静态库被编译到客户机中。在编译时使用.lib，库的内容成为消费可执行文件的一部分。

动态库在运行时加载，而不是编译到客户端可执行文件中。动态库更加灵活，因为多个客户端可执行文件可以加载一个DLL并利用它的功能。这也将客户端代码的总体大小和可维护性保持在最小。

其他人已经充分解释了静态库是什么，但我想指出一些使用静态库的注意事项，至少在Windows上:

Singletons: If something needs to be global/static and unique, be very careful about putting it in a static library. If multiple DLLs are linked against that static library they will each get their own copy of the singleton. However, if your application is a single EXE with no custom DLLs, this may not be a problem. Unreferenced code removal: When you link against a static library, only the parts of the static library that are referenced by your DLL/EXE will get linked into your DLL/EXE. For example, if mylib.lib contains a.obj and b.obj and your DLL/EXE only references functions or variables from a.obj, the entirety of b.obj will get discarded by the linker. If b.obj contains global/static objects, their constructors and destructors will not get executed. If those constructors/destructors have side effects, you may be disappointed by their absence. Likewise, if the static library contains special entrypoints you may need to take care that they are actually included. An example of this in embedded programming (okay, not Windows) would be an interrupt handler that is marked as being at a specific address. You also need to mark the interrupt handler as an entrypoint to make sure it doesn't get discarded. Another consequence of this is that a static library may contain object files that are completely unusable due to unresolved references, but it won't cause a linker error until you reference a function or variable from those object files. This may happen long after the library is written. Debug symbols: You may want a separate PDB for each static library, or you may want the debug symbols to be placed in the object files so that they get rolled into the PDB for the DLL/EXE. The Visual C++ documentation explains the necessary options. RTTI: You may end up with multiple type_info objects for the same class if you link a single static library into multiple DLLs. If your program assumes that type_info is "singleton" data and uses &typeid() or type_info::before(), you may get undesirable and surprising results.

如果您的库将在几个可执行文件之间共享，那么将其动态化以减少可执行文件的大小通常是有意义的。否则，一定要让它是静态的。

使用dll有几个缺点。装载和卸载它有额外的开销。还有一个额外的依赖关系。如果您更改dll使其与执行表不兼容，则它们将停止工作。另一方面，如果您更改了静态库，则使用旧版本编译的可执行文件将不会受到影响。

如果库是静态的，则在链接时将代码链接到可执行文件中。这使您的可执行文件更大(如果您走动态路线)。

如果库是动态的，那么在链接时，对所需方法的引用将内置于可执行文件中。这意味着您必须发布可执行文件和动态库。您还应该考虑对库中代码的共享访问是否安全、首选加载地址以及其他事项。

如果你能接受静态库，那就使用静态库。

静态库增加了二进制文件中代码的大小。它们总是被加载，无论你用什么版本的代码编译，都是将运行的代码版本。

动态库的存储和版本是分开的。如果更新被认为与原始版本二进制兼容，则有可能加载的动态库版本不是随代码附带的原始版本。

此外，动态库不一定被加载——它们通常在第一次调用时被加载——并且可以在使用相同库的组件之间共享(多个数据加载，一个代码加载)。

动态库在大多数时候被认为是更好的方法，但最初它们有一个重大缺陷(谷歌DLL地狱)，这个缺陷几乎被最近的Windows操作系统(特别是Windows XP)所消除。

Ulrich Drepper关于“如何编写共享库”的论文也是一个很好的资源，详细介绍了如何最好地利用共享库，或者他所说的“动态共享对象”(DSOs)。本文主要讨论ELF二进制格式的共享库，但有些讨论也适用于Windows dll。