问题描述
当我导入我构建的模块时，我得到这个与boost-python相关的错误：
When I import a module I built, I get this boost-python related error:
Traceback (most recent call last):
File "<string>", line 1, in <module>
ImportError: dlopen(./myMod.so, 2): Symbol not found: __ZN5boost6python7objects15function_objectERKNS1_11py_functionERKSt4pairIPKNS0_6detail7keywordES9_E
Referenced from: ./myMod.so
Expected in: flat namespace
in ./myMod.so
这实际意味着什么？为什么会出现这个错误？
What does this actually mean? Why was this error raised?
推荐答案
描述
问题是混合使用 libc ++ 编译的对象和使用 libstdc ++编译的对象 。
在我们的例子中，库 myMod.so （使用 <$编译） c $ c> libstdc ++ ）需要使用 libstdc ++ boost-python c $ c> （ boost-python-libstdc ++ 从现在开始）。当 boost-python 是 boost-python-libstdc ++ 时，它会正常工作。否则 - 在计算机上，其 boost-python 已使用 libc ++ （或其他c ++）编译库），加载和运行它会有问题。
In our case, the library myMod.so (compiled with libstdc++) need boost-python that compiled with libstdc++ (boost-python-libstdc++ from now). When boost-python is boost-python-libstdc++, it will work fine. Otherwise - on computer that its boost-python has compiled with libc++ (or another c++ library), it will have a problem loading and running it.
在我们的例子中，它发生是因为 libc ++ 开发人员故意改名称所有符号都阻止你（并保存你）混合来自他们库的代码和来自不同代码的代码： myMod.so 需要一个从类型。在 libc ++ 中，此类型的名称为 std :: __ 1 :: pair 。因此，找不到此符号。
In our case, it happens because that libc++ developers intentionally changed the name of all of their symbols to prevent you (and save you) from mixing code from their library and code from a different one: myMod.so need a function that take an argument from the type. In libc++, this type's name is std::__1::pair. Therefore, this symbol was not found.
要理解为什么混合两个版本的相同API是坏的，请考虑以下情况：有两个库： Foo 和 Bar 。它们都有一个函数，它接受 std :: string 并将它用于某些东西，但它们使用不同的c ++库。当 Foo 创建的 std :: string 将传递给 Bar ， Bar 会认为这是其c ++库的 std :: string 的一个实例，然后会发生不好的事情（它们是完全不同的对象）。
To understand why mixing two version of the same API is bad, consider this situation: There are two libraries: Foo and Bar. They both have a function that takes a std::string and uses it for something but they use a different c++ library. When a std::string that has been created by Foo will be passed to Bar, Bar will think that this is an instance of its c++ library's std::string and then bad things can happen (they are a completely different objects).
注意：在某些情况下，两个或两个都没有问题在程序的完全不同的部分中，相同API的更多不同版本。如果他们将在它们之间传递此API的对象，则会出现问题。但是，检查可能非常困难，特别是如果它们仅将API对象作为另一个对象的成员传递。此外，库的初始化函数可以执行不应发生两次的事情。另一个版本可能会再次执行这些操作。
Note: In some cases, there would be no problem with two or more different versions of the same API in a completely different parts of a program. There will be a problem if they will pass this API's objects between them. However, checking that can be very hard, especially if they pass the API object only as a member of another object. Also, a library's initialization function can do things that should not happen twice. Another version may do these things again.
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您始终可以重新编译库并使它们相互匹配。
You can always recompile your libraries and make them match each other.
您可以将 boost-python 链接到您的库作为静态库。然后，它几乎可以在每台计算机上运行（即使是没有安装 boost-python 的计算机）。查看更多相关信息。
You can link boost-python to your library as a static library. Then, it will work on almost every computer (even one that doesn't has boost-python installed). See more about that here.
myMod.so 需要另一个版本的 boost-python ，一个用特定的c ++库编译的版本。因此，它不适用于任何其他版本。
myMod.so need another version of boost-python, one that compiled with a specific c++ library. Therefore, It would not work with any another version.
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