最令人头疼的解析错误:没有参数的构造函数 [英] A most vexing parse error: constructor with no arguments

问题描述

我正在使用g ++在Cygwin中编译C ++程序，并且我有一个其构造函数没有参数的类.我有台词:

I was compiling a C++ program in Cygwin using g++ and I had a class whose constructor had no arguments. I had the lines:

MyClass myObj();
myObj.function1();

当尝试对其进行编译时，我收到消息:

And when trying to compile it, I got the message:

error: request for member 'function1' in 'myObj', which is of non-class type 'MyClass ()()'

经过一番研究，我发现解决方法是将第一行更改为

After a little research, I found that the fix was to change that first line to

MyClass myObj;

我可以发誓我以前在C ++中用括号完成了空的构造函数声明.这可能是我正在使用的编译器的限制吗?还是语言标准真的说不对没有参数的构造函数使用括号?

I could swear I've done empty constructor declarations with parentheses in C++ before. Is this probably a limitation of the compiler I'm using or does the language standard really say don't use parentheses for a constructor without arguments?

推荐答案

尽管 MyClass myObj(); 可以被解析为带有空初始化程序或函数声明的对象定义，语言标准指定该声明为始终可以通过函数声明解决歧义.在其他情况下，例如，允许使用空括号初始化程序.在 new 表达式中，或构造一个 value-initialized 临时文件.

Although MyClass myObj(); could be parsed as an object definition with an empty initializer or a function declaration the language standard specifies that the ambiguity is always resolved in favour of the function declaration. An empty parentheses initializer is allowed in other contexts e.g. in a new expression or constructing a value-initialized temporary.

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