两个静态库，两个不同的向量实现，链接器会做什么？ [英] Two static libs, two different vector implementations, what would the linker do?

问题描述

假设我们有两个用 std :: vector 的不同实现构建的静态库。这两个二进制文件都具有 push_back 和 pop_back 的代码（因为向量通常是头文件）。当我们试图在项目中使用这两个库时，链接器会做什么。它会给一个错误吗？链接器可以删除每个方法的一个实现，以便可以进行以下操作：

push_back 库调用 push_back 从第一个库执行

pop_back 从第一个库调用 pop_back 从第二个库执行

解决方案

它会给一个错误吗？取决于你如何定义错误。

这可能不会在链接时给你一个错误。但它肯定会损坏你的可执行文件。当遇到符号的多个定义时，链接器假定，它们是相同的，因此除了其中一个之外的所有其他都可以被丢弃。如果他们不相同，你违反了单一定义规则，这意味着你走向未定义的行为土地。任何事情都可能发生。很可能，您会看到随机崩溃。

Imagine that we have two static libraries built with different implementations of std::vector. Both of these binaries would have the code for both push_back and pop_back (since vector is usually header only). What would the linker do when we tried to use both of these libraries in a project. Would it give an error? Could the linker remove one implementation of each of these methods so that following is possible:

push_back call from the second library calls push_back implementation from the first library

pop_back call from the first library calls pop_back implementation from the second library

解决方案

Would it give an error? Depends on how you define "error".

It probably would not give you an error at link-time. But it would certainly corrupt your executable. The linker assumes, when it encounters multiple definitions of a symbol, that they are identical, and so all but one of them can be discarded. If they're not identical, you're violating the One-Definition Rule, which means you're heading into Undefined Behavior-land. Anything might happen. Most likely, you'll see random crashes.

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