/Zc:referenceBinding (Enforce reference binding rules)

2021-08-03

When the /Zc:referenceBinding option is specified, the compiler doesn't allow a non-const lvalue reference to bind to a temporary.

Syntax

/Zc:referenceBinding[-]

Remarks

If /Zc:referenceBinding is specified, the compiler follows section 8.5.3 of the C++11 standard: It doesn't allow expressions that bind a user-defined type temporary to a non-const lvalue reference. By default, or if /Zc:referenceBinding- is specified, the compiler allows such expressions as a Microsoft extension, but a level 4 warning is issued. For code security, portability and conformance, we recommend you use /Zc:referenceBinding.

The /Zc:referenceBinding option is off by default. The /permissive- compiler option implicitly sets this option, but it can be overridden by using /Zc:referenceBinding-.

Example

This sample shows the Microsoft extension that allows a temporary of a user-defined type to be bound to a non-const lvalue reference.

// zcreferencebinding.cpp
struct S {
};

void f(S&) {
}

S g() {
    return S{};
}

int main() {
    S& s = g();         // warning C4239 at /W4
    const S& cs = g();  // okay, bound to const ref
    f(g());             // Extension: error C2664 only if /Zc:referenceBinding
}

For more information about conformance issues in Visual C++, see Nonstandard Behavior.

To set this compiler option in the Visual Studio development environment

Open the project's Property Pages dialog box. For details, see Set C++ compiler and build properties in Visual Studio.
Select the Configuration Properties > C/C++ > Command Line property page.
Modify the Additional Options property to include /Zc:referenceBinding and then choose OK.

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