GCC4.1 become strogner in regard of some C++ patterns.
One heavily used in Hotspot is
class Foo {
 void Foo::bar() {}
};

which should be written as
class Foo {
 void bar() {}
};

Also if some external inline function is declared as friend, its body is expected to be already seen.

 Generally looks like useful cleanup + support for next major GCC release.