欢迎您访问程序员文章站本站旨在为大家提供分享程序员计算机编程知识!
您现在的位置是: 首页  >  数据库

Mysql的Debug模式实现_MySQL

程序员文章站 2022-05-20 15:20:07
...
bitsCN.com

Mysql的Debug模式实现

前一段领导开发了一个内核的模块,测试的过程中,发现导致MYSQL客户端无法连接服务器。

经过查询文档,追根溯源,终于找到了MYSQL实现链接客户端的代码,在源文件sql-common/client.c里的 CLI_MYSQL_REAL_CONNECT 函数。

但是代码很长,一时半会儿肯定看不明白。这个时候发现,发现代码当中有很多这样的代码:

[cpp]

DBUG_ENTER("mysql_real_connect");

说明只要以调试模式启动MYSQL,就可以跟踪代码的执行。

经过查询文档和测试,只要在 cmake 的时候,增加参数 cmake -WITH_DEBUG=1 就可以了。

然后启动一个MYSQL客户端程序之前,更改一个环境变量:

[plain]

export MYSQL_DEBUG=d:t:O,/tmp/client.trace

使用编辑器打开 /tmp/client.trace 就会得到这样的Debug信息:

[cpp]

| info: Connect socket

| >vio_socket_connect

| | >vio_set_blocking

| |

| | >vio_io_wait

| |

| | >vio_set_blocking

| |

|

| info: No success, close socket, try next address.

| info: End of connect attempts, sock: 4 status: 1 error: 0

| error: Got error 0 on connect to 'localhost'

| >set_mysql_extended_error

| | enter: error :2003 'Can't connect to MySQL server on '%-.100s' (%d)'

|

| error: message: 2003/HY000 (Can't connect to MySQL server on 'localhost' (0))

后面的数字是行号。从这个文件就可以追踪程序的执行啦!

好牛逼啊!我们不禁感叹。之余,学习了一下这个调试模式的具体实现:

在 CMakeList.txt 中,有这么一段代码:

[plain]

IF(WITH_DEBUG)

SET(CMAKE_BUILD_TYPE "Debug" CACHE STRING ${BUILDTYPE_DOCSTRING} FORCE)

[plain]

IF(NOT CMAKE_BUILD_TYPE

AND NOT CMAKE_GENERATOR MATCHES "Visual Studio"

AND NOT CMAKE_GENERATOR MATCHES "Xcode")

# This is the case of no CMAKE_BUILD_TYPE choosen, typical for VS and Xcode

# or if custom C flags are set. In VS and Xcode for non-Debug configurations

# DBUG_OFF is already correctly set. Use DBUG_OFF for Makefile based projects

# without build type too, unless user specifically requests DBUG.

IF(NOT CMAKE_C_FLAGS MATCHES "-DDBUG_ON")

ADD_DEFINITIONS(-DDBUG_OFF)

ENDIF()

ENDIF()

如果没有设置 CMAKE_BUILD_TYPE ,那么就会执行下面一段代码。如果这时候也没有设置一个名为-DDBUG_ON的CFLAGS的环境变量的话,就会增加一个CFLAGS:-DDBUG_OFF。

之后,当编译器编译的时候,根据编译器的参数增加的宏来决定 怎么定义 DBUG_ENTER 之类的函数是空代码,还是实际的报错代码。

[cpp]

/*

* These macros provide a user interface into functions in the

* dbug runtime support library. They isolate users from changes

* in the MACROS and/or runtime support.

*

* The symbols "__LINE__" and "__FILE__" are expanded by the

* preprocessor to the current source file line number and file

* name respectively.

*

* WARNING --- Because the DBUG_ENTER macro allocates space on

* the user function's stack, it must precede any executable

* statements in the user function.

*

*/

# ifdef DBUG_OFF

# define DBUG_ENTER(a1)

# define DBUG_RETURN(a1) return(a1)

# define DBUG_VOID_RETURN return

# define DBUG_EXECUTE(keyword,a1)

# define DBUG_PRINT(keyword,arglist)

# define DBUG_2(keyword,format) /* Obsolete */

# define DBUG_3(keyword,format,a1) /* Obsolete */

# define DBUG_4(keyword,format,a1,a2) /* Obsolete */

# define DBUG_5(keyword,format,a1,a2,a3) /* Obsolete */

# define DBUG_PUSH(a1)

# define DBUG_POP()

# define DBUG_PROCESS(a1)

# define DBUG_FILE (stderr)

# define DBUG_SETJMP setjmp

# define DBUG_LONGJMP longjmp

# define DBUG_DUMP(keyword,a1)

# else

# define DBUG_ENTER(a) /

auto char *_db_func_; auto char *_db_file_; auto int _db_level_; /

auto char **_db_framep_; /

_db_enter_ (a,__FILE__,__LINE__,&_db_func_,&_db_file_,&_db_level_, /

&_db_framep_)

# define DBUG_LEAVE /

(_db_return_ (__LINE__, &_db_func_, &_db_file_, &_db_level_))

# define DBUG_RETURN(a1) return (DBUG_LEAVE, (a1))

# define DBUG_VOID_RETURN {DBUG_LEAVE; return;}

# define DBUG_EXECUTE(keyword,a1) /

{if (_db_on_) {if (_db_keyword_ (keyword)) { a1 }}}

# define DBUG_PRINT(keyword,arglist) /

{if (_db_on_) {_db_pargs_(__LINE__,keyword); _db_doprnt_ arglist;}}

# define DBUG_2(keyword,format) /

DBUG_PRINT(keyword,(format)) /* Obsolete */

# define DBUG_3(keyword,format,a1) /

DBUG_PRINT(keyword,(format,a1)) /* Obsolete */

# define DBUG_4(keyword,format,a1,a2) /

DBUG_PRINT(keyword,(format,a1,a2)) /* Obsolete */

# define DBUG_5(keyword,format,a1,a2,a3) /

DBUG_PRINT(keyword,(format,a1,a2,a3)) /* Obsolete */

# define DBUG_PUSH(a1) _db_push_ (a1)

# define DBUG_POP() _db_pop_ ()

# define DBUG_PROCESS(a1) (_db_process_ = a1)

# define DBUG_FILE (_db_fp_)

# define DBUG_SETJMP(a1) (_db_setjmp_ (), setjmp (a1))

# define DBUG_LONGJMP(a1,a2) (_db_longjmp_ (), longjmp (a1, a2))

# define DBUG_DUMP(keyword,a1,a2) _db_dump_(__LINE__,keyword,a1,a2)

# endif

bitsCN.com