Background
C++ is the main development language used by many of Google's open-source projects. As
every C++ programmer knows, the language has many powerful features, but this power
brings with it complexity, which in turn can make code more bug-prone and harder to read and
maintain.
The goal of this guide is to manage this complexity by describing in detail the dos and don'ts of
writing C++ code. These rules exist to keep the code base manageable while still allowing
coders to use C++ language features productively.
Style, also known as readability, is what we call the conventions that govern our C++ code.
The term Style is a bit of a misnomer, since these conventions cover far more than just source
file formatting.
One way in which we keep the code base manageable is by enforcing consistency. It is very
important that any programmer be able to look at another's code and quickly understand it.
Maintaining a uniform style and following conventions means that we can more easily use
"pattern-matching" to infer what various symbols are and what invariants are true about them.
Creating common, required idioms and patterns makes code much easier to understand. In
some cases there might be good arguments for changing certain style rules, but we
nonetheless keep things as they are in order to preserve consistency.
Another issue this guide addresses is that of C++ feature bloat. C++ is a huge language with
many advanced features. In some cases we constrain, or even ban, use of certain features.
We do this to keep code simple and to avoid the various common errors and problems that
these features can cause. This guide lists these features and explains why their use is
restricted.
Open-source projects developed by Google conform to the requirements in this guide.
Note that this guide is not a C++ tutorial: we assume that the reader is familiar with the
language.
Header Files
In general, every .cc file should have an associated .h file. There are some common
exceptions, such as unittests and small .cc files containing just a main() function.
Correct use of header files can make a huge difference to the readability, size and
performance of your code.
