Address of a cast expression in C++

[Matt Austern <austern@apple.com>]

With both 3.1 and TOT, the following program is rejected by
the C front end but accepted by the C++ front end.  g++
compiles it without error or warning.
     #include <stdio.h>

     int main() {
       int n = 0;
       char* p = &(char)n;
      *p = 0x7f;
       printf("%x\n", n);
     }

As I read the C++ Standard, this is incorrect; a diagnostic is
required.  5.4/1 says that the result of (char)n is an rvalue,
and 5.3.1/2 says that you can't take the address of an rvalue.

Question: is this violation of the C++ Standard deliberate,
or is it a bug?

The reason I ask, of course, is that gcc has a generalized
lvalue extension.  The manual says that even with this
extension it's illegal to write &(int)f.  Who's wrong: the manual,
or the compiler?

			--Matt