[jv@smith misc]$ cat -n decl_friend_class.cpp
     1
     2  #ifdef DD
     3  class d;
     4  #endif
     5
     6  class c
     7  {
     8    friend class d;
     9    d* p;
    10  };
    11
[jv@smith misc]$ /usr/local/gcc/gcc-4.0.0/bin/g++ -c -W -Wall decl_friend_class.cpp
[jv@smith misc]$ /usr/local/gcc/gcc-4.0.1/bin/g++ -c -W -Wall decl_friend_class.cpp
decl_friend_class.cpp:9: error: ISO C++ forbids declaration of 'd' with no type
decl_friend_class.cpp:9: error: expected ';' before '*' token
[jv@smith misc]$ /usr/local/gcc/gcc-4.0.1/bin/g++ -c -W -Wall -fpermissive
decl_friend_class.cpp
decl_friend_class.cpp:9: warning: ISO C++ forbids declaration of 'd' with no type
decl_friend_class.cpp:9: error: expected ';' before '*' token
[jv@smith misc]$ /usr/local/gcc/gcc-4.0.1/bin/g++ -c -W -Wall -DDD
decl_friend_class.cpp
[jv@smith misc]$ icc -c -w2 decl_friend_class.cpp
[jv@smith misc]$

The icc here is icc 8.1

The original testcase comes from SystemC 2.0.1,
in include/systemc/kernel/sc_module_name.h

( http://www.systemc.org/ )

IANAC++LL.  It is not immediately clear to me from the
standard whether a friend class decl declares that class,
though the description of a friend function decl suggests
- to me, anyway - that it might.

I would be grateful if anyone could refer me to a discussion
of whether or not this is valid C++, acording to current
interpretations of the standard.

However:

I believe that this code is accepted by gcc-2.95, gcc-3.2.x, gcc-3.4.x,
gcc-4.0.0 without warning, so if it has been determined to be invalid,
it should reeceive a "deprecated" warning and/or require -fpermissive
before it ceases to be accepted by gcc.

Regards,

John.

I will test minor release candidates more in future...