Throwing an exception as const&

Question

Take the following code;

void DoThrow( const std::exception& e )
{
    throw e;
}

int main( int nArgs, char* args[] )
{
    std::exception e;
    try
    {
        DoThrow( e );
    }
    catch( std::exception& e )
    {
        // const exception ref is caught
    }


    return 0;
}

I'm trying to retrofit const correctness in my project and inadvertently created the above situation. As it stands, in Dev Studio the catch block DOES catch the exception, despite the fact that it is thrown as a const & but caught as a non-const &.

Question - Should it? :-)

Answer 1

throw takes an expression and creates via copy-initialization an exception object based on the static type of that expression. The exception object is not a const object.

The catch statement initializes a reference to the exception object, not the object (if any) referred to by the throw expression.

Answer 2

我不知道规范说的是什么，但在我看来，在实践中，使用RTTI将一个异常调度到正确的“catch”块（一些编译器合成代码必须这样做），“const”与之无关。