C ++：警告：C4930：未调用原型函数（是否要使用变量定义？） [英] C++: warning: C4930: prototyped function not called (was a variable definition intended?)

问题描述

我有一个没有默认构造函数的类，我创建了一个变量而没有错误给出参数，但是我遇到了一个链接器错误，而不是一个不错的编译器错误，我无法

I have a class that does not have a default constructor, I created a variable without giving parameters by mistake, but instead of a nice compiler error, I got a linker error, where I couldn't find the line of code that was causing it.

最后，我设法找到了导致该问题的代码，直到那时我才注意到警告：

In the end, I managed to find the code that caused this, and only then I noticed that I was getting this warning:

C++: warning: C4930: prototyped function not called (was a variable definition intended?)

当我从以下位置更改代码时，很奇怪：

What's weird is when I changed the code from:

MyClass foo();

到

MyClass foo;

我确实遇到了编译器错误。

I did get a compiler error.

有人可以向我解释为什么编译器突然开始表现奇怪，是bug还是什么？

Can someone explain to me why the compiler suddenly started acting strange, is it a bug or something?

推荐答案

此

MyClass foo();

是具有返回类型MyClass且不接受参数的函数声明。

is a function declaration that has return type MyClass and does not accept arguments..

This

MyClass foo;

是对象定义。由于您的类MyClass没有默认的构造函数，因此编译器会发出错误。

is an object definition. As your class MyClass has no the default constructor the compiler issues an error.

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