http://google-styleguide.googlecode.com ... pguide.xml
It is on googles coding style guide for C++, so you might thinks it has nothing of value in, but its got some gems you might wanna polish up on, for example.
Don't use an #include when a forward declaration would suffice.
When you include a header file you introduce a dependency that will cause your code to be recompiled whenever the header file changes. If your header file includes other header files, any change to those files will cause any code that includes your header to be recompiled. Therefore, we prefer to minimize includes, particularly includes of header files in other header files.
You can significantly reduce the number of header files you need to include in your own header files by using forward declarations. For example, if your header file uses the File class in ways that do not require access to the declaration of the File class, your header file can just forward declare class File; instead of having to #include "file/base/file.h".
How can we use a class Foo in a header file without access to its definition?
We can declare data members of type Foo* or Foo&.
We can declare (but not define) functions with arguments, and/or return values, of type Foo. (One exception is if an argument Foo or const Foo& has a non-explicit, one-argument constructor, in which case we need the full definition to support automatic type conversion.)
We can declare static data members of type Foo. This is because static data members are defined outside the class definition.
On the other hand, you must include the header file for Foo if your class subclasses Foo or has a data member of type Foo.
Sometimes it makes sense to have pointer (or better, scoped_ptr) members instead of object members. However, this complicates code readability and imposes a performance penalty, so avoid doing this transformation if the only purpose is to minimize includes in header files.
Of course, .cc files typically do require the definitions of the classes they use, and usually have to include several header files.
Note: If you use a symbol Foo in your source file, you should bring in a definition for Foo yourself, either via an #include or via a forward declaration. Do not depend on the symbol being brought in transitively via headers not directly included. One exception is if Foo is used in myfile.cc, it's ok to #include (or forward-declare) Foo in myfile.h, instead of myfile.cc.
