我正在Linux平台上构建一个C应用程序。我需要使用libmysqlclient来连接数据库。
我下载了Linux源代码包mysql-connector-c-6.0.2.tar.gz。我按照说明编译了它。我得到以下库:
libmysqlclient.a libmysqlclient.so libmysql.so.16
libmysqlclient_r.so libmysql.so libmysql.so.16.0.0
如果我的应用程序是多线程的,我可以将我的应用程序与libmysqlclient.a链接吗?根据mysql文档(http://forge.mysql.com/wiki/Autotools_to_CMake_Transition_Guide),使用cmake工具,客户端始终是线程安全的。
将我的应用程序与libmysqlclient.a链接后,我的应用程序中出现了以下调用堆栈的崩溃:
#0 0x0867878a in my_stat ()
No symbol table info available.
#1 0x08671611 in init_available_charsets.clone.0 ()
No symbol table info available.
#2 0x086720d5 in get_charset_by_csname ()
No symbol table info available.
#3 0x086522af in mysql_init_character_set ()
No symbol table info available.
#4 0x0865266d in mysql_real_connect ()
在我的应用程序中,我在线程函数中有以下代码:
if (NULL == (pMySQL = mysql_init(NULL)))
{
return -1;
}
if (NULL == mysql_real_connect(pMySQL, ServerName, UserName, Password, Name, Port, NULL, 0))
{
mysql_close(pMySQL);
return -1;
}
if (0 != mysql_query(pMySQL, pQuery))
{
mysql_close(pMySQL);
return -1;
}
mysql_close(pMySQL);
我没有使用libmysqlclient_r.so,因为我想静态链接到mysql客户端库。有没有办法用cmake生成libmysqlclient_r.a?
更新
没有做任何其他事情,我只是将mysql客户端构建类型更改为debug。现在我在mysql_init()函数中崩溃了。
在应用程序控制台上,我得到以下打印:
safe_mutex: Trying to lock unitialized mutex at /install/mysqlconnc/mysql-connector-c-6.0.2/mysys/safemalloc.c, line 520
崩溃的调用堆栈如下:
#0 0x00556430 in __kernel_vsyscall ()
No symbol table info available.
#1 0x45fdf2f1 in raise () from /lib/libc.so.6
No symbol table info available.
#2 0x45fe0d5e in abort () from /lib/libc.so.6
No symbol table info available.
#3 0x086833e5 in safe_mutex_lock (mp=0x915e8e0, my_flags=0,
file=0x895b9d8 "/install/mysqlconnc/mysql-connector-c-6.0.2/mysys/safemalloc.c", line=520)
at /install/mysqlconnc/mysql-connector-c-6.0.2/mysys/thr_mutex.c:178
error = 140915306
__PRETTY_FUNCTION__ = "safe_mutex_lock"
#4 0x08682715 in _sanity (
filename=0x895a87c "/install/mysqlconnc/mysql-connector-c-6.0.2/mysys/my_error.c", lineno=195)
at /install/mysqlconnc/mysql-connector-c-6.0.2/mysys/safemalloc.c:520
irem = 0xf2300468
flag = 0
count = 0
#5 0x0868186b in _mymalloc (size=16,
filename=0x895a87c "/install/mysqlconnc/mysql-connector-c-6.0.2/mysys/my_error.c", lineno=195, MyFlags=16)
at /install/mysqlconnc/mysql-connector-c-6.0.2/mysys/safemalloc.c:130
irem = 0x0
data = 0x0
_db_stack_frame_ = {func = 0x6d617266 <Address 0x6d617266 out of bounds>, file = 0x65685f65 <Address 0x65685f65 out of bounds>,
level = 0, prev = 0x0}
#6 0x0867e0e1 in my_error_register (errmsgs=0x89a7760, first=2000, last=2058)
at /install/mysqlconnc/mysql-connector-c-6.0.2/mysys/my_error.c:194
meh_p = 0x46087568
search_meh_pp = 0x1000
#7 0x08655f7e in init_client_errs ()
at /install/mysqlconnc/mysql-connector-c-6.0.2/libmysql/errmsg.c:238
No locals.
#8 0x08655fe3 in mysql_server_init (argc=0, argv=0x0, groups=0x0)
at /install/mysqlconnc/mysql-connector-c-6.0.2/libmysql/libmysql.c:128
result = 0
#9 0x08651fc0 in mysql_init (mysql=0x0)
at /install/mysqlconnc/mysql-connector-c-6.0.2/libmysql/client.c:1606
解决方案:
我在创建线程之前调用mysql_library_init(),并在终止线程后调用mysql_library_end()。在每个线程中,我在线程函数的开头调用mysql_thread_init()并在线程函数结束时调用mysql_thread_end()。这解决了崩溃的问题。
答案 0 :(得分:3)
<强>更新强>:
您似乎需要在mysql_init()
之前致电mysql_library_init():
你必须要么调用mysql_library_init() 在产生任何线程之前,或者使用互斥锁来保护线程 调用,无论是调用mysql_library_init()还是间接调用 mysql_init()。在任何其他客户端库调用之前执行此操作。
关于您的原始问题,libmysqlclient_r.so
实际上是libmysql.so
的符号链接。您可以更改libmysql/CMakeLists.txt
以生成静态库(libmysql.a
),而不是从以下行中删除SHARED
关键字:
ADD_LIBRARY(libmysql SHARED ${CLIENT_SOURCES} libmysql.def)
但是,我建议(1)尝试在不使用线程的情况下运行相同的代码,看看问题是否仍然存在,(2)构建和使用库的调试版本:
cmake -G "Unix Makefiles" -DCMAKE_BUILD_TYPE=Debug
make
通过这种方式,您可以更详细地调查此问题。