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Nächste Überarbeitung 		Vorhergehende Überarbeitung
private:codingstyle [2013/04/18 22:44]
Patrick Wacker angelegt 		private:codingstyle [2013/04/19 15:07] (aktuell)
Patrick Wacker dies und das
Zeile 1: Zeile 1:
 +
 +
 +//80 characters line - the + is at character 74
 +
 +--------------------------------------------------------------------------+-----
 +
 +//the following line starts with a tabulator
 +
 + < tab!
 +
 +
 +====== Version 1 ======
 +short explanation
 +################################################################################​
 +
 ====== Coding Style ====== ====== Coding Style ======
  
-This documents ​discripes ​the coding style I prefer in the most cases+==== Introduction ==== 
 + 
 +This documents ​describes ​the coding style I prefer in the most cases
 and most other situations as well. and most other situations as well.
  
 In general I like the coding style of the linux kernel and most parts In general I like the coding style of the linux kernel and most parts
 of the descriptions made here are identical to the linux kernel. of the descriptions made here are identical to the linux kernel.
 +
 +=== Editing this document ===
 +
 +The text for this document is written with the syntax that dokuwiki supports.
 +See https://​www.dokuwiki.org for more details.
 +
 +But this document should be easily readable as plain text as well. So do not
 +use any fancy looking html outputs.
 +
 +Only the following dokuwiki syntax options should be used:
 +
 +<​code>​
 +**text** for bold text
 +__text__ for underlined text
 +==== header ==== for chapters
 +</​code>​
 +
 +each code example must be indented with a tabulator! (not spaces!)\\ ​
 +[This is automatically displayed as code examples!]
 +
 +
 +
 +
 +
 +
 +====== Version 2 ======
 +mostly from: http://​techbase.kde.org/​Policies/​Kdelibs_Coding_Style
 +################################################################################​
 +
 +
 +===== Coding style =====
 +
 +This documents describes the coding style I prefer. Coding style is very
 +personal, and I won't force my views on anybody, but this is what goes for
 +anything that I have to be able to maintain, and I'd prefer it for most
 +other things too.
 +
 +Please at least consider the points made here.
 +
 +
 +==== Indentation ====
 +
 +  * use tabs for indentation
 +  * tabs are 8 characters, and thus indentations are also 8 characters.
 +
 +==== Variable declaration ====
 +
 +  * Each new word in a variable name starts with a capital letter\\ (so-called camelCase)
 +  * Avoid abbreviations
 +  * Take usefull names. No short names, except:
 +    * singe character variable names can denote counters and temporary\\ variables whose purpose is obvious
 +  * Variables and functions start with a lowercase letter
 +
 +==== Whitespace ====
 +
 +  * Use blank lines to group statements
 +  * Use only one empty line
 +  * Use one space after each keyword
 +  * For pointers or references, use a single space before '​*'​ or '&',​ but not after
 +  * No space after a cast
 +
 +==== Braces ====
 +
 +As a base rule, the left curly brace goes in the same line as the start of the statement.
 +
 +Example:
 + // wrong
 + if (true)
 + {
 + }
 +
 + // correct
 + if (true) {
 + }
 +
 +Exception: Function implemnetations,​ class, struct and namespace declarations always have the opening brace in the start of a line.
 +
 +Example:
 + void debug(int i)
 + {
 + qDebug("​foo:​ %i", i);
 + }
 +
 + class Debug
 + {
 + };
 +
 +
 +Do not unnecessarily use braces where a single statement will do.
 +
 + if (condition)
 + action();
 +
 +and
 +
 + if (condition)
 + do_this();​
 + else
 + do_that();​
 +
 +This does not apply if one branch of a conditional statement is a 
 +single statement. Use braces in both branches.
 +
 + if (condition) {
 + do_this();​
 + do_that();​
 + } else {
 + otherwise();​
 + }
 +
 +
 +==== Switch statements ====
 +
 +Case labels are on the same column as the switch
 +
 + switch (myEnum) {
 + case Value1:
 + doSomething();​
 + break;
 + case Value2:
 + doSomethingElse();​
 + /* fall through */
 + default:
 + defaultHandling();​
 + break;
 + }
 +
 +==== Line breaks ====
 +
 +Try to keep lines shorter than 80 characters, insert line breaks as necessary.
 +
 +Long strings are as well broken into shorter strings. The exception to this 
 +is where exceeding 80 columns significantly increases readability and does 
 +not hide information.
 +
 +
 +
 +
 +
 +====== Version 3 ======
 +mostly from linux kernel
 +################################################################################​
 +
 +
 +===== Coding style =====
 +
 +This documents describes the coding style I prefer. Coding style is very
 +personal, and I won't force my views on anybody, but this is what goes for
 +anything that I have to be able to maintain, and I'd prefer it for most
 +other things too.
 +
 +Please at least consider the points made here.
 +
 +
 +==== Indentation ====
 +
 +Tabs are 8 characters, and thus indentations are also 8 characters.
 +
 +Rationale: The whole idea behind indentation is to clearly define where
 +a block of control starts and ends. Especially when you've been looking
 +at your screen for many hours, you'll find it a lot easier to see how 
 +the indentation works if you have large indentations.
 +
 +Now, some people will claim that having 8-character indentations makes
 +the code move too far to the right, and makes it hard to read on a
 +80-character terminal screen. ​ The answer to that is that if you need
 +more than 3 levels of indentation,​ you're screwed anyway, and should fix
 +your program.
 +
 +In short, 8-char indents make things easier to read, and have the added
 +benefit of warning you when you're nesting your functions too deep.
 +Heed that warning.
 +
 +The preferred way to ease multiple indentation levels in a switch statement is
 +to align the "​switch"​ and its subordinate "​case"​ labels in the same column
 +instead of "​double-indenting"​ the "​case"​ labels. ​ E.g.:
 +
 + switch (suffix) {
 + case '​G':​
 + case '​g':​
 + mem <<= 30;
 + break;
 + case '​M':​
 + case '​m':​
 + mem <<= 20;
 + break;
 + case '​K':​
 + case '​k':​
 + mem <<= 10;
 + /* fall through */
 + default:
 + break;
 + }
 +
 +
 +Don't put multiple statements on a single line unless you have
 +something to hide:
 +
 + if (condition) do_this;
 +   do_something_everytime;​
 +
 +Don't put multiple assignments on a single line either. Avoid 
 +tricky expressions.
 +
 +Outside of comments and documentation,​ spaces are never used for
 +indentation,​ and the above example is deliberately broken.
 +
 +Get a decent editor and don't leave whitespace at the end of lines.
 +
 +
 +
 +
 +
 +==== Breaking long lines and strings ====
 +
 +Coding style is all about readability and maintainability using commonly
 +available tools.
 +
 +The limit on the length of lines is 80 columns but this is not a strong
 +limit.
 +
 +Statements longer than 80 columns should be broken into sensible chunks.
 +Descendants are always substantially shorter than the parent and are placed
 +aligned to the opening brace of the previous line. The same applies to 
 +function headers with a long argument list. Long strings are as well broken
 +into shorter strings. The exception to this is where exceeding 80 columns
 +significantly increases readability and does not hide information.
 +
 + void fun(int a, int b, int c)
 + {
 + if (condition)
 + qWarning("​This is a long Warning message with 3 "
 + "​parameters a: %u b: %u and c: %u",
 + a, b, c);
 + else
 + next_statement;​
 + }
 +
 +
 +
 +
 +==== Placing Braces and Spaces ====
 +
 +The other issue that always comes up in C styling is the placement of
 +braces. Unlike the indent size, there are few technical reasons to
 +choose one placement strategy over the other, but the preferred way, as
 +shown to us by the prophets Kernighan and Ritchie, is to put the opening
 +brace last on the line, and put the closing brace first, thusly:
 +
 + if (x is true) {
 + we do y
 + }
 +
 +This applies to all non-function statement blocks (if, switch, for,
 +while, do).  E.g.:
 +
 + switch (action) {
 + case ADD:
 + return "​add";​
 + case REMOVE:
 + return "​remove";​
 + case CHANGE:
 + return "​change";​
 + default:
 + return NULL;
 + }
 +
 +However, there is one special case, namely functions: they have the
 +opening brace at the beginning of the next line, thus:
 +
 + int function(int x)
 + {
 + body of function
 + }
 +
 +Heretic people all over the world have claimed that this inconsistency
 +is ...  well ...  inconsistent,​ but all right-thinking people know that
 +(a) K&R are __right__ and (b) K&R are right. Besides, functions are
 +special anyway (you can't nest them in C/C++).
 +
 +Note that the closing brace is empty on a line of its own, __except__ in
 +the cases where it is followed by a continuation of the same statement,
 +ie a "​while"​ in a do-statement or an "​else"​ in an if-statement,​ like
 +this:
 +
 + do {
 + body of do-loop
 + } while (condition);​
 +
 +and
 +
 + if (x == y) {
 + ..
 + } else if (x > y) {
 + ...
 + } else {
 + ....
 + }
 +
 +Rationale: K&R.
 +
 +Also, note that this brace-placement also minimizes the number of empty
 +(or almost empty) lines, without any loss of readability. Thus, as the
 +supply of new-lines on your screen is not a renewable resource, you have
 +more empty lines to put comments on.
 +
 +Do not unnecessarily use braces where a single statement will do.
 +
 + if (condition)
 + action();
 +
 +and
 +
 + if (condition)
 + do_this();​
 + else
 + do_that();​
 +
 +This does not apply if one branch of a conditional statement is not a 
 +single statement. Use braces in both branches.
 +
 + if (condition) {
 + do_this();​
 + do_that();​
 + } else {
 + otherwise();​
 + }
 +
 +
 +=== Spaces ===
 +
 +Use of spaces depends (mostly) on function-versus-keyword usage. Use a space
 +after (most) keywords. The notable exceptions are sizeof, typeof, alignof, ​
 +and __attribute__,​ which look somewhat like functions (and are usually used
 +with parentheses in Linux, although they are not required in the language, ​
 +as in: "​sizeof info" after "​struct fileinfo info;" is declared).
 +
 +So use a space after these keywords:
 +
 + if, switch, case, for, do, while
 +
 +but not with sizeof, typeof, alignof. E.g.:
 +
 + s = sizeof(struct file);
 +
 +Do not add spaces around (inside) parenthesized expressions.
 +This example is **bad**:
 +
 + s = sizeof( struct file );
 +
 +When declaring pointer data or a function that returns a pointer type, the
 +preferred use of '​*'​ is adjacent to the data name or function name and not
 +adjacent to the type name. Examples:
 +
 + char *banner;
 + unsigned long long memparse(char *ptr, char **retptr);
 + char *match_strdup(substring_t *s);
 +
 +Use one space around (on each side of) most binary and ternary operators,
 +such as any of these:
 + =  +  -  <  >  *  /  %  |  &  ^  <=  >=  ==  !=  ?  :
 +
 +but no space after unary operators:
 + & ​ *  +  -  ~  !  sizeof ​ typeof ​ alignof ​ defined
 +
 +no space before the postfix increment & decrement unary operators:
 + ++  --
 +
 +no space after the prefix increment & decrement unary operators:
 + ++  --
 +
 +and no space around the '​.'​ and "​->"​ structure member operators.
 +
 +Do not leave trailing whitespace at the ends of lines. Some editors with
 +"​smart"​ indentation will insert whitespace at the beginning of new lines as
 +appropriate,​ so you can start typing the next line of code right away.
 +However, some such editors do not remove the whitespace if you end up not
 +putting a line of code there, such as if you leave a blank line. As a result,
 +you end up with lines containing trailing whitespace.
 +
 +
 +
 +
 +
 +
 +
 +
 +
 +--------------------------------------------------------------------------+-----
 +
 +
 +
 +
 +
  
  
Zeile 13: Zeile 424:
  
  
 +====== Version 4 ======
 +original linux kernel
 +################################################################################​
  
  

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