What is the difference between static and shared libraries?
我使用 Eclipse 并且有几种项目类型，包括静态库和共享库?一个比另一个有优势吗?
I use Eclipse and there are several project types including Static Libraries and Shared Libraries? Does one have an advantage over the other?
共享库是 .so(或在 Windows .dll 中，或在 OS X .dylib 中)文件.与库相关的所有代码都在这个文件中，并且在运行时被使用它的程序引用.使用共享库的程序只引用它在共享库中使用的代码.
Shared libraries are .so (or in Windows .dll, or in OS X .dylib) files. All the code relating to the library is in this file, and it is referenced by programs using it at run-time. A program using a shared library only makes reference to the code that it uses in the shared library.
静态库是 .a(或在 Windows 中的 .lib)文件.与库相关的所有代码都在这个文件中，并且在编译时直接链接到程序中.使用静态库的程序从静态库中复制它使用的代码，并使其成为程序的一部分.[Windows 也有用于引用 .dll 文件的 .lib 文件，但它们的作用与第一个相同].
Static libraries are .a (or in Windows .lib) files. All the code relating to the library is in this file, and it is directly linked into the program at compile time. A program using a static library takes copies of the code that it uses from the static library and makes it part of the program. [Windows also has .lib files which are used to reference .dll files, but they act the same way as the first one].
There are advantages and disadvantages in each method:
Shared libraries reduce the amount of code that is duplicated in each program that makes use of the library, keeping the binaries small. It also allows you to replace the shared object with one that is functionally equivalent, but may have added performance benefits without needing to recompile the program that makes use of it. Shared libraries will, however have a small additional cost for the execution of the functions as well as a run-time loading cost as all the symbols in the library need to be connected to the things they use. Additionally, shared libraries can be loaded into an application at run-time, which is the general mechanism for implementing binary plug-in systems.
Static libraries increase the overall size of the binary, but it means that you don't need to carry along a copy of the library that is being used. As the code is connected at compile time there are not any additional run-time loading costs. The code is simply there.
就个人而言，我更喜欢共享库，但在需要确保二进制文件没有很多可能难以满足的外部依赖项时使用静态库，例如特定版本的 C++ 标准库或特定版本的 Boost C++图书馆.
Personally, I prefer shared libraries, but use static libraries when needing to ensure that the binary does not have many external dependencies that may be difficult to meet, such as specific versions of the C++ standard library or specific versions of the Boost C++ library.