旧版MySQL Connector C ++使用sql :: ConnectOptionsMap异常 [英] Legacy MySQL Connector C++ using sql::ConnectOptionsMap exception

问题描述

已经2天了，我试图了解为什么会发生这种情况，但是我没有足够的调试技巧来了解为什么会发生这种情况.

It's been 2 days already that I am trying to understand why is this happening, however I do not have enough debugging skills to understand why is this occurring.

我需要使用 sql :: ConnectOptionsMap ，这样我才能传递所需的连接选项，例如字符集等.

I need to use the sql::ConnectOptionsMap so I can pass my desired connection options such as charset, etc.

一个简单的例子:

sql::ConnectOptionsMap connection_properties;

connection_properties["hostName"] = sql::SQLString("localhost");
connection_properties["userName"] = sql::SQLString("username");
connection_properties["password"] = sql::SQLString("password");
connection_properties["CLIENT_MULTI_STATEMENTS"] = (true);

sql::Driver * driver = get_driver_instance();
std::unique_ptr<sql::Connection> con(driver->connect(connection_properties));

在调试下与VS 2017一起编译:

Compiled with VS 2017, under debug:

Exception thrown at 0x00007FFFECC811D0 (vcruntime140d.dll) in Demo.exe: 0xC0000005: Access violation reading location 0xFFFFFFFFFFFFFFFF.

创建了一些小型转储"之后，我可以看到代码在这里崩溃了:

After creating some "mini dumps", I can see the code is crashing here:

    _NODISCARD static _CONSTEXPR17 int compare(_In_reads_(_Count) const char * const _First1,
        _In_reads_(_Count) const char * const _First2, const size_t _Count) noexcept // strengthened
        {   // compare [_First1, _First1 + _Count) with [_First2, ...)
#if _HAS_CXX17
        return (__builtin_memcmp(_First1, _First2, _Count));
#else /* _HAS_CXX17 */
        return (_CSTD memcmp(_First1, _First2, _Count)); <-- HERE
#endif /* _HAS_CXX17 */
        }

之前有人遇到过吗?我进行了很多搜索，直到现在找不到任何有此问题的人.

Has anyone encountered this before ? I have searched a lot, and could not find anyone having this issue until now.

我真的不明白为什么会这样，因为没有自定义，仅是文档中的一个示例...

I really cannot understand why this is happening, since there is nothing custom, just an example from the docs...

请告知.

推荐答案

我终于找到了这个问题的答案，这个问题在任何地方都没有记录.您可以使用"sql :: ConnectOptionsMap connection_properties;" 仅当您静态链接时. (mysqlcppconn-static.lib)

I found finally the answer to this problem, which is not documented anywhere. You can use "sql::ConnectOptionsMap connection_properties;" ONLY if you are statically linking the library. (mysqlcppconn-static.lib)

我是怎么发现的?遵循以下令人惊奇的信息: http://www.voidcn.com/article/p-yltwwlte-pd.html

How I found this out ? Following this amazing information from: http://www.voidcn.com/article/p-yltwwlte-pd.html

报价:

接口中使用的字符串均为SQLString.虽然这是一个 std :: string的进一步包装，无法传递std :: string 对象作为参数.由于它是一种动态链接方式，因此 DLL中的内存管理与EXE无关.通过 过去的对象将导致异常:bad_alloc

The strings used in the interface are all SQLString. Although it is a further wrapper of std::string, it is impossible to pass a std::string object as a parameter. Because it is a way of dynamic linking, the memory management in the DLL has no connection with the EXE. Passing the object in the past will cause an exception: bad_alloc

但是我确实测试了本文中的代码并将其添加到mysql_connection.cpp中，该错误消失了，但仍然无法正常工作.

I did however test the code from the article and added into the mysql_connection.cpp, and the error is gone but it will still not work.

我的警告:

我正在构建自己的mysql-connector-cpp-master的调试"版本，由于某种原因，编译未达到预期的效果".例如，在我的编译中，"mysqlcppconn-static.lib"不能编译为Debug，只能编译为"RelWithDebInfo"，只有10 MB，而正式"编译为64 MB.

I was building my own "Debug" version of the mysql-connector-cpp-master, and for some reason the compilation is not "as expected". For example in my compilation the "mysqlcppconn-static.lib" cannot be compiled as Debug, only "RelWithDebInfo" and is only 10 MB, whilst the "official" one is 64 MB.

结论:

您必须从MySQL网站静态链接发布版本(mysqlcppconn-static.lib)，才能使用"sql :: ConnectOptionsMap".我真的希望他们能醒来，并为人们和文档制作适当的库.

You must statically link the Release version (mysqlcppconn-static.lib) from the MySQL website in order to use "sql::ConnectOptionsMap". I really hope they will wake up and make a proper lib for people and documentation as well.

如果我能找到在Debug模式下构建它的方法，我将发布更新.

If I can find a way to build this in Debug mode, I shall post an update.

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