Re: Bug in gcc: assignment to non-lvalue

["Jonathan Wakely" <jwakely dot gcc at gmail dot com>]

On 24/09/2007, Jonathan Adamczewski <jadamcze@utas.edu.au> wrote:
>
> What about something like the following?
>
> struct proxy {
>     T& t;
>     proxy(T& t_) : t(t_) {}
>     proxy& operator=(const T& r) { foo(t, r); return *this; }
> };
>
> struct B { proxy get() { return proxy(bar); } };
>
> int main ()
> {
>     B b;
>     b.get() = 0;
> }

That is legal, 3.10 paragraph 10 says:
   An lvalue for an object is necessary in order to modify the object
except that an rvalue of class type can also be used to modify its
referent under certain circumstances. [Example: a member function
called for an object (9.3) can modify the object. ]

The example I posted doesn't use any member functions, but it's not
clear what other circumstances allow it.  I'm pretty sure assigning to
rvalues of builtin type shouldn't compile though.

Jon