如何使用Boost.Log跨DLL边界？ [英] How can I use Boost.Log across DLL boundaries?

问题描述

我尝试整合 Boost.Log 在一个相当大的应用程序中，该应用程序由从DLL动态加载插件的主应用程序组成。最初的想法是传递日志源到插件，以便他们可以添加日志消息。但是，只要DLL中的代码尝试将消息记录到提供的源，应用程序就会崩溃，并出现访问冲突。

I am trying to integrate Boost.Log in a fairly large application that is composed of a main application that dynamically loads plugins from DLLs. The initial idea was to pass a logging source to plugins so that they can add log messages. However, as soon as code from a DLL tries to log a message to the provided source, the application crashes with an access violation.

以下最小示例说明了此问题：

The following minimal example illustrates the problem:

int main(int argc, char* argv[])
{
    boost::log::sources::severity_logger_mt<boost::log::trivial::severity_level> logger;

    // This is okay
    BOOST_LOG_SEV(logger, boost::log::trivial::info) << "From main()";

    // This crashes
    logFromDll(logger);

    return 0;
}

其中 logFromDll 在单独的（DLL）项目中定义：

Where logFromDll is defined in a separate (DLL) project:

Dll.cpp

TESTDLL_API void logFromDll(boost::log::sources::severity_logger_mt<boost::log::trivial::severity_level> &logger)
{
    BOOST_LOG_SEV(logger, boost::log::trivial::info) << "From dll";
}

如上所述，此操作在 logFromDll （使用visual studio 2010编译）。

As stated above, this crashes with an access violation in logFromDll (compiled with visual studio 2010).

.Log提供了一种机制，可用于全局存储：

Boost.Log provides a mechanism for "global storage" of logging sources:

声明一个全局日志记录器后，可以肯定有一个线程安全的
从应用程序代码的任何位置访问此记录器实例。
库还保证全局记录器实例将
独特，甚至跨模块边界。

Having declared a global logger, one can be sure to have a thread-safe access to this logger instance from any place of the application code. The library also guarantees that a global logger instance will be unique even across module boundaries.

像我需要的。因此，我设置了以下示例：

Sounds exactly like what I need. So I set up the following example:

Logger.h

BOOST_LOG_INLINE_GLOBAL_LOGGER_DEFAULT(my_logger, boost::log::sources::severity_logger_mt<boost::log::trivial::severity_level>)

Main.cpp

int main(int argc, char* argv[])
{
    boost::log::add_console_log
    (
        std::clog,
        boost::log::keywords::format = 
        (
            boost::log::expressions::stream << "[Custom format] " << boost::log::expressions::smessage  
        )
    );

    BOOST_LOG_SEV(my_logger::get(), boost::log::trivial::info) << "From main()";

    logFromDll();

    return 0;
}

Dll.cpp
$ b

Dll.cpp

TESTDLL_API void logFromDll()
{
    BOOST_LOG_SEV(my_logger::get(), boost::log::trivial::info) << "From dll";
}

这不会崩溃，但会产生以下输出：

This does not crash, but yields the following output:

[Custom format] From main() 
[2014-06-19 10:22:28.435366] [0x00000233] [info]    From dll

也就是说，我在main.cpp中设置的自定义格式化仅适用于我日志从主项目。任何来自DLL项目的日志记录都使用默认格式进行格式化。

That is, the custom formatting that I set up in main.cpp is only applied when I log from the main project. Any logging from the DLL project is formatted using the default format.

因此，如何以所有（格式化）选项设置的方式跨DLL边界执行日志记录在主项目中正确应用？

So, how can I perform logging across DLL boundaries in a way that all (formatting) options I set up in the main project are applied correctly?

推荐答案

我已经弄清楚了什么问题。 Boost.Log的文档声明：

I've figured out what the problem was. The documentation for Boost.Log states that:

如果您的应用程序包含多个模块 b $ b一个或多个dll的）使用Boost.Log，库必须被建立为
a共享对象。如果你有一个单一的可执行文件或单个模块
使用Boost.Log，您可以将库构建为静态
库。

If your application consists of more than one module (e.g. an exe and one or several dll's) that use Boost.Log, the library must be built as a shared object. If you have a single executable or a single module that works with Boost.Log, you may build the library as a static library.

我使用Boost.Log作为静态库。通过共享链接建立提升，并在我的项目中使用它解决了这个问题。

I was using Boost.Log as a static library. Building boost with shared linkage and using that in my project resolved the problem.

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