Why Does Visual Studio Compile Non-Constant References to Temporaries While Other Compilers Don't?

Non-Constant Reference Bound to Temporary: Visual Studio Anomaly

This issue arises when compiling code that attempts to bind a non-constant reference to a temporary object. While Visual Studio allows such code to compile, other compilers, like gcc, identify it as a compilation error.

Explanation

In the example provided:

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

The code attempts to bind a non-constant reference (Zebra &x) to a temporary object returned by the function goo(). According to the C standard, this should result in a compile error.

Visual Studio Extension

However, Visual Studio has an old extension that allows for this behavior. This extension essentially treats references to temporary objects as if they were references to non-temporary objects.

This extension was introduced to support legacy code bases. However, it can lead to unexpected behavior and is generally not recommended.

Recommended Approach

To avoid these anomalies, it is best to disable the extension using the /Za compiler flag. This will ensure that the code adheres to the C standard and will be consistently treated by different compilers.

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