Created attachment 32419 [details]
Source file to reproduce the issue

If you compile the following piece of code using g++ (4.7.2):
"
class class1; 

namespace ns1 { 

class class2; 
class class3; 
}

ns1::class3 *func(ns1::class2 * cfg, const class1 * def); 

namespace ns1 { 

class class4 { 
#ifdef WORKAROUND
friend ns1::class3 *(::func)(ns1::class2 * cfg, const class1 * def);
#else
friend class3 *(::func)(class2 * cfg, const class1 * def); 
#endif
}; 
}
" (also attached)
you get the following:
$ g++ -c test.cpp
test.cpp:17:25: error: ‘func’ is neither function nor member function; cannot be declared friend
test.cpp:17:23: error: expected ‘;’ at end of member declaration
test.cpp:17:32: error: expected ‘)’ before ‘*’ token

Now, if you explicitely add the namespaces as they appear in the initial declaration (add -DWORKAROUND), the compilation succeeds.