-100.el7_4.1
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/C++/ch02/2.5/test/test...done.

4 gdb <program> core

用gdb同时调试一个运行程序和core文件，core是程序非法执行core dump后产生的文件。

5 gdb <program> <PID>

如果我们的程序是一个服务程序（守护程序），那么可以指定这个服务程序运行时的进程ID。gdb会自动attach上去，并调试它。program应该在PATH环境中搜索得到。

三帮助

1 格式

help <command>

2 举例

(gdb) help breakpoints
Making program stop at certain points.

List of commands:

awatch -- Set a watchpoint for an expression
break -- Set breakpoint at specified line or function
break-range -- Set a breakpoint for an address range
catch -- Set catchpoints to catch events
catch assert -- Catch failed Ada assertions
catch catch -- Catch an exception
catch exception -- Catch Ada exceptions
catch exec -- Catch calls to exec
catch fork -- Catch calls to fork
catch load -- Catch loads of shared libraries
catch signal -- Catch signals by their names and/or numbers
catch syscall -- Catch system calls by their names and/or numbers
catch throw -- Catch an exception
catch unload -- Catch unloads of shared libraries
catch vfork -- Catch calls to vfork
clear -- Clear breakpoint at specified line or function
commands -- Set commands to be executed when a breakpoint is hit
condition -- Specify breakpoint number N to break only if COND is true
delete -- Delete some breakpoints or auto-display expressions
delete bookmark -- Delete a bookmark from the bookmark list
delete breakpoints -- Delete some breakpoints or auto-display expressions
delete checkpoint -- Delete a checkpoint (experimental)
delete display -- Cancel some expressions to be displayed when program stops
delete mem -- Delete memory region
delete tracepoints -- Delete specified tracepoints
delete tvariable -- Delete one or more trace state variables
disable -- Disable some breakpoints
disable breakpoints -- Disable some breakpoints
disable display -- Disable some expressions to be displayed when program stops
disable frame-filter -- GDB command to disable the specified frame-filter
disable mem -- Disable memory region
disable pretty-printer -- GDB command to disable the specified pretty-printer

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