Squashed 'third_party/allwpilib_2016/' changes from 7f61816..3ce6feb
3ce6feb Updated release number for the new release
e054bbc This adds StopMotor() to the SpeedController interface for C++ and Java. For Java, this is as simple as just adding it, as all motors already have an implementation from MotorSafety that is correctly resolved. For C++, I had to override StopMotor in the classes that descend from SafePWM and explicitly call the SafePWM version. RobotDrive now calls StopMotor on each of its SpeedControllers, instead of calling Disable or setting the motor to 0.0 as it was doing previously.
a15b9dc Merge "More updates to the Gyro test fixing potential null pointer exception"
21b7213 Added Config routine to allow enabling/disabling of limit switch and soft limits. This improves upon the ConfigLimitMode routine, which does not allow certain combinations of enable/disabled limit features. Also keeps parity with LV and Java.
1b45237 Merge "Add an additional member variable for "stopped" which indicates the CAN motor controller has been explicitly stopped, but not disabled by the user (main use case is MotorSafety tripping). When Set() is called the next time the controller will be re-enabled automatically."
1096b15 Add an additional member variable for "stopped" which indicates the CAN motor controller has been explicitly stopped, but not disabled by the user (main use case is MotorSafety tripping). When Set() is called the next time the controller will be re-enabled automatically.
7da21fa More updates to the Gyro test fixing potential null pointer exception
ede5862 Rate-limit duplicate error messages to avoid flooding console.
c22284d Merge "artf4818: Fix CAN Talon JNI references with underscores."
cac3741 Merge "Updated PDP port of Talon and disabled PDP tests for Victor and Jaguar since the Victor and Jaguar don't draw enough current for the PDP to read above 0. PDP tests for both java and cpp only test the Talon now."
097aa8c Fixed the gyro deviation over time test
1d647b3 artf4818: Fix CAN Talon JNI references with underscores.
368cfc7 Merge "Fixed the motor tests by reducing speed to within the limits of the encoders we use. Also fixed java pid tolerances since getAvgError() was broken. It is now fixed and works properly. Added tests for both java and cpp that test if pid tolerances are working using fake input output pairs."
833e459 Updated PDP port of Talon and disabled PDP tests for Victor and Jaguar since the Victor and Jaguar don't draw enough current for the PDP to read above 0. PDP tests for both java and cpp only test the Talon now.
6c096a3 Fixed the motor tests by reducing speed to within the limits of the encoders we use. Also fixed java pid tolerances since getAvgError() was broken. It is now fixed and works properly. Added tests for both java and cpp that test if pid tolerances are working using fake input output pairs.
dd7eb0f Fixed robot drive for C++ Simulation
258a622 Merge "Update version number for Release 3 Print distinctive message on robot program startup Change-Id: Ic91b81bd298ee6730503933cf0e733702e4b4405"
b1386c6 Update version number for Release 3 Print distinctive message on robot program startup Change-Id: Ic91b81bd298ee6730503933cf0e733702e4b4405
a58de40 Merge "Removed publishing of java sim jar"
792d0d3 PDP Classes should support any PDP address
35df955 Merge "Remove maven local as a possible search location"
a0ce9ee Another improvement to HAL-joy getting to ensure it works in future RIO image updates.
0f02c31 Removed publishing of java sim jar
8435ac7 DriverStation::GetJoystickName(): Make work for stick>0.
b4cf4f4 Remove maven local as a possible search location
c3000c3 Merge "Fix HALGetJoystickDescriptor()."
4dec0b4 Merge "Fixed Simulation C++ API"
abc9c27 Fixed Simulation C++ API
b8ae9ec Fix HALGetJoystickDescriptor().
a60f874 Artf4800: Fixes HALGetJoystick*** Segfault
010b584 Merge "fix sim_ds launch script"
4429e16 Merge "Added build dir specification for sim javadoc to not overwrite athena javadoc"
ec9349b Initialized the m_sensors variable to fix artf4798.
9745af8 Added build dir specification for sim javadoc to not overwrite athena javadoc
4da8702 fix sim_ds launch script
05acf79 Fix C++ PIDController SetToleranceBuffer and OnTarget locking.
94a6b05 Merge "Fix onTarget() so that it returns false until there are any values retrieved"
d06053d Fix onTarget() so that it returns false until there are any values retrieved
74927cc Correctly set smart dashboard type for AnalogGyro and ADXRS450_Gyro.
070752f Merge "Fixed sim_ds script library path"
21a8bab Merge "PIDController feed forward term can now be calculated by the end user"
56bd6da Fixed sim_ds script library path
07710f1 Merge "Fixing install script... again"
e1cb61f Use absolute path for NT persistent storage.
09c7482 Fixing install script... again
a3b8bec PIDController feed forward term can now be calculated by the end user
790adb0 artf2612: Update license in source files.
042671c Merge "Removed gz_msgs from wpilibcSim"
c111690 Ultrasonic: replace linked list with std::set.
d71a8ed Removed gz_msgs from wpilibcSim
37259f7 Merge "Replaced linked list in Notifier with std::list"
cd17e7a Merge "Renamed Gyro to AnalogGyro to match athena API"
c5c8a87 Replaced linked list in Notifier with std::list
89405d8 Renamed Gyro to AnalogGyro to match athena API
4a19490 Merge "Adds CANTalon to LiveWindow"
c4a3567 Merge "Fixing the frcsim installer script"
295648f Adds CANTalon to LiveWindow
1b964a2 Merge "Fixes CAN devices in C++ library not showing in the livewindow"
7ba5cee Merge "HAL: Use extern "C" in implementation files."
d17d242 Fixes CAN devices in C++ library not showing in the livewindow
25a771a Added linear digital filters
7349c2c Fixing the frcsim installer script
c82122c Merge "Default bufLength for PIDController in Java should be 1"
58f3f97 Merge "Adds WaitResult to Java waitForInterrupt"
bc8ed12 HAL: Use extern "C" in implementation files.
4cac89e Default bufLength for PIDController in Java should be 1
64fcdcc Keep track of FPGA time rollovers with 64-bit time.
d30b283 Merge "Change C++ Notifier to allow std::function callback."
6ee3052 Merge "Rewrite C++ Notifier to use HAL multi-notifier support."
f5d09e2 Merge "Rewrite Java Notifier and update Interrupt JNI."
d0274aa Merge "Readded styleguide accidentally removed in the reorg"
68311ad Merge "Artf4179: Allow alternate I2C addresses for ADXL345_I2C"
dee12d4 Readded styleguide accidentally removed in the reorg
fa100df Fixed some typos in the comments of MotorEncoderFixture.java, a method name in CANMotorEncoderFixture.java, and the README files
3397b5c Adds WaitResult to Java waitForInterrupt
5f0dffd Artf4177: Use read byte count for ReadString
8564f33 Artf4179: Allow alternate I2C addresses for ADXL345_I2C
e52b52d Change C++ Notifier to allow std::function callback.
40b29e7 Rewrite C++ Notifier to use HAL multi-notifier support.
d126f45 Rewrite Java Notifier and update Interrupt JNI.
557805a Merge "finishing up FRCSim installer"
911b64b finishing up FRCSim installer
e24fe6f Merge "Artf4776 Fixes First DIO PWM usage errors"
f8f9284 Merge "Artf4774 Fixes HAL getHALErrorMessage missing error"
84428d5 Merge "Prevent double free in DigitalGlitchFilter"
a00a5ff Merge "Set correct error message"
9aeee98 Prevent double free in DigitalGlitchFilter
5d2186c working on install process for FRCSim 2016
7fdb616 Merge "This commit adds documentation generation, including grabbing ntcore sources, for both Java and C++. This will need changes made in the wpilib promotion tasks to copy the generatd documentation to the correct places."
f67ebca Improved READMEs
8a7c019 Artf4776 Fixes First DIO PWM usage errors
1cd2f9a Added libnipalu to make vision programs link properly
375b92a This commit adds documentation generation, including grabbing ntcore sources, for both Java and C++. This will need changes made in the wpilib promotion tasks to copy the generatd documentation to the correct places.
8d0a990 Set correct error message
b65401f Artf4774 Fixes HAL getHALErrorMessage missing error
5f918be Condition java sim build on -PmakeSim flag
53bd180 Merge "Add SPARK and SD540 motor controllers"
66cbe69 Fixed double free of DriverStation.
431f345 Repaired simulation build on linux
611593c Add Cmake wrappers and unzip desktop ntcore builds
51a18cd Add SPARK and SD540 motor controllers
c05e883 Merge changes I55ce71c6,I803680c1
2b80029 Rewrite CANTalon JNI layer.
ef4c45b Last feature addition for CANTalon java/C++ user-facing API.
Change-Id: Ia3a124978a426991890b6f8abbe07d34d75ba38d
git-subtree-dir: third_party/allwpilib_2016
git-subtree-split: 3ce6feb8acdeca46e93a55280fb6ace3a4d5bcd6
diff --git a/styleguide/cppguide.html b/styleguide/cppguide.html
new file mode 100644
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+<!DOCTYPE html>
+<html>
+<head>
+<meta http-equiv="content-type" content="text/html; charset=UTF-8">
+<title>WPILib C++ Style Guide</title>
+<link rel="stylesheet" type="text/css" href="include/styleguide.css">
+<script language="javascript" src="include/styleguide.js"></script>
+</head>
+<body onload="initStyleGuide();">
+<div id="content">
+<h1>WPILib C++ Style Guide (Based on the <a href=http://google-styleguide.googlecode.com/svn/trunk/cppguide.html>Google C++ Style Guide</a>)</h1>
+<div class="horizontal_toc" id="tocDiv"></div>
+
+<div class="main_body">
+
+<h2 class="ignoreLink" id="Background">Background</h2>
+
+<p><strong>This guide is a work in progress.</strong>
+We are currently working on getting this guide updated to
+a point where it is useful for WPILib developers to use.</p>
+
+<p>C++ is one of the two main languages (Java being the other)
+used in WPILib; in order to maintain consistency and keep the
+maintenance of the code manageable, we use this style guide.</p>
+
+<p>There are two main overarching purposes to this guide. The first
+is to act as a normal C++ style guide (both in terms fo formatting
+and programming practices) for C++ developers of WPILib.
+The other purpose is to help Java programmers who may
+know a moderate amount of C++ but may not be fully
+up to date with things like C++11 and so may not even
+realize that certain C++ features exist.</p>
+
+<p>This style guide is a heavily modified version of the
+<a href=http://google-styleguide.googlecode.com/svn/trunk/cppguide.html>
+Google C++ Style Guide</a>. The Google Style Guide has
+a lot of good points and is a good read, but in order
+to cut the style guide down to a more readable size and to
+focus mroe on WPILib-specific information, we have
+altetered the original style guide in several ways.</p>
+
+<p>One way in which we <em>haven't</em> done much to
+alter the original style guide is to keep the vast
+majority of the formatting/naming/etc. related
+information intact. This is both so that we
+do not have to write up our own standards and so
+that existing tools such as clang-format and
+the Google eclipse format configuration files
+can work out of the box. All of these things
+should be relatively non-controversial and do not
+require much discussion.</p>
+
+<p>Where we deviate more from the original guide is
+in the style of the code itself. At the moment (ie,
+when we first created this modified version), we
+deleted all of the sections of the original guide
+which mandate particular programming practices
+such as forbidding exceptions, multiple inheritance,
+etc. However, as time goes on, we gradually add in more
+information along this lines, either by copying
+directly from Google's Style Guide or by writing
+our own decisions and best practices, some of which
+may be very WPILib-specific.</p>
+
+<p>As the original guide makes very clear, consistency
+is extremely important to keeping the code base
+manageable, and so we encourage that, wherever
+reasonable, that you keep everything consistent
+with whatever the standard style is.</p>
+
+<p>Along with just C++ style, it is also important
+to keep in mind that WPILib consists of both a C++
+and Java half. In order to keep things consistent
+and easier for users, we ask that, in general,
+Java and C++ be kept as consistent with one another
+as reasonable. This includes everything from using
+two spaces for indentation in both language to
+keeping the inheritance structure essentially the
+same in both. Although the two do not have to be
+precisely the same, it does mean that if there is
+something that you are doing which will be imposssible
+to reproduce in some way in Java, then you may
+want to reconsider.</p>
+
+<p>One final thing to remember is that High School
+students with relatively little experience programming
+are the main user for this code, and throwing the full
+brunt of C++ at a student just learning how to program
+is likely not the best of ideas. As such, any
+user-facing APIs should minimize the use of any
+more complicated C++ features. As always,
+use your judgement and ask others in cases where
+there is something which may violate anything
+in this guide.</p>
+
+<h2 id="Programming_Guidelines">Programming Guidelines</h2>
+<p>C++ is a large, complicated language, and in order
+to ensure that we stay consistent and maintain certain
+best practices, we have certain rules. For the most part
+these are common sense rules and in some cases exist
+solely to point out features of C++ that someone more
+familiar with Java may not realize even exist.</p>
+
+<h3 id="Pointers">Pointers</h3>
+<p>In general, we strongly discourage the use of
+raw pointers in C++ code; instead, references or
+STL pointers should be used where appropriate.
+There are two exceptions to this rule:</p>
+<ul>
+ <li>When interfacing with lower-level C code or
+ with any libraries which force you to use raw pointers.</li>
+ <li>In order to keep user interfaces consistent,
+ we may keep around deprecated functions which
+ take raw pointers. Any user-facing functions
+ which take raw pointers should be deprecated
+ using the
+ <a href=https://en.wikipedia.org/wiki/C%2B%2B14#The_attribute_.5B.5Bdeprecated.5D.5D><code>[[deprecated]]</code></a>
+ attribute and replaced with either references
+ or STL pointers.</li>
+</ul>
+<p>As of C++11, the following are options in the
+place of raw pointers:</p>
+<ul>
+ <li><code>std::unique_ptr</code> Should be used
+ when you still need to use a pointer, but you
+ only need one entity to own the pointer. The
+ <code>std::unique_ptr</code> will automatically
+ be deleted when there are no more references to
+ it.</li>
+ <li><code>std::shared_ptr</code> Should be used
+ when you still need to use a pointer and you
+ need many references to the object. When
+ there are zero remaining references to the
+ object, it will be deleted. Use <code>std::weak_ptr</code>
+ where necessary to avoid circular dependencies
+ or other potential issues.</li>
+ <li>L-value references (the traditional sort
+ of reference that has been around since before C++11)
+ should be used when you want to pass around a
+ reference to an object and want to guarantee
+ that it won't be null. Use const references
+ if you want to avoid copying a large object
+ but don't want to modify it.</li>
+ <li>R-value references were introduced in C++11
+ and allow for the use of <code>std::move</code>.
+ R-value references should be used where it makes
+ sense that a parameter to a function is having
+ its ownership passed from one place to another.
+ In general, R-value references are not inherently
+ bad, but they do introduce additional complexity
+ that may confuse people who are not familiar
+ with them.</li>
+</ul>
+
+<h3 id="Deprecation">Deprecation</h3>
+<p>When updating APIs, make liberal use of the
+<code>[[deprecated]]</code> attribute (although if
+it is reasonable to simply remove any old interfaces
+then do so) to indicate that users should no longer
+use the function. Currently, this will cause warnings
+in user code and errors in the WPILib build.</p>
+
+<pre>
+[[deprecated("This is a deprecated function; this text will be displayed when"
+ " the compiler throws a warning.")]]
+void foo() {}
+class [[deprecated("This is a deprecated class.")]] Foo {};
+int bar [[deprecated("This is a deprecated variable.")]];
+</pre>
+
+<p>See <a href=http://josephmansfield.uk/articles/marking-deprecated-c++14.html>
+here</a> for more information on deprecation.</p>
+
+<h2 id="Header_Files">Header Files</h2>
+
+<p>In general, every <code>.cc</code> file should have an
+associated <code>.h</code> file. There are some common
+exceptions, such as unittests and
+small <code>.cpp</code> files containing just a
+<code>main()</code> function.</p>
+
+<p>Correct use of header files can make a huge difference to
+the readability, size and performance of your code.</p>
+
+<p>The following rules will guide you through the various
+pitfalls of using header files.</p>
+
+<a id="The_-inl.h_Files"></a>
+<h3 id="Self_contained_Headers">Self-contained Headers</h3>
+
+<div class="summary">
+<p>Header files should be self-contained and end in <code>.h</code>. Files that
+are meant for textual inclusion, but are not headers, should end in
+<code>.inc</code>. Separate <code>-inl.h</code> headers are disallowed.</p>
+</div>
+
+<div class="stylebody">
+<p>All header files should be self-contained. In other
+words, users and refactoring tools should not have to adhere to special
+conditions in order to include the header. Specifically, a
+header should have <a href="#The__define_Guard">header guards</a>,
+should include all other headers it needs, and should not require any
+particular symbols to be defined.</p>
+
+<p>There are rare cases where a file is not meant to be self-contained, but
+instead is meant to be textually included at a specific point in the code.
+Examples are files that need to be included multiple times or
+platform-specific extensions that essentially are part of other headers. Such
+files should use the file extension <code>.inc</code>.</p>
+
+<p>If a template or inline function is declared in a <code>.h</code> file,
+define it in that same file. The definitions of these constructs must
+be included into every <code>.cc</code> file that uses them, or the
+program may fail to link in some build configurations. Do not move these
+definitions to separate <code>-inl.h</code> files.</p>
+
+<p>As an exception, a function template that is explicitly
+instantiated for all relevant sets of template arguments, or
+that is a private member of a class, may
+be defined in the only <code>.cc</code> file that
+instantiates the template.</p>
+
+</div>
+
+<h3 id="The__define_Guard">The #define Guard</h3>
+
+<div class="summary">
+<p>All header files should have <code>#define</code> guards to
+prevent multiple inclusion. The format of the symbol name
+should be
+<code><i><PROJECT></i>_<i><PATH></i>_<i><FILE></i>_H_</code>.</p>
+</div>
+
+<div class="stylebody">
+
+
+
+<p>To guarantee uniqueness, they should
+be based on the full path in a project's source tree. For
+example, the file <code>foo/src/bar/baz.h</code> in
+project <code>foo</code> should have the following
+guard:</p>
+
+<pre>#ifndef FOO_BAR_BAZ_H_
+#define FOO_BAR_BAZ_H_
+
+...
+
+#endif // FOO_BAR_BAZ_H_
+</pre>
+
+
+
+
+</div>
+
+<h3 id="Forward_Declarations">Forward Declarations</h3>
+
+<div class="summary">
+<p>You may forward declare ordinary classes in order to avoid
+unnecessary <code>#include</code>s.</p>
+</div>
+
+<div class="stylebody">
+
+<div class="definition">
+<p>A "forward declaration" is a declaration of a class,
+function, or template without an associated definition.
+<code>#include</code> lines can often be replaced with
+forward declarations of whatever symbols are actually
+used by the client code.</p>
+</div>
+
+<div class="pros">
+<ul>
+ <li>Unnecessary <code>#include</code>s force the
+ compiler to open more files and process more
+ input.</li>
+
+ <li>They can also force your code to be recompiled more
+ often, due to changes in the header.</li>
+</ul>
+</div>
+
+<div class="cons">
+<ul>
+ <li>It can be difficult to determine the correct form
+ of a forward declaration in the presence of features
+ like templates, typedefs, default parameters, and using
+ declarations.</li>
+
+ <li>It can be difficult to determine whether a forward
+ declaration or a full <code>#include</code> is needed
+ for a given piece of code, particularly when implicit
+ conversion operations are involved. In extreme cases,
+ replacing an <code>#include</code> with a forward
+ declaration can silently change the meaning of
+ code.</li>
+
+ <li>Forward declaring multiple symbols from a header
+ can be more verbose than simply
+ <code>#include</code>ing the header.</li>
+
+ <li>Forward declarations of functions and templates can
+ prevent the header owners from making
+ otherwise-compatible changes to their APIs; for
+ example, widening a parameter type, or adding a
+ template parameter with a default value.</li>
+ <li>Forward declaring symbols from namespace
+ <code>std::</code> usually yields undefined
+ behavior.</li>
+
+ <li>Structuring code to enable forward declarations
+ (e.g. using pointer members instead of object members)
+ can make the code slower and more complex.</li>
+
+ <li>The practical efficiency benefits of forward
+ declarations are unproven.</li>
+</ul>
+</div>
+
+<div class="decision">
+<ul>
+ <li>When using a function declared in a header file,
+ always <code>#include</code> that header.</li>
+
+ <li>When using a class template, prefer to
+ <code>#include</code> its header file.</li>
+
+ <li>When using an ordinary class, relying on a forward
+ declaration is OK, but be wary of situations where a
+ forward declaration may be insufficient or incorrect;
+ when in doubt, just <code>#include</code> the
+ appropriate header.</li>
+
+ <li>Do not replace data members with pointers just to
+ avoid an <code>#include</code>.</li>
+</ul>
+
+<p>Please see <a href="#Names_and_Order_of_Includes">Names and Order
+of Includes</a> for rules about when to #include a header.</p>
+</div>
+
+</div>
+
+<h3 id="Inline_Functions">Inline Functions</h3>
+
+<div class="summary">
+<p>Define functions inline only when they are small, say, 10
+lines or less.</p>
+</div>
+
+<div class="stylebody">
+
+<div class="definition">
+<p>You can declare functions in a way that allows the compiler to expand
+them inline rather than calling them through the usual
+function call mechanism.</p>
+</div>
+
+<div class="pros">
+<p>Inlining a function can generate more efficient object
+code, as long as the inlined function is small. Feel free
+to inline accessors and mutators, and other short,
+performance-critical functions.</p>
+</div>
+
+<div class="cons">
+<p>Overuse of inlining can actually make programs slower.
+Depending on a function's size, inlining it can cause the
+code size to increase or decrease. Inlining a very small
+accessor function will usually decrease code size while
+inlining a very large function can dramatically increase
+code size. On modern processors smaller code usually runs
+faster due to better use of the instruction cache.</p>
+</div>
+
+<div class="decision">
+<p>A decent rule of thumb is to not inline a function if
+it is more than 10 lines long. Beware of destructors,
+which are often longer than they appear because of
+implicit member- and base-destructor calls!</p>
+
+<p>Another useful rule of thumb: it's typically not cost
+effective to inline functions with loops or switch
+statements (unless, in the common case, the loop or
+switch statement is never executed).</p>
+
+<p>It is important to know that functions are not always
+inlined even if they are declared as such; for example,
+virtual and recursive functions are not normally inlined.
+Usually recursive functions should not be inline. The
+main reason for making a virtual function inline is to
+place its definition in the class, either for convenience
+or to document its behavior, e.g., for accessors and
+mutators.</p>
+</div>
+
+</div>
+
+<h3 id="Function_Parameter_Ordering">Function Parameter Ordering</h3>
+
+<div class="summary">
+<p>When defining a function, parameter order is: inputs, then
+outputs.</p>
+</div>
+
+<div class="stylebody">
+<p>Parameters to C/C++ functions are either input to the
+function, output from the function, or both. Input
+parameters are usually values or <code>const</code>
+references, while output and input/output parameters will
+be non-<code>const</code> pointers. When ordering
+function parameters, put all input-only parameters before
+any output parameters. In particular, do not add new
+parameters to the end of the function just because they
+are new; place new input-only parameters before the
+output parameters.</p>
+
+<p>This is not a hard-and-fast rule. Parameters that are
+both input and output (often classes/structs) muddy the
+waters, and, as always, consistency with related
+functions may require you to bend the rule.</p>
+
+</div>
+
+<h3 id="Names_and_Order_of_Includes">Names and Order of Includes</h3>
+
+<div class="summary">
+<p>Use standard order for readability and to avoid hidden
+dependencies: Related header, C library, C++ library, other libraries'
+<code>.h</code>, your project's <code>.h</code>.</p>
+</div>
+
+<div class="stylebody">
+<p>
+All of a project's header files should be
+listed as descendants of the project's source
+directory without use of UNIX directory shortcuts
+<code>.</code> (the current directory) or <code>..</code>
+(the parent directory). For example,
+
+<code>google-awesome-project/src/base/logging.h</code>
+should be included as:</p>
+
+<pre>#include "base/logging.h"
+</pre>
+
+<p>In <code><var>dir/foo</var>.cc</code> or
+<code><var>dir/foo_test</var>.cc</code>, whose main
+purpose is to implement or test the stuff in
+<code><var>dir2/foo2</var>.h</code>, order your includes
+as follows:</p>
+
+<ol>
+ <li><code><var>dir2/foo2</var>.h</code>.</li>
+
+ <li>C system files.</li>
+
+ <li>C++ system files.</li>
+
+ <li>Other libraries' <code>.h</code>
+ files.</li>
+
+ <li>
+ Your project's <code>.h</code>
+ files.</li>
+</ol>
+
+<p>With the preferred ordering, if
+<code><var>dir2/foo2</var>.h</code> omits any necessary
+includes, the build of <code><var>dir/foo</var>.cc</code>
+or <code><var>dir/foo</var>_test.cc</code> will break.
+Thus, this rule ensures that build breaks show up first
+for the people working on these files, not for innocent
+people in other packages.</p>
+
+<p><code><var>dir/foo</var>.cc</code> and
+<code><var>dir2/foo2</var>.h</code> are usually in the same
+directory (e.g. <code>base/basictypes_test.cc</code> and
+<code>base/basictypes.h</code>), but may sometimes be in different
+directories too.</p>
+
+
+
+<p>Within each section the includes should be ordered
+alphabetically. Note that older code might not conform to
+this rule and should be fixed when convenient.</p>
+
+<p>You should include all the headers that define the symbols you rely
+upon (except in cases of <a href="#Forward_Declarations">forward
+declaration</a>). If you rely on symbols from <code>bar.h</code>,
+don't count on the fact that you included <code>foo.h</code> which
+(currently) includes <code>bar.h</code>: include <code>bar.h</code>
+yourself, unless <code>foo.h</code> explicitly demonstrates its intent
+to provide you the symbols of <code>bar.h</code>. However, any
+includes present in the related header do not need to be included
+again in the related <code>cc</code> (i.e., <code>foo.cc</code> can
+rely on <code>foo.h</code>'s includes).</p>
+
+<p>For example, the includes in
+
+<code>google-awesome-project/src/foo/internal/fooserver.cc</code>
+might look like this:</p>
+
+
+<pre>#include "foo/server/fooserver.h"
+
+#include <sys/types.h>
+#include <unistd.h>
+#include <hash_map>
+#include <vector>
+
+#include "base/basictypes.h"
+#include "base/commandlineflags.h"
+#include "foo/server/bar.h"
+</pre>
+
+<p class="exception">Sometimes, system-specific code needs
+conditional includes. Such code can put conditional
+includes after other includes. Of course, keep your
+system-specific code small and localized. Example:</p>
+
+<pre>#include "foo/public/fooserver.h"
+
+#include "base/port.h" // For LANG_CXX11.
+
+#ifdef LANG_CXX11
+#include <initializer_list>
+#endif // LANG_CXX11
+</pre>
+
+</div>
+
+<h2 id="Naming">Naming</h2>
+
+<p>The most important consistency rules are those that govern
+naming. The style of a name immediately informs us what sort of
+thing the named entity is: a type, a variable, a function, a
+constant, a macro, etc., without requiring us to search for the
+declaration of that entity. The pattern-matching engine in our
+brains relies a great deal on these naming rules.
+</p>
+
+<p>Naming rules are pretty arbitrary, but
+ we feel that
+consistency is more important than individual preferences in this
+area, so regardless of whether you find them sensible or not,
+the rules are the rules.</p>
+
+<h3 id="General_Naming_Rules">General Naming Rules</h3>
+
+<div class="summary">
+<p>Function names, variable names, and filenames should be
+descriptive; eschew abbreviation.</p>
+</div>
+
+<div class="stylebody">
+<p>Give as descriptive a name as possible, within reason.
+Do not worry about saving horizontal space as it is far
+more important to make your code immediately
+understandable by a new reader. Do not use abbreviations
+that are ambiguous or unfamiliar to readers outside your
+project, and do not abbreviate by deleting letters within
+a word.</p>
+
+<pre>int price_count_reader; // No abbreviation.
+int num_errors; // "num" is a widespread convention.
+int num_dns_connections; // Most people know what "DNS" stands for.
+</pre>
+
+<pre class="badcode">int n; // Meaningless.
+int nerr; // Ambiguous abbreviation.
+int n_comp_conns; // Ambiguous abbreviation.
+int wgc_connections; // Only your group knows what this stands for.
+int pc_reader; // Lots of things can be abbreviated "pc".
+int cstmr_id; // Deletes internal letters.
+</pre>
+
+</div>
+
+<h3 id="File_Names">File Names</h3>
+
+<div class="summary">
+<p>Filenames should be all lowercase and can include
+underscores (<code>_</code>) or dashes (<code>-</code>).
+Follow the convention that your
+
+project uses. If there is no consistent
+local pattern to follow, prefer "_".</p>
+</div>
+
+<div class="stylebody">
+
+<p>Examples of acceptable file names:</p>
+
+<ul>
+ <li><code>my_useful_class.cc</code></li>
+ <li><code>my-useful-class.cc</code></li>
+ <li><code>myusefulclass.cc</code></li>
+ <li><code>myusefulclass_test.cc // _unittest and _regtest are deprecated.</code></li>
+</ul>
+
+<p>C++ files should end in <code>.cc</code> and header files should end in
+<code>.h</code>. Files that rely on being textually included at specific points
+should end in <code>.inc</code> (see also the section on
+<a href="#Self_contained_Headers">self-contained headers</a>).</p>
+
+<p>Do not use filenames that already exist in
+<code>/usr/include</code>, such as <code>db.h</code>.</p>
+
+<p>In general, make your filenames very specific. For
+example, use <code>http_server_logs.h</code> rather than
+<code>logs.h</code>. A very common case is to have a pair
+of files called, e.g., <code>foo_bar.h</code> and
+<code>foo_bar.cc</code>, defining a class called
+<code>FooBar</code>.</p>
+
+<p>Inline functions must be in a <code>.h</code> file. If
+your inline functions are very short, they should go
+directly into your <code>.h</code> file. </p>
+
+</div>
+
+<h3 id="Type_Names">Type Names</h3>
+
+<div class="summary">
+<p>Type names start with a capital letter and have a capital
+letter for each new word, with no underscores:
+<code>MyExcitingClass</code>, <code>MyExcitingEnum</code>.</p>
+</div>
+
+<div class="stylebody">
+
+<p>The names of all types — classes, structs, typedefs,
+and enums — have the same naming convention. Type names
+should start with a capital letter and have a capital letter
+for each new word. No underscores. For example:</p>
+
+<pre>// classes and structs
+class UrlTable { ...
+class UrlTableTester { ...
+struct UrlTableProperties { ...
+
+// typedefs
+typedef hash_map<UrlTableProperties *, string> PropertiesMap;
+
+// enums
+enum UrlTableErrors { ...
+</pre>
+
+</div>
+
+<h3 id="Variable_Names">Variable Names</h3>
+
+<div class="summary">
+<p>The names of variables and data members are all lowercase, with
+underscores between words. Data members of classes (but not structs)
+additionally are prefixed with "m_". For instance:
+<code>a_local_variable</code>, <code>a_struct_data_member</code>,
+<code>m_a_class_data_member</code>.</p>
+</div>
+
+<div class="stylebody">
+
+<h4 class="stylepoint_subsection">Common Variable names</h4>
+
+<p>For example:</p>
+
+<pre>string table_name; // OK - uses underscore.
+string tablename; // OK - all lowercase.
+</pre>
+
+<pre class="badcode">string tableName; // Bad - mixed case.
+</pre>
+
+<h4 class="stylepoint_subsection">Class Data Members</h4>
+
+<p>Data members of classes, both static and non-static, are
+named like ordinary nonmember variables, but prefixed with a
+"m_".</p>
+
+<pre>class TableInfo {
+ ...
+ private:
+ string m_table_name; // OK - m_ at beginning.
+ string m_tablename; // OK.
+ static Pool<TableInfo>* m_pool; // OK.
+};
+</pre>
+
+<h4 class="stylepoint_subsection">Struct Data Members</h4>
+
+<p>Data members of structs, both static and non-static,
+are named like ordinary nonmember variables. They do not have
+the preceding "m_" that data members in classes have.</p>
+
+<pre>struct UrlTableProperties {
+ string name;
+ int num_entries;
+ static Pool<UrlTableProperties>* pool;
+};
+</pre>
+
+
+<p>See <a href="#Structs_vs._Classes">Structs vs.
+Classes</a> for a discussion of when to use a struct
+versus a class.</p>
+
+<h4 class="stylepoint_subsection">Global Variables</h4>
+
+<p>There are no special requirements for global
+variables, which should be rare in any case, but if you
+use one, consider prefixing it with <code>g_</code> or
+some other marker to easily distinguish it from local
+variables.</p>
+
+</div>
+
+<h3 id="Constant_Names">Constant Names</h3>
+
+<div class="summary">
+<p>Use a <code>k</code> followed by mixed case, e.g.,
+<code>kDaysInAWeek</code>, for constants defined globally or within a class.</p>
+</div>
+
+<div class="stylebody">
+
+<p>As a convenience to the reader, compile-time constants of global or class scope
+follow a different naming convention from other variables.
+Use a <code>k</code> followed by words with uppercase first letters:</p>
+
+<pre>const int kDaysInAWeek = 7;
+</pre>
+
+<p>This convention may optionally be used for compile-time constants of local scope;
+otherwise the usual variable naming rules apply.
+
+</p></div>
+
+<h3 id="Function_Names">Function Names</h3>
+
+<div class="summary">
+<p>Regular functions have mixed case; accessors and mutators
+match the name of the variable:
+<code>MyExcitingFunction()</code>,
+<code>MyExcitingMethod()</code>,
+<code>my_exciting_member_variable()</code>,
+<code>set_my_exciting_member_variable()</code>.</p>
+</div>
+
+<div class="stylebody">
+
+<h4 class="stylepoint_subsection">Regular Functions</h4>
+
+<p>Functions should start with a capital letter and have
+a capital letter for each new word. No underscores.</p>
+
+<p>If your function crashes upon an error, you should
+append OrDie to the function name. This only applies to
+functions which could be used by production code and to
+errors that are reasonably likely to occur during normal
+operation.</p>
+
+ <pre>AddTableEntry()
+DeleteUrl()
+OpenFileOrDie()
+</pre>
+
+<h4 class="stylepoint_subsection">Accessors and Mutators</h4>
+
+<p>Accessors and mutators (get and set functions) should
+match the name of the variable they are getting and
+setting. This shows an excerpt of a class whose instance
+variable is <code>num_entries_</code>.</p>
+
+<pre>class MyClass {
+ public:
+ ...
+ int num_entries() const { return num_entries_; }
+ void set_num_entries(int num_entries) { num_entries_ = num_entries; }
+
+ private:
+ int num_entries_;
+};
+</pre>
+
+<p>You may also use lowercase letters for other very
+short inlined functions. For example if a function were
+so cheap you would not cache the value if you were
+calling it in a loop, then lowercase naming would be
+acceptable.</p>
+
+</div>
+
+<h3 id="Namespace_Names">Namespace Names</h3>
+
+<div class="summary">
+
+
+<p>Namespace names are all lower-case,
+and based on project names and possibly their directory
+structure: <code>google_awesome_project</code>.</p>
+</div>
+
+<div class="stylebody">
+
+<p>See <a href="#Namespaces">Namespaces</a> for a
+discussion of namespaces and how to name them.</p>
+
+</div>
+
+<h3 id="Enumerator_Names">Enumerator Names</h3>
+
+<div class="summary">
+<p>Enumerators should be named <i>either</i> like
+<a href="#Constant_Names">constants</a> or like
+<a href="#Macro_Names">macros</a>: either <code>kEnumName</code> or
+<code>ENUM_NAME</code>.</p>
+</div>
+
+<div class="stylebody">
+
+<p>Preferably, the individual enumerators should be named
+like <a href="#Constant_Names">constants</a>. However, it
+is also acceptable to name them like
+<a href="Macro_Names">macros</a>. The enumeration name,
+<code>UrlTableErrors</code> (and
+<code>AlternateUrlTableErrors</code>), is a type, and
+therefore mixed case.</p>
+
+<pre>enum UrlTableErrors {
+ kOK = 0,
+ kErrorOutOfMemory,
+ kErrorMalformedInput,
+};
+enum AlternateUrlTableErrors {
+ OK = 0,
+ OUT_OF_MEMORY = 1,
+ MALFORMED_INPUT = 2,
+};
+</pre>
+
+<p>Until January 2009, the style was to name enum values
+like <a href="#Macro_Names">macros</a>. This caused
+problems with name collisions between enum values and
+macros. Hence, the change to prefer constant-style naming
+was put in place. New code should prefer constant-style
+naming if possible. However, there is no reason to change
+old code to use constant-style names, unless the old
+names are actually causing a compile-time problem.</p>
+
+
+
+</div>
+
+<h3 id="Macro_Names">Macro Names</h3>
+
+<div class="summary">
+<p>You're not really going to <a href="#Preprocessor_Macros">
+define a macro</a>, are you? If you do, they're like this:
+<code>MY_MACRO_THAT_SCARES_SMALL_CHILDREN</code>.</p>
+</div>
+
+<div class="stylebody">
+
+<p>Please see the <a href="#Preprocessor_Macros">description
+of macros</a>; in general macros should <em>not</em> be used.
+However, if they are absolutely needed, then they should be
+named with all capitals and underscores.</p>
+
+<pre>#define ROUND(x) ...
+#define PI_ROUNDED 3.0
+</pre>
+
+</div>
+
+<h3 id="Exceptions_to_Naming_Rules">Exceptions to Naming Rules</h3>
+
+<div class="summary">
+<p>If you are naming something that is analogous to an
+existing C or C++ entity then you can follow the existing
+naming convention scheme.</p>
+</div>
+
+<div class="stylebody">
+
+<dl>
+ <dt><code>bigopen()</code></dt>
+ <dd>function name, follows form of <code>open()</code></dd>
+
+ <dt><code>uint</code></dt>
+ <dd><code>typedef</code></dd>
+
+ <dt><code>bigpos</code></dt>
+ <dd><code>struct</code> or <code>class</code>, follows
+ form of <code>pos</code></dd>
+
+ <dt><code>sparse_hash_map</code></dt>
+ <dd>STL-like entity; follows STL naming conventions</dd>
+
+ <dt><code>LONGLONG_MAX</code></dt>
+ <dd>a constant, as in <code>INT_MAX</code></dd>
+</dl>
+
+</div>
+
+<h2 id="Comments">Comments</h2>
+
+<p>Though a pain to write, comments are absolutely vital to
+keeping our code readable. The following rules describe what
+you should comment and where. But remember: while comments are
+very important, the best code is self-documenting. Giving
+sensible names to types and variables is much better than using
+obscure names that you must then explain through comments.</p>
+
+<p>When writing your comments, write for your audience: the
+next
+contributor who will need to
+understand your code. Be generous — the next
+one may be you!</p>
+
+<h3 id="Comment_Style">Comment Style</h3>
+
+<div class="summary">
+<p>Use either the <code>//</code> or <code>/* */</code>
+syntax, as long as you are consistent.</p>
+</div>
+
+<div class="stylebody">
+
+<p>You can use either the <code>//</code> or the <code>/*
+*/</code> syntax; however, <code>//</code> is
+<em>much</em> more common. Be consistent with how you
+comment and what style you use where.</p>
+
+</div>
+
+<h3 id="File_Comments">File Comments</h3>
+
+<div class="summary">
+<p> Start each file with license
+boilerplate, followed by a description of its
+contents.</p>
+</div>
+
+<div class="stylebody">
+
+<h4 class="stylepoint_subsection">Legal Notice and Author
+Line</h4>
+
+
+
+<p>Every file should contain license
+boilerplate. Choose the appropriate boilerplate for the
+license used by the project (for example, Apache 2.0,
+BSD, LGPL, GPL).</p>
+
+<p>If you make significant changes to a file with an
+author line, consider deleting the author line.</p>
+
+<h4 class="stylepoint_subsection">File Contents</h4>
+
+<p>Every file should have a comment at the top describing
+its contents.</p>
+
+<p>Generally a <code>.h</code> file will describe the
+classes that are declared in the file with an overview of
+what they are for and how they are used. A
+<code>.cc</code> file should contain more information
+about implementation details or discussions of tricky
+algorithms. If you feel the implementation details or a
+discussion of the algorithms would be useful for someone
+reading the <code>.h</code>, feel free to put it there
+instead, but mention in the <code>.cc</code> that the
+documentation is in the <code>.h</code> file.</p>
+
+<p>Do not duplicate comments in both the <code>.h</code>
+and the <code>.cc</code>. Duplicated comments
+diverge.</p>
+
+</div>
+
+<h3 id="Class_Comments">Class Comments</h3>
+
+<div class="summary">
+<p>Every class definition should have an accompanying comment
+that describes what it is for and how it should be used.</p>
+</div>
+
+<div class="stylebody">
+
+<pre>// Iterates over the contents of a GargantuanTable. Sample usage:
+// GargantuanTableIterator* iter = table->NewIterator();
+// for (iter->Seek("foo"); !iter->done(); iter->Next()) {
+// process(iter->key(), iter->value());
+// }
+// delete iter;
+class GargantuanTableIterator {
+ ...
+};
+</pre>
+
+<p>If you have already described a class in detail in the
+comments at the top of your file feel free to simply
+state "See comment at top of file for a complete
+description", but be sure to have some sort of
+comment.</p>
+
+<p>Document the synchronization assumptions the class
+makes, if any. If an instance of the class can be
+accessed by multiple threads, take extra care to document
+the rules and invariants surrounding multithreaded
+use.</p>
+
+</div>
+
+<h3 id="Function_Comments">Function Comments</h3>
+
+<div class="summary">
+<p>Declaration comments describe use of the function; comments
+at the definition of a function describe operation.</p>
+</div>
+
+<div class="stylebody">
+
+<h4 class="stylepoint_subsection">Function Declarations</h4>
+
+<p>Every function declaration should have comments
+immediately preceding it that describe what the function
+does and how to use it. These comments should be
+descriptive ("Opens the file") rather than imperative
+("Open the file"); the comment describes the function, it
+does not tell the function what to do. In general, these
+comments do not describe how the function performs its
+task. Instead, that should be left to comments in the
+function definition.</p>
+
+<p>Types of things to mention in comments at the function
+declaration:</p>
+
+<ul>
+ <li>What the inputs and outputs are.</li>
+
+ <li>For class member functions: whether the object
+ remembers reference arguments beyond the duration of
+ the method call, and whether it will free them or
+ not.</li>
+
+ <li>If the function allocates memory that the caller
+ must free.</li>
+
+ <li>Whether any of the arguments can be a null
+ pointer.</li>
+
+ <li>If there are any performance implications of how a
+ function is used.</li>
+
+ <li>If the function is re-entrant. What are its
+ synchronization assumptions?</li>
+ </ul>
+
+<p>Here is an example:</p>
+
+<pre>// Returns an iterator for this table. It is the client's
+// responsibility to delete the iterator when it is done with it,
+// and it must not use the iterator once the GargantuanTable object
+// on which the iterator was created has been deleted.
+//
+// The iterator is initially positioned at the beginning of the table.
+//
+// This method is equivalent to:
+// Iterator* iter = table->NewIterator();
+// iter->Seek("");
+// return iter;
+// If you are going to immediately seek to another place in the
+// returned iterator, it will be faster to use NewIterator()
+// and avoid the extra seek.
+Iterator* GetIterator() const;
+</pre>
+
+<p>However, do not be unnecessarily verbose or state the
+completely obvious. Notice below that it is not necessary
+ to say "returns false otherwise" because this is
+implied.</p>
+
+<pre>// Returns true if the table cannot hold any more entries.
+bool IsTableFull();
+</pre>
+
+<p>When commenting constructors and destructors, remember
+that the person reading your code knows what constructors
+and destructors are for, so comments that just say
+something like "destroys this object" are not useful.
+Document what constructors do with their arguments (for
+example, if they take ownership of pointers), and what
+cleanup the destructor does. If this is trivial, just
+skip the comment. It is quite common for destructors not
+to have a header comment.</p>
+
+<h4 class="stylepoint_subsection">Function Definitions</h4>
+
+<p>If there is anything tricky about how a function does
+its job, the function definition should have an
+explanatory comment. For example, in the definition
+comment you might describe any coding tricks you use,
+give an overview of the steps you go through, or explain
+why you chose to implement the function in the way you
+did rather than using a viable alternative. For instance,
+you might mention why it must acquire a lock for the
+first half of the function but why it is not needed for
+the second half.</p>
+
+<p>Note you should <em>not</em> just repeat the comments
+given with the function declaration, in the
+<code>.h</code> file or wherever. It's okay to
+recapitulate briefly what the function does, but the
+focus of the comments should be on how it does it.</p>
+
+</div>
+
+<h3 id="Variable_Comments">Variable Comments</h3>
+
+<div class="summary">
+<p>In general the actual name of the variable should be
+descriptive enough to give a good idea of what the variable
+is used for. In certain cases, more comments are required.</p>
+</div>
+
+<div class="stylebody">
+
+<h4 class="stylepoint_subsection">Class Data Members</h4>
+
+<p>Each class data member (also called an instance
+variable or member variable) should have a comment
+describing what it is used for. If the variable can take
+sentinel values with special meanings, such as a null
+pointer or -1, document this. For example:</p>
+
+
+<pre>private:
+ // Keeps track of the total number of entries in the table.
+ // Used to ensure we do not go over the limit. -1 means
+ // that we don't yet know how many entries the table has.
+ int num_total_entries_;
+</pre>
+
+<h4 class="stylepoint_subsection">Global Variables</h4>
+
+<p>As with data members, all global variables should have
+a comment describing what they are and what they are used
+for. For example:</p>
+
+<pre>// The total number of tests cases that we run through in this regression test.
+const int kNumTestCases = 6;
+</pre>
+
+</div>
+
+<h3 id="Implementation_Comments">Implementation Comments</h3>
+
+<div class="summary">
+<p>In your implementation you should have comments in tricky,
+non-obvious, interesting, or important parts of your code.</p>
+</div>
+
+<div class="stylebody">
+
+<h4 class="stylepoint_subsection">Explanatory Comments</h4>
+
+<p>Tricky or complicated code blocks should have comments
+before them. Example:</p>
+
+<pre>// Divide result by two, taking into account that x
+// contains the carry from the add.
+for (int i = 0; i < result->size(); i++) {
+ x = (x << 8) + (*result)[i];
+ (*result)[i] = x >> 1;
+ x &= 1;
+}
+</pre>
+
+<h4 class="stylepoint_subsection">Line Comments</h4>
+
+<p>Also, lines that are non-obvious should get a comment
+at the end of the line. These end-of-line comments should
+be separated from the code by 2 spaces. Example:</p>
+
+<pre>// If we have enough memory, mmap the data portion too.
+mmap_budget = max<int64>(0, mmap_budget - index_->length());
+if (mmap_budget >= data_size_ && !MmapData(mmap_chunk_bytes, mlock))
+ return; // Error already logged.
+</pre>
+
+<p>Note that there are both comments that describe what
+the code is doing, and comments that mention that an
+error has already been logged when the function
+returns.</p>
+
+<p>If you have several comments on subsequent lines, it
+can often be more readable to line them up:</p>
+
+<pre>DoSomething(); // Comment here so the comments line up.
+DoSomethingElseThatIsLonger(); // Two spaces between the code and the comment.
+{ // One space before comment when opening a new scope is allowed,
+ // thus the comment lines up with the following comments and code.
+ DoSomethingElse(); // Two spaces before line comments normally.
+}
+vector<string> list{// Comments in braced lists describe the next element ..
+ "First item",
+ // .. and should be aligned appropriately.
+ "Second item"};
+DoSomething(); /* For trailing block comments, one space is fine. */
+</pre>
+
+<h4 class="stylepoint_subsection">nullptr/NULL, true/false, 1, 2, 3...</h4>
+
+<p>When you pass in a null pointer, boolean, or literal
+integer values to functions, you should consider adding a
+comment about what they are, or make your code
+self-documenting by using constants. For example,
+compare:</p>
+
+<pre class="badcode">bool success = CalculateSomething(interesting_value,
+ 10,
+ false,
+ NULL); // What are these arguments??
+</pre>
+
+<p>versus:</p>
+
+<pre>bool success = CalculateSomething(interesting_value,
+ 10, // Default base value.
+ false, // Not the first time we're calling this.
+ NULL); // No callback.
+</pre>
+
+<p>Or alternatively, constants or self-describing variables:</p>
+
+<pre>const int kDefaultBaseValue = 10;
+const bool kFirstTimeCalling = false;
+Callback *null_callback = NULL;
+bool success = CalculateSomething(interesting_value,
+ kDefaultBaseValue,
+ kFirstTimeCalling,
+ null_callback);
+</pre>
+
+<h4 class="stylepoint_subsection">Don'ts</h4>
+
+<p>Note that you should <em>never</em> describe the code
+itself. Assume that the person reading the code knows C++
+better than you do, even though he or she does not know
+what you are trying to do:</p>
+
+<pre class="badcode">// Now go through the b array and make sure that if i occurs,
+// the next element is i+1.
+... // Geez. What a useless comment.
+</pre>
+
+</div>
+
+<h3 id="Punctuation,_Spelling_and_Grammar">Punctuation, Spelling and Grammar</h3>
+
+<div class="summary">
+<p>Pay attention to punctuation, spelling, and grammar; it is
+easier to read well-written comments than badly written
+ones.</p>
+</div>
+
+<div class="stylebody">
+
+<p>Comments should be as readable as narrative text, with
+proper capitalization and punctuation. In many cases,
+complete sentences are more readable than sentence
+fragments. Shorter comments, such as comments at the end
+of a line of code, can sometimes be less formal, but you
+should be consistent with your style.</p>
+
+<p>Although it can be frustrating to have a code reviewer
+point out that you are using a comma when you should be
+using a semicolon, it is very important that source code
+maintain a high level of clarity and readability. Proper
+punctuation, spelling, and grammar help with that
+goal.</p>
+
+</div>
+
+<h3 id="TODO_Comments">TODO Comments</h3>
+
+<div class="summary">
+<p>Use <code>TODO</code> comments for code that is temporary,
+a short-term solution, or good-enough but not perfect.</p>
+</div>
+
+<div class="stylebody">
+
+<p><code>TODO</code>s should include the string
+<code>TODO</code> in all caps, followed by the
+
+name, e-mail address, or other
+identifier of the person
+ with the best context
+about the problem referenced by the <code>TODO</code>. The
+main purpose is to have a consistent <code>TODO</code> that
+can be searched to find out how to get more details upon
+request. A <code>TODO</code> is not a commitment that the
+person referenced will fix the problem. Thus when you create
+a <code>TODO</code>, it is almost always your
+
+name
+that is given.</p>
+
+
+
+<div>
+<pre>// TODO(kl@gmail.com): Use a "*" here for concatenation operator.
+// TODO(Zeke) change this to use relations.
+</pre>
+</div>
+
+<p>If your <code>TODO</code> is of the form "At a future
+date do something" make sure that you either include a
+very specific date ("Fix by November 2005") or a very
+specific event ("Remove this code when all clients can
+handle XML responses.").</p>
+
+</div>
+
+<h3 id="Deprecation_Comments">Deprecation Comments</h3>
+
+<div class="summary">
+<p>Mark deprecated interface points with <code>DEPRECATED</code>
+comments.</p>
+</div>
+
+<div class="stylebody">
+
+<p>You can mark an interface as deprecated by writing a
+comment containing the word <code>DEPRECATED</code> in
+all caps. The comment goes either before the declaration
+of the interface or on the same line as the
+declaration.</p>
+
+
+
+<p>After the word
+<code>DEPRECATED</code>, write your name, e-mail address,
+or other identifier in parentheses.</p>
+
+<p>A deprecation comment must include simple, clear
+directions for people to fix their callsites. In C++, you
+can implement a deprecated function as an inline function
+that calls the new interface point.</p>
+
+<p>Marking an interface point <code>DEPRECATED</code>
+will not magically cause any callsites to change. If you
+want people to actually stop using the deprecated
+facility, you will have to fix the callsites yourself or
+recruit a crew to help you.</p>
+
+<p>New code should not contain calls to deprecated
+interface points. Use the new interface point instead. If
+you cannot understand the directions, find the person who
+created the deprecation and ask them for help using the
+new interface point.</p>
+
+
+
+</div>
+
+<h2 id="Formatting">Formatting</h2>
+
+<p>Coding style and formatting are pretty arbitrary, but a
+
+project is much easier to follow
+if everyone uses the same style. Individuals may not agree with every
+aspect of the formatting rules, and some of the rules may take
+some getting used to, but it is important that all
+
+project contributors follow the
+style rules so that
+they can all read and understand
+everyone's code easily.</p>
+
+
+
+<p>To help you format code correctly, we've
+created a
+<a href="http://google-styleguide.googlecode.com/svn/trunk/google-c-style.el">
+settings file for emacs</a>.</p>
+
+<h3 id="Line_Length">Line Length</h3>
+
+<div class="summary">
+<p>Each line of text in your code should be at most 80
+characters long.</p>
+</div>
+
+<div class="stylebody">
+
+
+
+ <p>We recognize that this rule is
+controversial, but so much existing code already adheres
+to it, and we feel that consistency is important.</p>
+
+<div class="pros">
+<p>Those who favor this rule
+argue that it is rude to force them to resize
+their windows and there is no need for anything longer.
+Some folks are used to having several code windows
+side-by-side, and thus don't have room to widen their
+windows in any case. People set up their work environment
+assuming a particular maximum window width, and 80
+columns has been the traditional standard. Why change
+it?</p>
+</div>
+
+<div class="cons">
+<p>Proponents of change argue that a wider line can make
+code more readable. The 80-column limit is an hidebound
+throwback to 1960s mainframes; modern equipment has wide screens that
+can easily show longer lines.</p>
+</div>
+
+<div class="decision">
+<p> 80 characters is the maximum.</p>
+
+<p class="exception">If a comment line contains an example
+command or a literal URL longer than 80 characters, that
+line may be longer than 80 characters for ease of cut and
+paste.</p>
+
+<p class="exception">A raw-string literal may have content
+that exceeds 80 characters. Except for test code, such literals
+should appear near top of a file.</p>
+
+<p class="exception">An <code>#include</code> statement with a
+long path may exceed 80 columns.</p>
+
+<p class="exception">You needn't be concerned about
+<a href="#The__define_Guard">header guards</a> that exceed
+the maximum length. </p>
+</div>
+
+</div>
+
+<h3 id="Non-ASCII_Characters">Non-ASCII Characters</h3>
+
+<div class="summary">
+<p>Non-ASCII characters should be rare, and must use UTF-8
+formatting.</p>
+</div>
+
+<div class="stylebody">
+
+<p>You shouldn't hard-code user-facing text in source,
+even English, so use of non-ASCII characters should be
+rare. However, in certain cases it is appropriate to
+include such words in your code. For example, if your
+code parses data files from foreign sources, it may be
+appropriate to hard-code the non-ASCII string(s) used in
+those data files as delimiters. More commonly, unittest
+code (which does not need to be localized) might
+contain non-ASCII strings. In such cases, you should use
+UTF-8, since that is an encoding
+understood by most tools able to handle more than just
+ASCII.</p>
+
+<p>Hex encoding is also OK, and encouraged where it
+enhances readability — for example,
+<code>"\xEF\xBB\xBF"</code>, or, even more simply,
+<code>u8"\uFEFF"</code>, is the Unicode zero-width
+no-break space character, which would be invisible if
+included in the source as straight UTF-8.</p>
+
+<p>Use the <code>u8</code> prefix
+to guarantee that a string literal containing
+<code>\uXXXX</code> escape sequences is encoded as UTF-8.
+Do not use it for strings containing non-ASCII characters
+encoded as UTF-8, because that will produce incorrect
+output if the compiler does not interpret the source file
+as UTF-8. </p>
+
+<p>You shouldn't use the C++11 <code>char16_t</code> and
+<code>char32_t</code> character types, since they're for
+non-UTF-8 text. For similar reasons you also shouldn't
+use <code>wchar_t</code> (unless you're writing code that
+interacts with the Windows API, which uses
+<code>wchar_t</code> extensively).</p>
+
+</div>
+
+<h3 id="Spaces_vs._Tabs">Spaces vs. Tabs</h3>
+
+<div class="summary">
+<p>Use only spaces, and indent 2 spaces at a time.</p>
+</div>
+
+<div class="stylebody">
+
+<p>We use spaces for indentation. Do not use tabs in your
+code. You should set your editor to emit spaces when you
+hit the tab key.</p>
+
+</div>
+
+<h3 id="Function_Declarations_and_Definitions">Function Declarations and Definitions</h3>
+
+<div class="summary">
+<p>Return type on the same line as function name, parameters
+on the same line if they fit. Wrap parameter lists which do
+not fit on a single line as you would wrap arguments in a
+function call.</p>
+</div>
+
+<div class="stylebody">
+
+<p>Functions look like this:</p>
+
+
+<pre>ReturnType ClassName::FunctionName(Type par_name1, Type par_name2) {
+ DoSomething();
+ ...
+}
+</pre>
+
+<p>If you have too much text to fit on one line:</p>
+
+<pre>ReturnType ClassName::ReallyLongFunctionName(Type par_name1, Type par_name2,
+ Type par_name3) {
+ DoSomething();
+ ...
+}
+</pre>
+
+<p>or if you cannot fit even the first parameter:</p>
+
+<pre>ReturnType LongClassName::ReallyReallyReallyLongFunctionName(
+ Type par_name1, // 4 space indent
+ Type par_name2,
+ Type par_name3) {
+ DoSomething(); // 2 space indent
+ ...
+}
+</pre>
+
+<p>Some points to note:</p>
+
+<ul>
+ <li>If you cannot fit the return type and the function
+ name on a single line, break between them.</li>
+
+ <li>If you break after the return type of a function
+ declaration or definition, do not indent.</li>
+
+ <li>The open parenthesis is always on the same line as
+ the function name.</li>
+
+ <li>There is never a space between the function name
+ and the open parenthesis.</li>
+
+ <li>There is never a space between the parentheses and
+ the parameters.</li>
+
+ <li>The open curly brace is always at the end of the
+ same line as the last parameter.</li>
+
+ <li>The close curly brace is either on the last line by
+ itself or (if other style rules permit) on the same
+ line as the open curly brace.</li>
+
+ <li>There should be a space between the close
+ parenthesis and the open curly brace.</li>
+
+ <li>All parameters should be named, with identical
+ names in the declaration and implementation.</li>
+
+ <li>All parameters should be aligned if possible.</li>
+
+ <li>Default indentation is 2 spaces.</li>
+
+ <li>Wrapped parameters have a 4 space indent.</li>
+</ul>
+
+<p>If some parameters are unused, comment out the
+variable name in the function definition:</p>
+
+<pre>// Always have named parameters in interfaces.
+class Shape {
+ public:
+ virtual void Rotate(double radians) = 0;
+};
+
+// Always have named parameters in the declaration.
+class Circle : public Shape {
+ public:
+ virtual void Rotate(double radians);
+};
+
+// Comment out unused named parameters in definitions.
+void Circle::Rotate(double /*radians*/) {}
+</pre>
+
+<pre class="badcode">// Bad - if someone wants to implement later, it's not clear what the
+// variable means.
+void Circle::Rotate(double) {}
+</pre>
+
+</div>
+
+<h3 id="Formatting_Lambda_Expressions">Lambda Expressions</h3>
+
+<div class="summary">
+<p>Format parameters and bodies as for any other function, and capture
+lists like other comma-separated lists.</p>
+</div>
+
+<div class="stylebody">
+<p>For by-reference captures, do not leave a space between the
+ampersand (&) and the variable name.</p>
+<pre>int x = 0;
+auto add_to_x = [&x](int n) { x += n; };
+</pre>
+<p>Short lambdas may be written inline as function arguments.</p>
+<pre>std::set<int> blacklist = {7, 8, 9};
+std::vector<int> digits = {3, 9, 1, 8, 4, 7, 1};
+digits.erase(std::remove_if(digits.begin(), digits.end(), [&blacklist](int i) {
+ return blacklist.find(i) != blacklist.end();
+ }),
+ digits.end());
+</pre>
+
+</div>
+
+<h3 id="Function_Calls">Function Calls</h3>
+
+<div class="summary">
+<p>Either write the call all on a single line, wrap the
+arguments at the parenthesis, or start the arguments on a new
+line indented by four spaces and continue at that 4 space
+indent. In the absence of other considerations, use the
+minimum number of lines, including placing multiple arguments
+on each line where appropriate.</p>
+</div>
+
+<div class="stylebody">
+
+<p>Function calls have the following format:</p>
+<pre>bool retval = DoSomething(argument1, argument2, argument3);
+</pre>
+
+<p>If the arguments do not all fit on one line, they
+should be broken up onto multiple lines, with each
+subsequent line aligned with the first argument. Do not
+add spaces after the open paren or before the close
+paren:</p>
+<pre>bool retval = DoSomething(averyveryveryverylongargument1,
+ argument2, argument3);
+</pre>
+
+<p>Arguments may optionally all be placed on subsequent
+lines with a four space indent:</p>
+<pre>if (...) {
+ ...
+ ...
+ if (...) {
+ DoSomething(
+ argument1, argument2, // 4 space indent
+ argument3, argument4);
+ }
+</pre>
+
+<p>Put multiple arguments on a single line to reduce the
+number of lines necessary for calling a function unless
+there is a specific readability problem. Some find that
+formatting with strictly one argument on each line is
+more readable and simplifies editing of the arguments.
+However, we prioritize for the reader over the ease of
+editing arguments, and most readability problems are
+better addressed with the following techniques.</p>
+
+<p>If having multiple arguments in a single line decreases
+readability due to the complexity or confusing nature of the
+expressions that make up some arguments, try creating
+variables that capture those arguments in a descriptive name:</p>
+<pre>int my_heuristic = scores[x] * y + bases[x];
+bool retval = DoSomething(my_heuristic, x, y, z);
+</pre>
+
+<p>Or put the confusing argument on its own line with
+an explanatory comment:</p>
+<pre>bool retval = DoSomething(scores[x] * y + bases[x], // Score heuristic.
+ x, y, z);
+</pre>
+
+<p>If there is still a case where one argument is
+significantly more readable on its own line, then put it on
+its own line. The decision should be specific to the argument
+which is made more readable rather than a general policy.</p>
+
+<p>Sometimes arguments form a structure that is important
+for readability. In those cases, feel free to format the
+arguments according to that structure:</p>
+<pre>// Transform the widget by a 3x3 matrix.
+my_widget.Transform(x1, x2, x3,
+ y1, y2, y3,
+ z1, z2, z3);
+</pre>
+
+</div>
+
+<h3 id="Braced_Initializer_List_Format">Braced Initializer List Format</h3>
+
+<div class="summary">
+<p>Format a <a href="#Braced_Initializer_List">braced initializer list</a>
+exactly like you would format a function call in its place.</p>
+</div>
+
+<div class="stylebody">
+
+<p>If the braced list follows a name (e.g. a type or
+variable name), format as if the <code>{}</code> were the
+parentheses of a function call with that name. If there
+is no name, assume a zero-length name.</p>
+
+<pre>// Examples of braced init list on a single line.
+return {foo, bar};
+functioncall({foo, bar});
+pair<int, int> p{foo, bar};
+
+// When you have to wrap.
+SomeFunction(
+ {"assume a zero-length name before {"},
+ some_other_function_parameter);
+SomeType variable{
+ some, other, values,
+ {"assume a zero-length name before {"},
+ SomeOtherType{
+ "Very long string requiring the surrounding breaks.",
+ some, other values},
+ SomeOtherType{"Slightly shorter string",
+ some, other, values}};
+SomeType variable{
+ "This is too long to fit all in one line"};
+MyType m = { // Here, you could also break before {.
+ superlongvariablename1,
+ superlongvariablename2,
+ {short, interior, list},
+ {interiorwrappinglist,
+ interiorwrappinglist2}};
+</pre>
+
+</div>
+
+<h3 id="Conditionals">Conditionals</h3>
+
+<div class="summary">
+<p>Prefer no spaces inside parentheses. The <code>if</code>
+and <code>else</code> keywords belong on separate lines.</p>
+</div>
+
+<div class="stylebody">
+
+<p>There are two acceptable formats for a basic
+conditional statement. One includes spaces between the
+parentheses and the condition, and one does not.</p>
+
+<p>The most common form is without spaces. Either is
+fine, but <em>be consistent</em>. If you are modifying a
+file, use the format that is already present. If you are
+writing new code, use the format that the other files in
+that directory or project use. If in doubt and you have
+no personal preference, do not add the spaces.</p>
+
+<pre>if (condition) { // no spaces inside parentheses
+ ... // 2 space indent.
+} else if (...) { // The else goes on the same line as the closing brace.
+ ...
+} else {
+ ...
+}
+</pre>
+
+<p>If you prefer you may add spaces inside the
+parentheses:</p>
+
+<pre>if ( condition ) { // spaces inside parentheses - rare
+ ... // 2 space indent.
+} else { // The else goes on the same line as the closing brace.
+ ...
+}
+</pre>
+
+<p>Note that in all cases you must have a space between
+the <code>if</code> and the open parenthesis. You must
+also have a space between the close parenthesis and the
+curly brace, if you're using one.</p>
+
+<pre class="badcode">if(condition) { // Bad - space missing after IF.
+if (condition){ // Bad - space missing before {.
+if(condition){ // Doubly bad.
+</pre>
+
+<pre>if (condition) { // Good - proper space after IF and before {.
+</pre>
+
+<p>Short conditional statements may be written on one
+line if this enhances readability. You may use this only
+when the line is brief and the statement does not use the
+<code>else</code> clause.</p>
+
+<pre>if (x == kFoo) return new Foo();
+if (x == kBar) return new Bar();
+</pre>
+
+<p>This is not allowed when the if statement has an
+<code>else</code>:</p>
+
+<pre class="badcode">// Not allowed - IF statement on one line when there is an ELSE clause
+if (x) DoThis();
+else DoThat();
+</pre>
+
+<p>In general, curly braces are not required for
+single-line statements, but they are allowed if you like
+them; conditional or loop statements with complex
+conditions or statements may be more readable with curly
+braces. Some
+projects require that an
+<code>if</code> must always always have an accompanying
+brace.</p>
+
+<pre>if (condition)
+ DoSomething(); // 2 space indent.
+
+if (condition) {
+ DoSomething(); // 2 space indent.
+}
+</pre>
+
+<p>However, if one part of an
+<code>if</code>-<code>else</code> statement uses curly
+braces, the other part must too:</p>
+
+<pre class="badcode">// Not allowed - curly on IF but not ELSE
+if (condition) {
+ foo;
+} else
+ bar;
+
+// Not allowed - curly on ELSE but not IF
+if (condition)
+ foo;
+else {
+ bar;
+}
+</pre>
+
+<pre>// Curly braces around both IF and ELSE required because
+// one of the clauses used braces.
+if (condition) {
+ foo;
+} else {
+ bar;
+}
+</pre>
+
+</div>
+
+<h3 id="Loops_and_Switch_Statements">Loops and Switch Statements</h3>
+
+<div class="summary">
+<p>Switch statements may use braces for blocks. Annotate
+non-trivial fall-through between cases.
+Braces are optional for single-statement loops.
+Empty loop bodies should use <code>{}</code> or <code>continue</code>.</p>
+</div>
+
+<div class="stylebody">
+
+<p><code>case</code> blocks in <code>switch</code>
+statements can have curly braces or not, depending on
+your preference. If you do include curly braces they
+should be placed as shown below.</p>
+
+<p>If not conditional on an enumerated value, switch
+statements should always have a <code>default</code> case
+(in the case of an enumerated value, the compiler will
+warn you if any values are not handled). If the default
+case should never execute, simply
+<code>assert</code>:</p>
+
+
+
+<div>
+<pre>switch (var) {
+ case 0: { // 2 space indent
+ ... // 4 space indent
+ break;
+ }
+ case 1: {
+ ...
+ break;
+ }
+ default: {
+ assert(false);
+ }
+}
+</pre>
+</div>
+
+
+
+
+
+<p> Braces are optional for single-statement loops.</p>
+
+<pre>for (int i = 0; i < kSomeNumber; ++i)
+ printf("I love you\n");
+
+for (int i = 0; i < kSomeNumber; ++i) {
+ printf("I take it back\n");
+}
+</pre>
+
+
+<p>Empty loop bodies should use <code>{}</code> or
+<code>continue</code>, but not a single semicolon.</p>
+
+<pre>while (condition) {
+ // Repeat test until it returns false.
+}
+for (int i = 0; i < kSomeNumber; ++i) {} // Good - empty body.
+while (condition) continue; // Good - continue indicates no logic.
+</pre>
+
+<pre class="badcode">while (condition); // Bad - looks like part of do/while loop.
+</pre>
+
+</div>
+
+<h3 id="Pointer_and_Reference_Expressions">Pointer and Reference Expressions</h3>
+
+<div class="summary">
+<p>No spaces around period or arrow. Pointer operators do not
+have trailing spaces.</p>
+</div>
+
+<div class="stylebody">
+
+<p>The following are examples of correctly-formatted
+pointer and reference expressions:</p>
+
+<pre>x = *p;
+p = &x;
+x = r.y;
+x = r->y;
+</pre>
+
+<p>Note that:</p>
+
+<ul>
+ <li>There are no spaces around the period or arrow when
+ accessing a member.</li>
+
+ <li>Pointer operators have no space after the
+ <code>*</code> or <code>&</code>.</li>
+</ul>
+
+<p>When declaring a pointer variable or argument, you may
+place the asterisk adjacent to either the type or to the
+variable name:</p>
+
+<pre>// These are fine, space preceding.
+char *c;
+const string &str;
+
+// These are fine, space following.
+char* c; // but remember to do "char* c, *d, *e, ...;"!
+const string& str;
+</pre>
+
+<pre class="badcode">char * c; // Bad - spaces on both sides of *
+const string & str; // Bad - spaces on both sides of &
+</pre>
+
+<p>You should do this consistently within a single
+file,
+so, when modifying an existing file, use the style in
+that file.</p>
+
+</div>
+
+<h3 id="Boolean_Expressions">Boolean Expressions</h3>
+
+<div class="summary">
+<p>When you have a boolean expression that is longer than the
+<a href="#Line_Length">standard line length</a>, be
+consistent in how you break up the lines.</p>
+</div>
+
+<div class="stylebody">
+
+<p>In this example, the logical AND operator is always at
+the end of the lines:</p>
+
+<pre>if (this_one_thing > this_other_thing &&
+ a_third_thing == a_fourth_thing &&
+ yet_another && last_one) {
+ ...
+}
+</pre>
+
+<p>Note that when the code wraps in this example, both of
+the <code>&&</code> logical AND operators are at
+the end of the line. This is more common in Google code,
+though wrapping all operators at the beginning of the
+line is also allowed. Feel free to insert extra
+parentheses judiciously because they can be very helpful
+in increasing readability when used
+appropriately. Also note that you should always use
+the punctuation operators, such as
+<code>&&</code> and <code>~</code>, rather than
+the word operators, such as <code>and</code> and
+<code>compl</code>.</p>
+
+</div>
+
+<h3 id="Return_Values">Return Values</h3>
+
+<div class="summary">
+<p>Do not needlessly surround the <code>return</code>
+expression with parentheses.</p>
+</div>
+
+<div class="stylebody">
+
+<p>Use parentheses in <code>return expr;</code> only
+where you would use them in <code>x = expr;</code>.</p>
+
+<pre>return result; // No parentheses in the simple case.
+// Parentheses OK to make a complex expression more readable.
+return (some_long_condition &&
+ another_condition);
+</pre>
+
+<pre class="badcode">return (value); // You wouldn't write var = (value);
+return(result); // return is not a function!
+</pre>
+
+</div>
+
+
+
+<h3 id="Variable_and_Array_Initialization">Variable and Array Initialization</h3>
+
+<div class="summary">
+<p>Your choice of <code>=</code>, <code>()</code>, or
+<code>{}</code>.</p>
+</div>
+
+<div class="stylebody">
+
+<p>You may choose between <code>=</code>,
+<code>()</code>, and <code>{}</code>; the following are
+all correct:</p>
+
+<pre>int x = 3;
+int x(3);
+int x{3};
+string name = "Some Name";
+string name("Some Name");
+string name{"Some Name"};
+</pre>
+
+<p>Be careful when using a braced initialization list <code>{...}</code>
+on a type with an <code>std::initializer_list</code> constructor.
+A nonempty <i>braced-init-list</i> prefers the
+<code>std::initializer_list</code> constructor whenever
+possible. Note that empty braces <code>{}</code> are special, and
+will call a default constructor if available. To force the
+non-<code>std::initializer_list</code> constructor, use parentheses
+instead of braces.</p>
+
+<pre>vector<int> v(100, 1); // A vector of 100 1s.
+vector<int> v{100, 1}; // A vector of 100, 1.
+</pre>
+
+<p>Also, the brace form prevents narrowing of integral
+types. This can prevent some types of programming
+errors.</p>
+
+<pre>int pi(3.14); // OK -- pi == 3.
+int pi{3.14}; // Compile error: narrowing conversion.
+</pre>
+
+</div>
+
+<h3 id="Preprocessor_Directives">Preprocessor Directives</h3>
+
+<div class="summary">
+<p>The hash mark that starts a preprocessor directive should
+always be at the beginning of the line.</p>
+</div>
+
+<div class="stylebody">
+
+<p>Even when preprocessor directives are within the body
+of indented code, the directives should start at the
+beginning of the line.</p>
+
+<pre>// Good - directives at beginning of line
+ if (lopsided_score) {
+#if DISASTER_PENDING // Correct -- Starts at beginning of line
+ DropEverything();
+# if NOTIFY // OK but not required -- Spaces after #
+ NotifyClient();
+# endif
+#endif
+ BackToNormal();
+ }
+</pre>
+
+<pre class="badcode">// Bad - indented directives
+ if (lopsided_score) {
+ #if DISASTER_PENDING // Wrong! The "#if" should be at beginning of line
+ DropEverything();
+ #endif // Wrong! Do not indent "#endif"
+ BackToNormal();
+ }
+</pre>
+
+</div>
+
+<h3 id="Class_Format">Class Format</h3>
+
+<div class="summary">
+<p>Sections in <code>public</code>, <code>protected</code> and
+<code>private</code> order, each indented one space.</p>
+</div>
+
+<div class="stylebody">
+
+<p>The basic format for a class declaration (lacking the
+comments, see <a href="#Class_Comments">Class
+Comments</a> for a discussion of what comments are
+needed) is:</p>
+
+<pre>class MyClass : public OtherClass {
+ public: // Note the 1 space indent!
+ MyClass(); // Regular 2 space indent.
+ explicit MyClass(int var);
+ ~MyClass() {}
+
+ void SomeFunction();
+ void SomeFunctionThatDoesNothing() {
+ }
+
+ void set_some_var(int var) { some_var_ = var; }
+ int some_var() const { return some_var_; }
+
+ private:
+ bool SomeInternalFunction();
+
+ int some_var_;
+ int some_other_var_;
+};
+</pre>
+
+<p>Things to note:</p>
+
+<ul>
+ <li>Any base class name should be on the same line as
+ the subclass name, subject to the 80-column limit.</li>
+
+ <li>The <code>public:</code>, <code>protected:</code>,
+ and <code>private:</code> keywords should be indented
+ one space.</li>
+
+ <li>Except for the first instance, these keywords
+ should be preceded by a blank line. This rule is
+ optional in small classes.</li>
+
+ <li>Do not leave a blank line after these
+ keywords.</li>
+
+ <li>The <code>public</code> section should be first,
+ followed by the <code>protected</code> and finally the
+ <code>private</code> section.</li>
+
+ <li>See <a href="#Declaration_Order">Declaration
+ Order</a> for rules on ordering declarations within
+ each of these sections.</li>
+</ul>
+
+</div>
+
+<h3 id="Constructor_Initializer_Lists">Constructor Initializer Lists</h3>
+
+<div class="summary">
+<p>Constructor initializer lists can be all on one line or
+with subsequent lines indented four spaces.</p>
+</div>
+
+<div class="stylebody">
+
+<p>There are two acceptable formats for initializer
+lists:</p>
+
+<pre>// When it all fits on one line:
+MyClass::MyClass(int var) : some_var_(var), some_other_var_(var + 1) {}
+</pre>
+
+<p>or</p>
+
+<pre>// When it requires multiple lines, indent 4 spaces, putting the colon on
+// the first initializer line:
+MyClass::MyClass(int var)
+ : some_var_(var), // 4 space indent
+ some_other_var_(var + 1) { // lined up
+ ...
+ DoSomething();
+ ...
+}
+</pre>
+
+</div>
+
+<h3 id="Namespace_Formatting">Namespace Formatting</h3>
+
+<div class="summary">
+<p>The contents of namespaces are not indented.</p>
+</div>
+
+<div class="stylebody">
+
+<p><a href="#Namespaces">Namespaces</a> do not add an
+extra level of indentation. For example, use:</p>
+
+<pre>namespace {
+
+void foo() { // Correct. No extra indentation within namespace.
+ ...
+}
+
+} // namespace
+</pre>
+
+<p>Do not indent within a namespace:</p>
+
+<pre class="badcode">namespace {
+
+ // Wrong. Indented when it should not be.
+ void foo() {
+ ...
+ }
+
+} // namespace
+</pre>
+
+<p>When declaring nested namespaces, put each namespace
+on its own line.</p>
+
+<pre>namespace foo {
+namespace bar {
+</pre>
+
+</div>
+
+<h3 id="Horizontal_Whitespace">Horizontal Whitespace</h3>
+
+<div class="summary">
+<p>Use of horizontal whitespace depends on location. Never put
+trailing whitespace at the end of a line.</p>
+</div>
+
+<div class="stylebody">
+
+<h4 class="stylepoint_subsection">General</h4>
+
+<pre>void f(bool b) { // Open braces should always have a space before them.
+ ...
+int i = 0; // Semicolons usually have no space before them.
+// Spaces inside braces for braced-init-list are optional. If you use them,
+// put them on both sides!
+int x[] = { 0 };
+int x[] = {0};
+
+// Spaces around the colon in inheritance and initializer lists.
+class Foo : public Bar {
+ public:
+ // For inline function implementations, put spaces between the braces
+ // and the implementation itself.
+ Foo(int b) : Bar(), baz_(b) {} // No spaces inside empty braces.
+ void Reset() { baz_ = 0; } // Spaces separating braces from implementation.
+ ...
+</pre>
+
+<p>Adding trailing whitespace can cause extra work for
+others editing the same file, when they merge, as can
+removing existing trailing whitespace. So: Don't
+introduce trailing whitespace. Remove it if you're
+already changing that line, or do it in a separate
+clean-up
+operation (preferably when no-one
+else is working on the file).</p>
+
+<h4 class="stylepoint_subsection">Loops and Conditionals</h4>
+
+<pre>if (b) { // Space after the keyword in conditions and loops.
+} else { // Spaces around else.
+}
+while (test) {} // There is usually no space inside parentheses.
+switch (i) {
+for (int i = 0; i < 5; ++i) {
+// Loops and conditions may have spaces inside parentheses, but this
+// is rare. Be consistent.
+switch ( i ) {
+if ( test ) {
+for ( int i = 0; i < 5; ++i ) {
+// For loops always have a space after the semicolon. They may have a space
+// before the semicolon, but this is rare.
+for ( ; i < 5 ; ++i) {
+ ...
+
+// Range-based for loops always have a space before and after the colon.
+for (auto x : counts) {
+ ...
+}
+switch (i) {
+ case 1: // No space before colon in a switch case.
+ ...
+ case 2: break; // Use a space after a colon if there's code after it.
+</pre>
+
+<h4 class="stylepoint_subsection">Operators</h4>
+
+<pre>// Assignment operators always have spaces around them.
+x = 0;
+
+// Other binary operators usually have spaces around them, but it's
+// OK to remove spaces around factors. Parentheses should have no
+// internal padding.
+v = w * x + y / z;
+v = w*x + y/z;
+v = w * (x + z);
+
+// No spaces separating unary operators and their arguments.
+x = -5;
+++x;
+if (x && !y)
+ ...
+</pre>
+
+<h4 class="stylepoint_subsection">Templates and Casts</h4>
+
+<pre>// No spaces inside the angle brackets (< and >), before
+// <, or between >( in a cast
+vector<string> x;
+y = static_cast<char*>(x);
+
+// Spaces between type and pointer are OK, but be consistent.
+vector<char *> x;
+set<list<string>> x; // Permitted in C++11 code.
+set<list<string> > x; // C++03 required a space in > >.
+
+// You may optionally use symmetric spacing in < <.
+set< list<string> > x;
+</pre>
+
+</div>
+
+<h3 id="Vertical_Whitespace">Vertical Whitespace</h3>
+
+<div class="summary">
+<p>Minimize use of vertical whitespace.</p>
+</div>
+
+<div class="stylebody">
+
+<p>This is more a principle than a rule: don't use blank
+lines when you don't have to. In particular, don't put
+more than one or two blank lines between functions,
+resist starting functions with a blank line, don't end
+functions with a blank line, and be discriminating with
+your use of blank lines inside functions.</p>
+
+<p>The basic principle is: The more code that fits on one
+screen, the easier it is to follow and understand the
+control flow of the program. Of course, readability can
+suffer from code being too dense as well as too spread
+out, so use your judgement. But in general, minimize use
+of vertical whitespace.</p>
+
+<p>Some rules of thumb to help when blank lines may be
+useful:</p>
+
+<ul>
+ <li>Blank lines at the beginning or end of a function
+ very rarely help readability.</li>
+
+ <li>Blank lines inside a chain of if-else blocks may
+ well help readability.</li>
+</ul>
+
+</div>
+
+<h2 id="Exceptions_to_the_Rules">Exceptions to the Rules</h2>
+
+<p>The coding conventions described above are mandatory.
+However, like all good rules, these sometimes have exceptions,
+which we discuss here.</p>
+
+
+
+<div>
+<h3 id="Existing_Non-conformant_Code">Existing Non-conformant Code</h3>
+
+<div class="summary">
+<p>You may diverge from the rules when dealing with code that
+does not conform to this style guide.</p>
+</div>
+
+<div class="stylebody">
+
+<p>If you find yourself modifying code that was written
+to specifications other than those presented by this
+guide, you may have to diverge from these rules in order
+to stay consistent with the local conventions in that
+code. If you are in doubt about how to do this, ask the
+original author or the person currently responsible for
+the code. Remember that <em>consistency</em> includes
+local consistency, too.</p>
+
+</div>
+</div>
+
+
+<h2 class="ignoreLink">Parting Words</h2>
+
+<p>Use common sense and <em>BE CONSISTENT</em>.</p>
+
+<p>If you are editing code, take a few minutes to look at the
+code around you and determine its style. If they use spaces
+around their <code>if</code> clauses, you should, too. If their
+comments have little boxes of stars around them, make your
+comments have little boxes of stars around them too.</p>
+
+<p>The point of having style guidelines is to have a common
+vocabulary of coding so people can concentrate on what you are
+saying, rather than on how you are saying it. We present global
+style rules here so people know the vocabulary. But local style
+is also important. If code you add to a file looks drastically
+different from the existing code around it, the discontinuity
+throws readers out of their rhythm when they go to read it. Try
+to avoid this.</p>
+
+
+
+<p>OK, enough writing about writing code; the code itself is much
+more interesting. Have fun!</p>
+
+<hr>
+
+<p style="text-align:right; font-style:italic;">Revision 4.45</p>
+
+</div>
+</body></html>