G++, new types may not be defined in a return type

The error new types may not be defined in a return type

can be caused by forgetting a semicolon on the end of the declaration of a class.

错误的写法：

foo.h:

class Foo
{
// stuff
} // missing semicolon

foo.cc:

#include "foo.h"
Foo::Foo(int x) // error shows up in this line
{
// stuff
}

正确的写法：

foo.h:

class Foo
{
// stuff
}; // yay, semicolon!

foo.cc:

#include "foo.h"
Foo::Foo(int x)
{
// stuff
}