Difference between revisions of "Coding Style"

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(Clean this up a bit until (if) the new Coding Style gets published.)
(File Structure: link to Documentation Guidelines for Doxygen format)
 
(21 intermediate revisions by 7 users not shown)
Line 1: Line 1:
The ReactOS Project currently enforces very few rules for coding style.
+
This article describes general coding style guidelines, which should be used for new ReactOS code. These guidelines apply exclusively to C and C++ source files. The Members of ReactOS agreed on this document in the October 2013 meeting.
  
== 3rd party code ==
+
As much existing ReactOS code as possible should be converted to this style unless there are reasons against doing this (like if the code is going to be rewritten from scratch in the near future). See [[#Notes on reformatting existing code|Notes on reformatting existing code]] for more details.
ReactOS uses code from other projects (e.g., Wine). In these instances the following guidelines do not apply and the existing style should be used. This allows easier syncing of future changes.
 
  
== Formatting ==
+
Code synchronized with other sources (like Wine) must not be rewritten. [https://github.com/reactos/reactos/blob/master/media/doc/README.WINE README.WINE], [https://github.com/reactos/reactos/blob/master/media/doc/README.FSD README.FSD] and [https://github.com/reactos/reactos/blob/master/media/doc/3rd%20Party%20Files.txt 3rd Party Files.txt] files can be used for tracking synchronized files.
Formatting should be done separately from code changes. Patches or commits that only change formatting should indicate so (e.g., "Formatting, no code changes", [FORMATTING] label).
 
  
=== Indentation ===
+
== File Structure ==
One level of indentation is 4 columns. Spaces must be used.
+
<ol>
 +
<li>Every ReactOS source code file should include a file header like this:
 +
<syntaxhighlight lang="c">
 +
/*
 +
* PROJECT:    ReactOS Kernel
 +
* LICENSE:    GPL-2.0-or-later (https://spdx.org/licenses/GPL-2.0-or-later)
 +
* PURPOSE:    Does cool things like ...
 +
* COPYRIGHT:  Copyright 2017 Arno Nymous (abc@mailaddress.com)
 +
*              Copyright 2017 Mike Blablabla (mike@blabla.com)
 +
*/
 +
</syntaxhighlight>
 +
 
 +
Please use SPDX license identifiers available at https://spdx.org/licenses.
 +
This makes our source file parseable by licensing tools!
 +
 
 +
You should add yourself to the <tt>COPYRIGHT</tt> section of a file if you did a major contribution to it and could take responsibility for the whole file or a part of it.
 +
 
 +
<tt>FILE</tt> line of the old header should be removed.
 +
</li>
 +
 
 +
<li>[https://doxygen.reactos.org/ Doxygen] documentation generator is used for ReactOS codebase, so use a proper header for functions, see [[Documentation Guidelines#API Documentation|API Documentation]] for details.</li>
 +
</ol>
  
=== Braces ===
+
== Indentation ==
Braces must be placed on their own lines. They must be at the same indentation level as the previous statement. Braces are optional if only one statement is enclosed in it, excepting when a comment is also present.
+
<ol>
 +
<li>Indent with 4 spaces, don’t use tabs!</li>
 +
<li><p>Indent both a case label and the case statement of a switch statement.</p>
 +
 
 +
'''Right:'''
 +
<syntaxhighlight lang="c">
 +
switch (Condition)
 +
{
 +
    case 1:
 +
        DoSomething();
 +
        break;
 +
}
 +
</syntaxhighlight>
  
Incorrect:
+
'''Wrong:'''
 
<syntaxhighlight lang="c">
 
<syntaxhighlight lang="c">
if (foo()) {
+
switch (Condition)
    bar();
+
{
 +
case 1:
 +
    DoSomething();
 +
    break;
 
}
 
}
 +
</syntaxhighlight>
 +
</li>
 +
</ol>
 +
 +
== Spacing ==
 +
<ol>
 +
<li>Do not use spaces around unary operators.<br />
 +
'''Right:''' <code>i++;</code><br />
 +
'''Wrong:''' <code>i ++;</code>
 +
</li>
 +
 +
<li>Place spaces around binary and ternary operators.<br />
 +
'''Right:''' <code>a = b + c;</code><br />
 +
'''Wrong:''' <code>a=b+c;</code>
 +
</li>
 +
 +
<li><p>Do not place spaces before comma and semicolon.</p>
  
if (foo())
+
'''Right:'''
    /* Comment */
+
<syntaxhighlight lang="c">
    bar();
+
for (int i = 0; i < 5; i++)
 +
    DoSomething();
 +
 
 +
func1(a, b);
 
</syntaxhighlight>
 
</syntaxhighlight>
Correct:
+
 
 +
'''Wrong:'''
 
<syntaxhighlight lang="c">
 
<syntaxhighlight lang="c">
if (foo())
+
for (int i = 0 ; i < 5 ; i++)
 +
    DoSomething();
 +
 
 +
func1(a , b) ;
 +
</syntaxhighlight>
 +
</li>
 +
 
 +
<li><p>Place spaces between control statements and their parentheses.</p>
 +
 
 +
'''Right:'''
 +
<syntaxhighlight lang="c">
 +
if (Condition)
 +
    DoSomething();
 +
</syntaxhighlight>
 +
 
 +
'''Wrong:'''
 +
<syntaxhighlight lang="c">
 +
if(Condition)
 +
    DoSomething();
 +
</syntaxhighlight>
 +
</li>
 +
 
 +
<li><p>Do not place spaces between a function and its parentheses, or between a parenthesis and its content.</p>
 +
 
 +
'''Right:'''
 +
<syntaxhighlight lang="c">
 +
func(a, b);
 +
</syntaxhighlight>
 +
 
 +
'''Wrong:'''
 +
<syntaxhighlight lang="c">
 +
func (a, b);
 +
func( a, b );
 +
</syntaxhighlight>
 +
</li>
 +
</ol>
 +
 
 +
== Line breaking ==
 +
<ol>
 +
<li><p>Each statement should get its own line.</p>
 +
 
 +
'''Right:'''
 +
<syntaxhighlight lang="c">
 +
x++;
 +
y++;
 +
 
 +
if (Condition)
 +
    DoSomething();
 +
</syntaxhighlight>
 +
 
 +
'''Wrong:'''
 +
<syntaxhighlight lang="c">
 +
x++; y++;
 +
 
 +
if (Condition) DoSomething();
 +
</syntaxhighlight>
 +
</li>
 +
</ol>
 +
 
 +
== Braces ==
 +
<ol>
 +
<li>Always put braces (''{'' and ''}'') on their own lines.</li>
 +
<li><p>One-line control clauses may use braces, but this is not a requirement. An exception are one-line control clauses including additional comments.</p>
 +
 
 +
'''Right:'''
 +
<syntaxhighlight lang="c">
 +
if (Condition)
 +
    DoSomething();
 +
 
 +
if (Condition)
 
{
 
{
     bar();
+
     DoSomething();
 
}
 
}
  
 +
if (Condition)
 +
{
 +
    // This is a comment
 +
    DoSomething();
 +
}
  
if (foo())
+
if (Condition)
     bar();
+
    DoSomething();
 +
else
 +
    DoSomethingElse();
 +
 
 +
if (Condition)
 +
{
 +
     DoSomething();
 +
}
 +
else
 +
{
 +
    DoSomethingElse();
 +
    YetAnother();
 +
}
 +
</syntaxhighlight>
 +
 
 +
'''Wrong:'''
 +
<syntaxhighlight lang="c">
 +
if (Condition) {
 +
    DoSomething();
 +
}
  
 +
if (Condition)
 +
    // This is a comment
 +
    DoSomething();
  
if (foo())
+
if (Condition)
 +
    DoSomething();
 +
else
 
{
 
{
     /* Comment */
+
     DoSomethingElse();
     bar();
+
     YetAnother();
 
}
 
}
 
</syntaxhighlight>
 
</syntaxhighlight>
 +
</li>
 +
</ol>
  
=== Long lines ===
+
== Control structures ==
80 columns should be used as a guide for line length.
+
<ol>
 +
<li>Don’t use inverse logic in control clauses.<br />
 +
'''Right:''' <code>if (i == 1)</code><br />
 +
'''Wrong:''' <code>if (1 == i)</code>
 +
</li>
  
* When a line with function call is less than 80 chars long, params should be written on the same line
+
<li><p>Avoid too many levels of cascaded control structures. Prefer a “linear style” over a “tree style”. Use <code>goto</code> when it helps to make the code cleaner (e.g. for cleanup paths).</p>
* When a line with function call is more than 80 chars long (because calling func has many params), it maybe wise to write params as column, writing comments for each param (when it is needed)
 
  
== File structure ==
+
'''Right:'''
The usual source code file consists of the following parts (some sections can be omitted if they are empty):
 
* The header (an example)
 
 
<syntaxhighlight lang="c">
 
<syntaxhighlight lang="c">
/*
+
if (!func1())
  * PROJECT:        ReactOS Kernel
+
    return;
  * LICENSE:        GPL - See COPYING in the top level directory
+
 
  * FILE:            ntoskrnl/ob/namespce.c
+
i = func2();
  * PURPOSE:        Manages all functions related to the Object Manager name-
+
if (i == 0)
  *                  space, such as finding objects or querying their names.
+
    return;
  * PROGRAMMERS:    Alex Ionescu (alex.ionescu@reactos.org)
+
 
  *                  Eric Kohl
+
j = func3();
  *                  Thomas Weidenmueller (w3seek@reactos.org)
+
if (j == 1)
  */
+
    return;
 +
 
</syntaxhighlight>
 
</syntaxhighlight>
* Includes section, which has all #include statements, and vital defines (like #define NDEBUG)
+
 
 +
'''Wrong:'''
 
<syntaxhighlight lang="c">
 
<syntaxhighlight lang="c">
/* INCLUDES ******************************************************************/
+
if (func1())
 +
{
 +
    i = func2();
 +
    if (func2())
 +
    {
 +
        j = func3();
 +
        if (func3())
 +
        {
 +
            …
 +
        }
 +
    }
 +
}
 
</syntaxhighlight>
 
</syntaxhighlight>
* Defines section, for per-file defines
+
</li>
 +
</ol>
 +
 
 +
== Naming ==
 +
<ol>
 +
<li><p>Capitalize names of variables and functions.<br />
 +
[[Hungarian Notation]] may be used when developing for Win32, but it is not required. If you don’t use it, the first letter of a name must be a capital too (no camelCase). Do not use underscores as separators either.</p>
 +
 
 +
'''Right:'''
 
<syntaxhighlight lang="c">
 
<syntaxhighlight lang="c">
/* DEFINES *******************************************************************/
+
PLIST_ENTRY FirstEntry;
 +
VOID NTAPI IopDeleteIoCompletion(PVOID ObjectBody);
 +
PWSTR pwszTest;
 
</syntaxhighlight>
 
</syntaxhighlight>
* Private (not exported, or used only within the scope of this file) functions
+
 
 +
'''Wrong:'''
 
<syntaxhighlight lang="c">
 
<syntaxhighlight lang="c">
/* PRIVATE FUNCTIONS ******************************************************/
+
PLIST_ENTRY first_entry;
 +
VOID NTAPI iop_delete_io_completion(PVOID objectBody);
 +
PWSTR pwsztest;
 
</syntaxhighlight>
 
</syntaxhighlight>
* Public functions (if it's a DLL, or a driver)
+
</li>
 +
 
 +
<li>Avoid abbreviating function and variable names, use descriptive verbs where possible.</li>
 +
<li><p>Precede boolean values with meaningful verbs like "is" and "did" if possible and if it fits the usage.</p>
 +
 
 +
'''Right:'''
 
<syntaxhighlight lang="c">
 
<syntaxhighlight lang="c">
/* PUBLIC FUNCTIONS **********************************************************/
+
BOOLEAN IsValid;
 +
BOOLEAN DidSendData;
 
</syntaxhighlight>
 
</syntaxhighlight>
* Or just this way, if it's a standalone app
+
 
 +
'''Wrong:'''
 
<syntaxhighlight lang="c">
 
<syntaxhighlight lang="c">
/* FUNCTIONS *****************************************************************/
+
BOOLEAN Valid;
 +
BOOLEAN SentData;
 
</syntaxhighlight>
 
</syntaxhighlight>
* [OPTIONAL?]File ends with
+
</li>
 +
</ol>
 +
 
 +
== Commenting ==
 +
<ol>
 +
<li><p>Avoid line-wasting comments, which could fit into a single line.</p>
 +
 
 +
'''Right:'''
 
<syntaxhighlight lang="c">
 
<syntaxhighlight lang="c">
/* EOF */<NewLineCharacterOnYourPlatform>
+
// This is a one-line comment
 +
 
 +
/* This is a C-style comment */
 +
 
 +
//
 +
// This is a comment over multiple lines.
 +
// We don’t define any strict rules for it.
 +
//
 
</syntaxhighlight>
 
</syntaxhighlight>
  
== The Rules ==
+
'''Wrong:'''
Example of standard API header, please don't make up your own until really necessary:
 
 
<syntaxhighlight lang="c">
 
<syntaxhighlight lang="c">
/*++
+
//
* @name SomeAPI
+
// This comment wastes two lines
* @implemented NT4
+
//
*
 
* Do nothing for 500ms.
 
*
 
* @param SomeParameter
 
*        Description of the parameter. Wrapped to more lines on ~70th
 
*        column.
 
*
 
* @param YetAnotherParameter
 
*        Bleh, bleh :)
 
*
 
* @return STATUS_SUCCESS in case of success, STATUS_UNSUCCESSFUL
 
*        othwerwise.
 
*
 
* @remarks Must be called at IRQL == DISPATCH_LEVEL
 
*
 
*--*/
 
NTSTATUS
 
NTAPI
 
SomeAPI(...)
 
 
</syntaxhighlight>
 
</syntaxhighlight>
 +
</li>
 +
</ol>
 +
 +
== Null, false and 0 ==
 +
<ol>
 +
<li>The null pointer should be written as <code>NULL</code>.<br />
 +
In the rare case that your environment recommends a different null pointer (e.g. C++11 <code>nullptr</code>), you may use this one of course. Just don’t use the value <code>0</code>.</li>
 +
<li>Win32/NT Boolean values should be written as <code>TRUE</code> and <code>FALSE</code>.<br />
 +
In the rare case that you use C/C++ <code>bool</code> variables, you should write them as <code>true</code> and <code>false</code>.</li>
 +
<li>When you need to terminate ANSI or OEM string, or check for its terminator, use <code>ANSI_NULL</code>. If the string is Unicode or Wide string, use <code>UNICODE_NULL</code>.
 +
</ol>
 +
 +
== Notes on reformatting existing code ==
 +
* Never totally reformat a file and put a code change into it. Do this in separate commits.
 +
* If a commit only consists of formatting changes, say this clearly in the commit message by preceding it with ''[FORMATTING]''.
  
== Astyle for kernel code ==
+
== Using an automatic code style tool ==
astyle -b -c -y --style=ansi --mode=c $FILE
+
TO BE ADDED BY [[User:Zefklop]]
  
== Text Editors ==
+
== Points deliberately left out ==
* Notepad (GvG), problem is tab always == 8 spaces
+
Additional ideas were suggested during the discussion of this document, but a consensus couldn't be reached on them. Therefore we refrain from enforcing any rules on these points:
* Syn (w3seek), problem is tabs again
+
* TO BE ADDED BY [[User:Hbelusca]]
* Eclipse (w3seek), like the same
 
* Ultraedit on windows (hpoussin), indenting blank lines
 
* vi on unix (tinus)
 
* Crimson Editor (Ged) no known problems
 
* VS 2k3 (Brandon), Don't know any problems.  I like using tabs.  Willing to change if need be.
 
  
== See Also ==
+
== See also ==
* [[Programming Guidelines]]
+
* [[Kernel Coding Style]]
 
* [[GNU Indent]]
 
* [[GNU Indent]]
  
 
+
[[Category:Development]]
 
[[Category:Documentation]]
 
[[Category:Documentation]]
[[Category:Quality]]
+
[[Category:Tutorial]]

Latest revision as of 12:47, 9 July 2019

This article describes general coding style guidelines, which should be used for new ReactOS code. These guidelines apply exclusively to C and C++ source files. The Members of ReactOS agreed on this document in the October 2013 meeting.

As much existing ReactOS code as possible should be converted to this style unless there are reasons against doing this (like if the code is going to be rewritten from scratch in the near future). See Notes on reformatting existing code for more details.

Code synchronized with other sources (like Wine) must not be rewritten. README.WINE, README.FSD and 3rd Party Files.txt files can be used for tracking synchronized files.

File Structure

  1. Every ReactOS source code file should include a file header like this:
    /*
     * PROJECT:     ReactOS Kernel
     * LICENSE:     GPL-2.0-or-later (https://spdx.org/licenses/GPL-2.0-or-later)
     * PURPOSE:     Does cool things like ...
     * COPYRIGHT:   Copyright 2017 Arno Nymous (abc@mailaddress.com)
     *              Copyright 2017 Mike Blablabla (mike@blabla.com)
     */
    

    Please use SPDX license identifiers available at https://spdx.org/licenses. This makes our source file parseable by licensing tools!

    You should add yourself to the COPYRIGHT section of a file if you did a major contribution to it and could take responsibility for the whole file or a part of it.

    FILE line of the old header should be removed.

  2. Doxygen documentation generator is used for ReactOS codebase, so use a proper header for functions, see API Documentation for details.

Indentation

  1. Indent with 4 spaces, don’t use tabs!
  2. Indent both a case label and the case statement of a switch statement.

    Right:

    switch (Condition)
    {
        case 1:
            DoSomething();
            break;
    }
    

    Wrong:

    switch (Condition)
    {
    case 1:
         DoSomething();
         break;
    }
    

Spacing

  1. Do not use spaces around unary operators.
    Right: i++;
    Wrong: i ++;
  2. Place spaces around binary and ternary operators.
    Right: a = b + c;
    Wrong: a=b+c;
  3. Do not place spaces before comma and semicolon.

    Right:

    for (int i = 0; i < 5; i++)
        DoSomething();
    
    func1(a, b);
    

    Wrong:

    for (int i = 0 ; i < 5 ; i++)
        DoSomething();
    
    func1(a , b) ;
    
  4. Place spaces between control statements and their parentheses.

    Right:

    if (Condition)
        DoSomething();
    

    Wrong:

    if(Condition)
        DoSomething();
    
  5. Do not place spaces between a function and its parentheses, or between a parenthesis and its content.

    Right:

    func(a, b);
    

    Wrong:

    func (a, b);
    func( a, b );
    

Line breaking

  1. Each statement should get its own line.

    Right:

    x++;
    y++;
    
    if (Condition)
        DoSomething();
    

    Wrong:

    x++; y++;
    
    if (Condition) DoSomething();
    

Braces

  1. Always put braces ({ and }) on their own lines.
  2. One-line control clauses may use braces, but this is not a requirement. An exception are one-line control clauses including additional comments.

    Right:

    if (Condition)
        DoSomething();
    
    if (Condition)
    {
        DoSomething();
    }
    
    if (Condition)
    {
        // This is a comment
        DoSomething();
    }
    
    if (Condition)
        DoSomething();
    else
        DoSomethingElse();
    
    if (Condition)
    {
        DoSomething();
    }
    else
    {
        DoSomethingElse();
        YetAnother();
    }
    

    Wrong:

    if (Condition) {
        DoSomething();
    }
    
    if (Condition)
        // This is a comment
        DoSomething();
    
    if (Condition)
        DoSomething();
    else
    {
        DoSomethingElse();
        YetAnother();
    }
    

Control structures

  1. Don’t use inverse logic in control clauses.
    Right: if (i == 1)
    Wrong: if (1 == i)
  2. Avoid too many levels of cascaded control structures. Prefer a “linear style” over a “tree style”. Use goto when it helps to make the code cleaner (e.g. for cleanup paths).

    Right:

    if (!func1())
        return;
    
    i = func2();
    if (i == 0)
        return;
    
    j = func3();
    if (j == 1)
        return;
    
    

    Wrong:

    if (func1())
    {
        i = func2();
        if (func2())
        {
            j = func3();
            if (func3())
            {
                
            }
        }
    }
    

Naming

  1. Capitalize names of variables and functions.
    Hungarian Notation may be used when developing for Win32, but it is not required. If you don’t use it, the first letter of a name must be a capital too (no camelCase). Do not use underscores as separators either.

    Right:

    PLIST_ENTRY FirstEntry;
    VOID NTAPI IopDeleteIoCompletion(PVOID ObjectBody);
    PWSTR pwszTest;
    

    Wrong:

    PLIST_ENTRY first_entry;
    VOID NTAPI iop_delete_io_completion(PVOID objectBody);
    PWSTR pwsztest;
    
  2. Avoid abbreviating function and variable names, use descriptive verbs where possible.
  3. Precede boolean values with meaningful verbs like "is" and "did" if possible and if it fits the usage.

    Right:

    BOOLEAN IsValid;
    BOOLEAN DidSendData;
    

    Wrong:

    BOOLEAN Valid;
    BOOLEAN SentData;
    

Commenting

  1. Avoid line-wasting comments, which could fit into a single line.

    Right:

    // This is a one-line comment
    
    /* This is a C-style comment */
    
    //
    // This is a comment over multiple lines.
    // We don’t define any strict rules for it.
    //
    

    Wrong:

    //
    // This comment wastes two lines
    //
    

Null, false and 0

  1. The null pointer should be written as NULL.
    In the rare case that your environment recommends a different null pointer (e.g. C++11 nullptr), you may use this one of course. Just don’t use the value 0.
  2. Win32/NT Boolean values should be written as TRUE and FALSE.
    In the rare case that you use C/C++ bool variables, you should write them as true and false.
  3. When you need to terminate ANSI or OEM string, or check for its terminator, use ANSI_NULL. If the string is Unicode or Wide string, use UNICODE_NULL.

Notes on reformatting existing code

  • Never totally reformat a file and put a code change into it. Do this in separate commits.
  • If a commit only consists of formatting changes, say this clearly in the commit message by preceding it with [FORMATTING].

Using an automatic code style tool

TO BE ADDED BY User:Zefklop

Points deliberately left out

Additional ideas were suggested during the discussion of this document, but a consensus couldn't be reached on them. Therefore we refrain from enforcing any rules on these points:

See also