非常量引用绑定到临时的 Visual Studio 错误?

2022-01-30 00:00:00 visual-studio c++ temporary-objects

我在 gcc 中编译一些可移植代码时遇到了这个问题.基本上这个奇怪的代码在 Visual Studio 中编译，这真的让我大吃一惊:

I ran into this while compiling some portable code in gcc. Basically this strange code compiles in Visual studio which really just blows my mind:

class Zebra {int x;};
Zebra goo() {Zebra z; return z;}
void foo(Zebra &x)
{
    Zebra y;
    x = y;
    foo(goo());
}

Visual Studio 让这个飞起来.gcc 会将此作为编译错误捕获.有趣的是，如果你将 Zebra 类型定义为 int，VC++ 会报错.相当矛盾的行为.想法?

Visual studio lets this one fly. gcc will catch this as a compile error. Interestingly, If you typedef Zebra to int, VC++ will complain. Quite contradictory behavior. Thoughts?

推荐答案

这是 Visual Studio 的旧扩展，我可以在 Microsoft 网站上找到的唯一参考是这个错误报告:临时对象可以绑定到非常量引用，它有以下示例代码:

This is old extension to Visual Studio, the only reference I could find on the Microsoft site was this bug report: Temporary Objects Can be Bound to Non-Const References, which has the following example code:

struct A {};

A     f1();
void f2(A&);

int main()
{
    f2(f1()); // This line SHALL trigger an error, but it can be compiled without any     errors or warnings.
}

回复说明之一:

有一个 4 级警告(如果您将/W4 传递给编译器，则启用 4 级警告)

There is a level 4 warning (level 4 warning are enabled if you pass /W4 to the compiler) for it

这篇博文:Visual C++ 是如此的自由，其中涵盖了这个扩展说明:

This blog post: Visual C++ is so Liberal which covers this extension notes that:

使用禁用语言扩展 (/Za) 会导致错误:

Using Disable Language Extensions (/Za) makes it an error:

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