C ++代码在缺少标头的情况下运行，为什么? [英] C++ code runs with missing header, why?

问题描述

我刚刚意识到我应该为 abs()函数包含 abs()所需的#include< cstdlib>

I just realized that I am supposed to include the #include<cstdlib> required by abs() for the abs() function.

 #include<iostream>
    using namespace std;
    int main()
    {
        int result;
        result = abs(-10);
        cout << result << "\n";
        return 0;

    }

即使我忘记了重要的标头(#include< cstdlib> )，为什么此代码仍然可以工作?

Why does this code still work, even though I forgot the important header (#include<cstdlib>)?

推荐答案

这是因为 iostream 间接包含了 abs()的定义.标准允许，但不应依赖它，因为它取决于实现(即，您的代码可能无法在其他某些编译器上编译).

That's because iostream indirectly includes definition for abs(). It is allowed by the Standard, but should not be relied upon, because it's implementation-dependant (i.e. your code may not compile on some other compilers).

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