当同一个命名空间中有两个具有相同签名的函数时会发生什么？

Question

As far as I understand, I can use namespaces to avoid functions overriding each other. But what if the namespaces have the same names?

I included both of the .h files below, called VideoLibrary::check() and it compiles. Why? Doesn't it contradict the purpose of namespace?

file1.h and file2.h:

namespace VideoLibrary
{
  void check();
}

file1.cpp:

namespace VideoLibrary
{
  void check()
    {
        printf("check1");
    }
}

file2.cpp:

namespace VideoLibrary
{
  void check()
    {
        printf("check2");
    }
}

I'm concerned mostly because my project includes external libraries, and i'm worrying it includes functions with the same signature as in my project. How can I get any error for such a case in compilation time? I'm using Xcode as an editor if it matters.

Answer 1

如果您在不同的翻译单元中有 2 个（非内联）相同函数的定义，则您有 ODR（一个定义规则）违反 NDR（无诊断要求）。