之前已经一步步从源码编译完成了mysql，参考链接mysql编译安装全过程，现在开始对mysql做调试，了解内部的运行细节
学习gdb的使用
如果对gdb不是很熟悉，先初步了解gdb的使用
准备环境
gcc5.5安装，gdb安装，以及LD_LIBRARY_PATH设置
export LD_LIBRARY_PATH=/usr/local/gcc-5.5.0/lib64
开始调试
# gdb mysqld
GNU gdb (GDB) Red Hat Enterprise Linux 7.6.1-114.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 /usr/local/mysql8017/bin/mysqld...done.
(gdb) l
16 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
17 GNU General Public License, version 2.0, for more details.
18
19 You should have received a copy of the GNU General Public License
20 along with this program; if not, write to the Free Software
21 Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA */
22
23 extern int mysqld_main(int argc, char **argv);
24
25 int main(int argc, char **argv) { return mysqld_main(argc, argv); }
运行mysqld
#(gdb) r --defaults-file=/data/mysql8017/my.cnf --user=mysql
如果我们不设置任何断点，就和普通的mysql运行没有区别，也可以使用mysql客户端登录并执行操作。那为了明确代码细节，先设置断点看看
