Is the book <<Thinking in C++>> Wrong?

[meili100]

An example in the book Thinking in C++:

class X{};

X f() {
	return X();
}

void g1(X&){}
void g2(const X&){}


int main(){

	g1(f());
	return 0;
}

According to the book the compiler should report error because f() returns a temporary object which is defined by the compiler as "const".
However I compile this code using VS 2005 it works. Is the book wrong?

Thanks!

[brewbuck]

The book is not wrong. The compiler is wrong.

[laserlight]

That is probably due to a too low warning level. I upped my warning level to /W4 and was informed:

warning C4239: nonstandard extension used : 'argument' : conversion from 'X' to 'X &'
        A non-const reference may only be bound to an lvalue

So what you see is nonstandard, and Thinking in C++ is correct.

[anon]

VC++ seems to be kind of lax with constness of temporaries. In the current project I had some function prototypes like

void foo(SomeObject&);

And I called them like this:

foo(SomeObject(x, y, x));

MingW however requires SomeObject to be const in the function prototype for this to work.