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C++ Driver

Contribution Guidelines

On this page

  • Code Style
  • Commit Messages
  • Lifecycle Methods
  • Headers
  • Class Declarations
  • Inlines
  • Relational Operators

When contributing code, in addition to following the C++ Core Guidelines, please follow the same design guidelines and style guidelines as mongodb/mongo. Additions and exceptions are listed below. For anything that isn't explicitly covered here, default to the Google C++ Style Guide. Running clang-format with our configuration file, mongo-cxx-driver/.clang-format, will help ensure your code conforms to the above standards.

If a pull-request addresses a JIRA ticket, for a single-commit PR, prefix the subject line with the ticket ID. (For a multi-commit PR, we will add the ID later when we squash or merge it.)

CXX-883 Add commit message conventions to CONTRIBUTING.md

Capitalize subject lines and don't use a trailing period. Keep the subject at most 70 characters long. Use active voice! Imagine this preamble to get your phrasing right:

If applied, this commit will... [your subject line]

See Chris Beams' How to write a git commit message for more good guidelines to follow.

  • default-or-argument-bearing 'user' constructors

  • declaration-or-deletion-of-copy-constructor

  • declaration-or-deletion-of-move-constructor

  • declaration-or-deletion-of-copy-assignment-operator

  • declaration-or-deletion-of-move-assignment-operator

  • declaration-of-dtor

Public headers must have a ".hpp" suffix. Private headers must have a ".hh" suffix.

General structure:

  • License

  • Include Guard (#pragma once)

  • Header Prelude

  • System Headers <vector> (alphabetical order)

  • Driver Headers <path/to/header.hpp> (alphabetical order)

  • Open Namespace mongocxx

  • inline namespace v_noabi {

  • Code

  • } // namespace v_noabi

  • Close Namespace mongocxx

  • Header Postlude

Example:

// Copyright 2018-present MongoDB Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#pragma once
#include <driver/config/prelude.hpp>
#include <vector>
#include <driver/blah.hpp>
namespace mongocxx {
inline namespace v_noabi {
// Declarations
// Inline Implementations
} // namespace v_noabi
} // namespace mongocxx
#include <driver/config/postlude.hpp>

Guidelines:

  • Blank line at beginning and end of class declaration

  • Public section up top / private at bottom

  • Lifecycle methods first (see rules above)

  • Private Member Ordering

    • Friendships

    • Private Constructors

    • Private Methods

    • Private Variables

Example:

class foo {
public:
foo();
foo(foo&& other) noexcept;
foo& operator=(foo&& other) noexcept;
~foo();
private:
friend baz;
class MONGOCXX_PRIVATE impl;
std::unique_ptr<impl> _impl;
};
  • Define outside of class declaration

  • Specify inline keyword in declaration and definition (for clarity)

  • Prefer to use free functions

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