CPP_STYLE_GUIDE.md

C++ Style Guide

Unfortunately, the C++ linter (based on Google’s cpplint), which can be run explicitly via make lint-cpp, does not currently catch a lot of rules that are specific to the Node.js C++ code base. This document explains the most common of these rules:

Left-leaning (C++ style) asterisks for pointer declarations

char* buffer; instead of char *buffer;

2 spaces of indentation for blocks or bodies of conditionals

if (foo)
  bar();

or

if (foo) {
  bar();
  baz();
}

Braces are optional if the statement body only has one line.

namespaces receive no indentation on their own.

4 spaces of indentation for statement continuations

VeryLongTypeName very_long_result = SomeValueWithAVeryLongName +
    SomeOtherValueWithAVeryLongName;

Operators are before the line break in these cases.

Align function arguments vertically

void FunctionWithAVeryLongName(int parameter_with_a_very_long_name,
                               double other_parameter_with_a_very_long_name,
                               ...);

If that doesn’t work, break after the ( and use 4 spaces of indentation:

void FunctionWithAReallyReallyReallyLongNameSeriouslyStopIt(
    int okay_there_is_no_space_left_in_the_previous_line,
    ...);

Initialization lists

Long initialization lists are formatted like this:

HandleWrap::HandleWrap(Environment* env,
                       Local<Object> object,
                       uv_handle_t* handle,
                       AsyncWrap::ProviderType provider)
    : AsyncWrap(env, object, provider),
      state_(kInitialized),
      handle_(handle) {

CamelCase for methods, functions and classes

Exceptions are simple getters/setters, which are named property_name() and set_property_name(), respectively.

class FooBar {
 public:
  void DoSomething();
  static void DoSomethingButItsStaticInstead();

  void set_foo_flag(int flag_value);
  int foo_flag() const;  // Use const-correctness whenever possible.
};

snake_case for local variables and parameters

int FunctionThatDoesSomething(const char* important_string) {
  const char* pointer_into_string = important_string;
}

snake_case_ for private class fields

class Foo {
 private:
  int counter_ = 0;
};

Space after template

template <typename T>
class FancyContainer {
 ...
}

Type casting

• Always avoid C-style casts ((type)value)
• dynamic_cast does not work because RTTI is not enabled
• Use static_cast for casting whenever it works
• reinterpret_cast is okay if static_cast is not appropriate

Memory allocation

• Malloc(), Calloc(), etc. from util.h abort in Out-of-Memory situations
• UncheckedMalloc(), etc. return nullptr in OOM situations

nullptr instead of NULL or 0

What it says in the title.

Do not include *.h if *-inl.h has already been included

Do

#include "util-inl.h"  // already includes util.h

instead of

#include "util.h"
#include "util-inl.h"

Avoid throwing JavaScript errors in nested C++ methods

If you need to throw JavaScript errors from a C++ binding method, try to do it at the top level and not inside of nested calls.

A lot of code inside Node.js is written so that typechecking etc. is performed in JavaScript.

Using C++ throw is not allowed.