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1 | |
2 | Linux kernel coding style | |
3 | ||
4 | This is a short document describing the preferred coding style for the | |
5 | linux kernel. Coding style is very personal, and I won't _force_ my | |
6 | views on anybody, but this is what goes for anything that I have to be | |
7 | able to maintain, and I'd prefer it for most other things too. Please | |
8 | at least consider the points made here. | |
9 | ||
10 | First off, I'd suggest printing out a copy of the GNU coding standards, | |
11 | and NOT read it. Burn them, it's a great symbolic gesture. | |
12 | ||
13 | Anyway, here goes: | |
14 | ||
15 | ||
16 | Chapter 1: Indentation | |
17 | ||
18 | Tabs are 8 characters, and thus indentations are also 8 characters. | |
19 | There are heretic movements that try to make indentations 4 (or even 2!) | |
20 | characters deep, and that is akin to trying to define the value of PI to | |
21 | be 3. | |
22 | ||
23 | Rationale: The whole idea behind indentation is to clearly define where | |
24 | a block of control starts and ends. Especially when you've been looking | |
25 | at your screen for 20 straight hours, you'll find it a lot easier to see | |
26 | how the indentation works if you have large indentations. | |
27 | ||
28 | Now, some people will claim that having 8-character indentations makes | |
29 | the code move too far to the right, and makes it hard to read on a | |
30 | 80-character terminal screen. The answer to that is that if you need | |
31 | more than 3 levels of indentation, you're screwed anyway, and should fix | |
32 | your program. | |
33 | ||
34 | In short, 8-char indents make things easier to read, and have the added | |
35 | benefit of warning you when you're nesting your functions too deep. | |
36 | Heed that warning. | |
37 | ||
38 | Don't put multiple statements on a single line unless you have | |
39 | something to hide: | |
40 | ||
41 | if (condition) do_this; | |
42 | do_something_everytime; | |
43 | ||
44 | Outside of comments, documentation and except in Kconfig, spaces are never | |
45 | used for indentation, and the above example is deliberately broken. | |
46 | ||
47 | Get a decent editor and don't leave whitespace at the end of lines. | |
48 | ||
49 | ||
50 | Chapter 2: Breaking long lines and strings | |
51 | ||
52 | Coding style is all about readability and maintainability using commonly | |
53 | available tools. | |
54 | ||
55 | The limit on the length of lines is 80 columns and this is a hard limit. | |
56 | ||
57 | Statements longer than 80 columns will be broken into sensible chunks. | |
58 | Descendants are always substantially shorter than the parent and are placed | |
59 | substantially to the right. The same applies to function headers with a long | |
60 | argument list. Long strings are as well broken into shorter strings. | |
61 | ||
62 | void fun(int a, int b, int c) | |
63 | { | |
64 | if (condition) | |
65 | printk(KERN_WARNING "Warning this is a long printk with " | |
66 | "3 parameters a: %u b: %u " | |
67 | "c: %u \n", a, b, c); | |
68 | else | |
69 | next_statement; | |
70 | } | |
71 | ||
72 | Chapter 3: Placing Braces | |
73 | ||
74 | The other issue that always comes up in C styling is the placement of | |
75 | braces. Unlike the indent size, there are few technical reasons to | |
76 | choose one placement strategy over the other, but the preferred way, as | |
77 | shown to us by the prophets Kernighan and Ritchie, is to put the opening | |
78 | brace last on the line, and put the closing brace first, thusly: | |
79 | ||
80 | if (x is true) { | |
81 | we do y | |
82 | } | |
83 | ||
84 | However, there is one special case, namely functions: they have the | |
85 | opening brace at the beginning of the next line, thus: | |
86 | ||
87 | int function(int x) | |
88 | { | |
89 | body of function | |
90 | } | |
91 | ||
92 | Heretic people all over the world have claimed that this inconsistency | |
93 | is ... well ... inconsistent, but all right-thinking people know that | |
94 | (a) K&R are _right_ and (b) K&R are right. Besides, functions are | |
95 | special anyway (you can't nest them in C). | |
96 | ||
97 | Note that the closing brace is empty on a line of its own, _except_ in | |
98 | the cases where it is followed by a continuation of the same statement, | |
99 | ie a "while" in a do-statement or an "else" in an if-statement, like | |
100 | this: | |
101 | ||
102 | do { | |
103 | body of do-loop | |
104 | } while (condition); | |
105 | ||
106 | and | |
107 | ||
108 | if (x == y) { | |
109 | .. | |
110 | } else if (x > y) { | |
111 | ... | |
112 | } else { | |
113 | .... | |
114 | } | |
115 | ||
116 | Rationale: K&R. | |
117 | ||
118 | Also, note that this brace-placement also minimizes the number of empty | |
119 | (or almost empty) lines, without any loss of readability. Thus, as the | |
120 | supply of new-lines on your screen is not a renewable resource (think | |
121 | 25-line terminal screens here), you have more empty lines to put | |
122 | comments on. | |
123 | ||
124 | ||
125 | Chapter 4: Naming | |
126 | ||
127 | C is a Spartan language, and so should your naming be. Unlike Modula-2 | |
128 | and Pascal programmers, C programmers do not use cute names like | |
129 | ThisVariableIsATemporaryCounter. A C programmer would call that | |
130 | variable "tmp", which is much easier to write, and not the least more | |
131 | difficult to understand. | |
132 | ||
133 | HOWEVER, while mixed-case names are frowned upon, descriptive names for | |
134 | global variables are a must. To call a global function "foo" is a | |
135 | shooting offense. | |
136 | ||
137 | GLOBAL variables (to be used only if you _really_ need them) need to | |
138 | have descriptive names, as do global functions. If you have a function | |
139 | that counts the number of active users, you should call that | |
140 | "count_active_users()" or similar, you should _not_ call it "cntusr()". | |
141 | ||
142 | Encoding the type of a function into the name (so-called Hungarian | |
143 | notation) is brain damaged - the compiler knows the types anyway and can | |
144 | check those, and it only confuses the programmer. No wonder MicroSoft | |
145 | makes buggy programs. | |
146 | ||
147 | LOCAL variable names should be short, and to the point. If you have | |
148 | some random integer loop counter, it should probably be called "i". | |
149 | Calling it "loop_counter" is non-productive, if there is no chance of it | |
150 | being mis-understood. Similarly, "tmp" can be just about any type of | |
151 | variable that is used to hold a temporary value. | |
152 | ||
153 | If you are afraid to mix up your local variable names, you have another | |
154 | problem, which is called the function-growth-hormone-imbalance syndrome. | |
155 | See next chapter. | |
156 | ||
157 | ||
226a6b84 RD |
158 | Chapter 5: Typedefs |
159 | ||
160 | Please don't use things like "vps_t". | |
161 | ||
162 | It's a _mistake_ to use typedef for structures and pointers. When you see a | |
163 | ||
164 | vps_t a; | |
165 | ||
166 | in the source, what does it mean? | |
167 | ||
168 | In contrast, if it says | |
169 | ||
170 | struct virtual_container *a; | |
171 | ||
172 | you can actually tell what "a" is. | |
173 | ||
174 | Lots of people think that typedefs "help readability". Not so. They are | |
175 | useful only for: | |
176 | ||
177 | (a) totally opaque objects (where the typedef is actively used to _hide_ | |
178 | what the object is). | |
179 | ||
180 | Example: "pte_t" etc. opaque objects that you can only access using | |
181 | the proper accessor functions. | |
182 | ||
183 | NOTE! Opaqueness and "accessor functions" are not good in themselves. | |
184 | The reason we have them for things like pte_t etc. is that there | |
185 | really is absolutely _zero_ portably accessible information there. | |
186 | ||
187 | (b) Clear integer types, where the abstraction _helps_ avoid confusion | |
188 | whether it is "int" or "long". | |
189 | ||
190 | u8/u16/u32 are perfectly fine typedefs, although they fit into | |
191 | category (d) better than here. | |
192 | ||
193 | NOTE! Again - there needs to be a _reason_ for this. If something is | |
194 | "unsigned long", then there's no reason to do | |
195 | ||
196 | typedef unsigned long myflags_t; | |
197 | ||
198 | but if there is a clear reason for why it under certain circumstances | |
199 | might be an "unsigned int" and under other configurations might be | |
200 | "unsigned long", then by all means go ahead and use a typedef. | |
201 | ||
202 | (c) when you use sparse to literally create a _new_ type for | |
203 | type-checking. | |
204 | ||
205 | (d) New types which are identical to standard C99 types, in certain | |
206 | exceptional circumstances. | |
207 | ||
208 | Although it would only take a short amount of time for the eyes and | |
209 | brain to become accustomed to the standard types like 'uint32_t', | |
210 | some people object to their use anyway. | |
211 | ||
212 | Therefore, the Linux-specific 'u8/u16/u32/u64' types and their | |
213 | signed equivalents which are identical to standard types are | |
214 | permitted -- although they are not mandatory in new code of your | |
215 | own. | |
216 | ||
217 | When editing existing code which already uses one or the other set | |
218 | of types, you should conform to the existing choices in that code. | |
219 | ||
220 | (e) Types safe for use in userspace. | |
221 | ||
222 | In certain structures which are visible to userspace, we cannot | |
223 | require C99 types and cannot use the 'u32' form above. Thus, we | |
224 | use __u32 and similar types in all structures which are shared | |
225 | with userspace. | |
226 | ||
227 | Maybe there are other cases too, but the rule should basically be to NEVER | |
228 | EVER use a typedef unless you can clearly match one of those rules. | |
229 | ||
230 | In general, a pointer, or a struct that has elements that can reasonably | |
231 | be directly accessed should _never_ be a typedef. | |
232 | ||
233 | ||
234 | Chapter 6: Functions | |
1da177e4 LT |
235 | |
236 | Functions should be short and sweet, and do just one thing. They should | |
237 | fit on one or two screenfuls of text (the ISO/ANSI screen size is 80x24, | |
238 | as we all know), and do one thing and do that well. | |
239 | ||
240 | The maximum length of a function is inversely proportional to the | |
241 | complexity and indentation level of that function. So, if you have a | |
242 | conceptually simple function that is just one long (but simple) | |
243 | case-statement, where you have to do lots of small things for a lot of | |
244 | different cases, it's OK to have a longer function. | |
245 | ||
246 | However, if you have a complex function, and you suspect that a | |
247 | less-than-gifted first-year high-school student might not even | |
248 | understand what the function is all about, you should adhere to the | |
249 | maximum limits all the more closely. Use helper functions with | |
250 | descriptive names (you can ask the compiler to in-line them if you think | |
251 | it's performance-critical, and it will probably do a better job of it | |
252 | than you would have done). | |
253 | ||
254 | Another measure of the function is the number of local variables. They | |
255 | shouldn't exceed 5-10, or you're doing something wrong. Re-think the | |
256 | function, and split it into smaller pieces. A human brain can | |
257 | generally easily keep track of about 7 different things, anything more | |
258 | and it gets confused. You know you're brilliant, but maybe you'd like | |
259 | to understand what you did 2 weeks from now. | |
260 | ||
261 | ||
226a6b84 | 262 | Chapter 7: Centralized exiting of functions |
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263 | |
264 | Albeit deprecated by some people, the equivalent of the goto statement is | |
265 | used frequently by compilers in form of the unconditional jump instruction. | |
266 | ||
267 | The goto statement comes in handy when a function exits from multiple | |
268 | locations and some common work such as cleanup has to be done. | |
269 | ||
270 | The rationale is: | |
271 | ||
272 | - unconditional statements are easier to understand and follow | |
273 | - nesting is reduced | |
274 | - errors by not updating individual exit points when making | |
275 | modifications are prevented | |
276 | - saves the compiler work to optimize redundant code away ;) | |
277 | ||
dc3d28d0 | 278 | int fun(int a) |
1da177e4 LT |
279 | { |
280 | int result = 0; | |
281 | char *buffer = kmalloc(SIZE); | |
282 | ||
283 | if (buffer == NULL) | |
284 | return -ENOMEM; | |
285 | ||
286 | if (condition1) { | |
287 | while (loop1) { | |
288 | ... | |
289 | } | |
290 | result = 1; | |
291 | goto out; | |
292 | } | |
293 | ... | |
294 | out: | |
295 | kfree(buffer); | |
296 | return result; | |
297 | } | |
298 | ||
226a6b84 | 299 | Chapter 8: Commenting |
1da177e4 LT |
300 | |
301 | Comments are good, but there is also a danger of over-commenting. NEVER | |
302 | try to explain HOW your code works in a comment: it's much better to | |
303 | write the code so that the _working_ is obvious, and it's a waste of | |
304 | time to explain badly written code. | |
305 | ||
306 | Generally, you want your comments to tell WHAT your code does, not HOW. | |
307 | Also, try to avoid putting comments inside a function body: if the | |
308 | function is so complex that you need to separately comment parts of it, | |
309 | you should probably go back to chapter 5 for a while. You can make | |
310 | small comments to note or warn about something particularly clever (or | |
311 | ugly), but try to avoid excess. Instead, put the comments at the head | |
312 | of the function, telling people what it does, and possibly WHY it does | |
313 | it. | |
314 | ||
e776eba0 PE |
315 | When commenting the kernel API functions, please use the kerneldoc format. |
316 | See the files Documentation/kernel-doc-nano-HOWTO.txt and scripts/kernel-doc | |
317 | for details. | |
1da177e4 | 318 | |
226a6b84 | 319 | Chapter 9: You've made a mess of it |
1da177e4 LT |
320 | |
321 | That's OK, we all do. You've probably been told by your long-time Unix | |
322 | user helper that "GNU emacs" automatically formats the C sources for | |
323 | you, and you've noticed that yes, it does do that, but the defaults it | |
324 | uses are less than desirable (in fact, they are worse than random | |
325 | typing - an infinite number of monkeys typing into GNU emacs would never | |
326 | make a good program). | |
327 | ||
328 | So, you can either get rid of GNU emacs, or change it to use saner | |
329 | values. To do the latter, you can stick the following in your .emacs file: | |
330 | ||
331 | (defun linux-c-mode () | |
332 | "C mode with adjusted defaults for use with the Linux kernel." | |
333 | (interactive) | |
334 | (c-mode) | |
335 | (c-set-style "K&R") | |
336 | (setq tab-width 8) | |
337 | (setq indent-tabs-mode t) | |
338 | (setq c-basic-offset 8)) | |
339 | ||
340 | This will define the M-x linux-c-mode command. When hacking on a | |
341 | module, if you put the string -*- linux-c -*- somewhere on the first | |
342 | two lines, this mode will be automatically invoked. Also, you may want | |
343 | to add | |
344 | ||
345 | (setq auto-mode-alist (cons '("/usr/src/linux.*/.*\\.[ch]$" . linux-c-mode) | |
346 | auto-mode-alist)) | |
347 | ||
348 | to your .emacs file if you want to have linux-c-mode switched on | |
349 | automagically when you edit source files under /usr/src/linux. | |
350 | ||
351 | But even if you fail in getting emacs to do sane formatting, not | |
352 | everything is lost: use "indent". | |
353 | ||
354 | Now, again, GNU indent has the same brain-dead settings that GNU emacs | |
355 | has, which is why you need to give it a few command line options. | |
356 | However, that's not too bad, because even the makers of GNU indent | |
357 | recognize the authority of K&R (the GNU people aren't evil, they are | |
358 | just severely misguided in this matter), so you just give indent the | |
359 | options "-kr -i8" (stands for "K&R, 8 character indents"), or use | |
360 | "scripts/Lindent", which indents in the latest style. | |
361 | ||
362 | "indent" has a lot of options, and especially when it comes to comment | |
363 | re-formatting you may want to take a look at the man page. But | |
364 | remember: "indent" is not a fix for bad programming. | |
365 | ||
366 | ||
226a6b84 | 367 | Chapter 10: Configuration-files |
1da177e4 LT |
368 | |
369 | For configuration options (arch/xxx/Kconfig, and all the Kconfig files), | |
370 | somewhat different indentation is used. | |
371 | ||
372 | Help text is indented with 2 spaces. | |
373 | ||
374 | if CONFIG_EXPERIMENTAL | |
375 | tristate CONFIG_BOOM | |
376 | default n | |
377 | help | |
378 | Apply nitroglycerine inside the keyboard (DANGEROUS) | |
379 | bool CONFIG_CHEER | |
380 | depends on CONFIG_BOOM | |
381 | default y | |
382 | help | |
383 | Output nice messages when you explode | |
384 | endif | |
385 | ||
386 | Generally, CONFIG_EXPERIMENTAL should surround all options not considered | |
387 | stable. All options that are known to trash data (experimental write- | |
388 | support for file-systems, for instance) should be denoted (DANGEROUS), other | |
389 | experimental options should be denoted (EXPERIMENTAL). | |
390 | ||
391 | ||
226a6b84 | 392 | Chapter 11: Data structures |
1da177e4 LT |
393 | |
394 | Data structures that have visibility outside the single-threaded | |
395 | environment they are created and destroyed in should always have | |
396 | reference counts. In the kernel, garbage collection doesn't exist (and | |
397 | outside the kernel garbage collection is slow and inefficient), which | |
398 | means that you absolutely _have_ to reference count all your uses. | |
399 | ||
400 | Reference counting means that you can avoid locking, and allows multiple | |
401 | users to have access to the data structure in parallel - and not having | |
402 | to worry about the structure suddenly going away from under them just | |
403 | because they slept or did something else for a while. | |
404 | ||
405 | Note that locking is _not_ a replacement for reference counting. | |
406 | Locking is used to keep data structures coherent, while reference | |
407 | counting is a memory management technique. Usually both are needed, and | |
408 | they are not to be confused with each other. | |
409 | ||
410 | Many data structures can indeed have two levels of reference counting, | |
411 | when there are users of different "classes". The subclass count counts | |
412 | the number of subclass users, and decrements the global count just once | |
413 | when the subclass count goes to zero. | |
414 | ||
415 | Examples of this kind of "multi-level-reference-counting" can be found in | |
416 | memory management ("struct mm_struct": mm_users and mm_count), and in | |
417 | filesystem code ("struct super_block": s_count and s_active). | |
418 | ||
419 | Remember: if another thread can find your data structure, and you don't | |
420 | have a reference count on it, you almost certainly have a bug. | |
421 | ||
422 | ||
226a6b84 | 423 | Chapter 12: Macros, Enums and RTL |
1da177e4 LT |
424 | |
425 | Names of macros defining constants and labels in enums are capitalized. | |
426 | ||
427 | #define CONSTANT 0x12345 | |
428 | ||
429 | Enums are preferred when defining several related constants. | |
430 | ||
431 | CAPITALIZED macro names are appreciated but macros resembling functions | |
432 | may be named in lower case. | |
433 | ||
434 | Generally, inline functions are preferable to macros resembling functions. | |
435 | ||
436 | Macros with multiple statements should be enclosed in a do - while block: | |
437 | ||
438 | #define macrofun(a, b, c) \ | |
439 | do { \ | |
440 | if (a == 5) \ | |
441 | do_this(b, c); \ | |
442 | } while (0) | |
443 | ||
444 | Things to avoid when using macros: | |
445 | ||
446 | 1) macros that affect control flow: | |
447 | ||
448 | #define FOO(x) \ | |
449 | do { \ | |
450 | if (blah(x) < 0) \ | |
451 | return -EBUGGERED; \ | |
452 | } while(0) | |
453 | ||
454 | is a _very_ bad idea. It looks like a function call but exits the "calling" | |
455 | function; don't break the internal parsers of those who will read the code. | |
456 | ||
457 | 2) macros that depend on having a local variable with a magic name: | |
458 | ||
459 | #define FOO(val) bar(index, val) | |
460 | ||
461 | might look like a good thing, but it's confusing as hell when one reads the | |
462 | code and it's prone to breakage from seemingly innocent changes. | |
463 | ||
464 | 3) macros with arguments that are used as l-values: FOO(x) = y; will | |
465 | bite you if somebody e.g. turns FOO into an inline function. | |
466 | ||
467 | 4) forgetting about precedence: macros defining constants using expressions | |
468 | must enclose the expression in parentheses. Beware of similar issues with | |
469 | macros using parameters. | |
470 | ||
471 | #define CONSTANT 0x4000 | |
472 | #define CONSTEXP (CONSTANT | 3) | |
473 | ||
474 | The cpp manual deals with macros exhaustively. The gcc internals manual also | |
475 | covers RTL which is used frequently with assembly language in the kernel. | |
476 | ||
477 | ||
226a6b84 | 478 | Chapter 13: Printing kernel messages |
1da177e4 LT |
479 | |
480 | Kernel developers like to be seen as literate. Do mind the spelling | |
481 | of kernel messages to make a good impression. Do not use crippled | |
482 | words like "dont" and use "do not" or "don't" instead. | |
483 | ||
484 | Kernel messages do not have to be terminated with a period. | |
485 | ||
486 | Printing numbers in parentheses (%d) adds no value and should be avoided. | |
487 | ||
488 | ||
226a6b84 | 489 | Chapter 14: Allocating memory |
af4e5a21 PE |
490 | |
491 | The kernel provides the following general purpose memory allocators: | |
492 | kmalloc(), kzalloc(), kcalloc(), and vmalloc(). Please refer to the API | |
493 | documentation for further information about them. | |
494 | ||
495 | The preferred form for passing a size of a struct is the following: | |
496 | ||
497 | p = kmalloc(sizeof(*p), ...); | |
498 | ||
499 | The alternative form where struct name is spelled out hurts readability and | |
500 | introduces an opportunity for a bug when the pointer variable type is changed | |
501 | but the corresponding sizeof that is passed to a memory allocator is not. | |
502 | ||
503 | Casting the return value which is a void pointer is redundant. The conversion | |
504 | from void pointer to any other pointer type is guaranteed by the C programming | |
505 | language. | |
506 | ||
507 | ||
226a6b84 | 508 | Chapter 15: The inline disease |
a771f2b8 AV |
509 | |
510 | There appears to be a common misperception that gcc has a magic "make me | |
511 | faster" speedup option called "inline". While the use of inlines can be | |
512 | appropriate (for example as a means of replacing macros, see Chapter 11), it | |
513 | very often is not. Abundant use of the inline keyword leads to a much bigger | |
514 | kernel, which in turn slows the system as a whole down, due to a bigger | |
515 | icache footprint for the CPU and simply because there is less memory | |
516 | available for the pagecache. Just think about it; a pagecache miss causes a | |
517 | disk seek, which easily takes 5 miliseconds. There are a LOT of cpu cycles | |
518 | that can go into these 5 miliseconds. | |
519 | ||
520 | A reasonable rule of thumb is to not put inline at functions that have more | |
521 | than 3 lines of code in them. An exception to this rule are the cases where | |
522 | a parameter is known to be a compiletime constant, and as a result of this | |
523 | constantness you *know* the compiler will be able to optimize most of your | |
524 | function away at compile time. For a good example of this later case, see | |
525 | the kmalloc() inline function. | |
526 | ||
527 | Often people argue that adding inline to functions that are static and used | |
528 | only once is always a win since there is no space tradeoff. While this is | |
529 | technically correct, gcc is capable of inlining these automatically without | |
530 | help, and the maintenance issue of removing the inline when a second user | |
531 | appears outweighs the potential value of the hint that tells gcc to do | |
532 | something it would have done anyway. | |
533 | ||
534 | ||
c16a02d6 AS |
535 | Chapter 16: Function return values and names |
536 | ||
537 | Functions can return values of many different kinds, and one of the | |
538 | most common is a value indicating whether the function succeeded or | |
539 | failed. Such a value can be represented as an error-code integer | |
540 | (-Exxx = failure, 0 = success) or a "succeeded" boolean (0 = failure, | |
541 | non-zero = success). | |
542 | ||
543 | Mixing up these two sorts of representations is a fertile source of | |
544 | difficult-to-find bugs. If the C language included a strong distinction | |
545 | between integers and booleans then the compiler would find these mistakes | |
546 | for us... but it doesn't. To help prevent such bugs, always follow this | |
547 | convention: | |
548 | ||
549 | If the name of a function is an action or an imperative command, | |
550 | the function should return an error-code integer. If the name | |
551 | is a predicate, the function should return a "succeeded" boolean. | |
552 | ||
553 | For example, "add work" is a command, and the add_work() function returns 0 | |
554 | for success or -EBUSY for failure. In the same way, "PCI device present" is | |
555 | a predicate, and the pci_dev_present() function returns 1 if it succeeds in | |
556 | finding a matching device or 0 if it doesn't. | |
557 | ||
558 | All EXPORTed functions must respect this convention, and so should all | |
559 | public functions. Private (static) functions need not, but it is | |
560 | recommended that they do. | |
561 | ||
562 | Functions whose return value is the actual result of a computation, rather | |
563 | than an indication of whether the computation succeeded, are not subject to | |
564 | this rule. Generally they indicate failure by returning some out-of-range | |
565 | result. Typical examples would be functions that return pointers; they use | |
566 | NULL or the ERR_PTR mechanism to report failure. | |
567 | ||
568 | ||
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226a6b84 | 570 | Appendix I: References |
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571 | |
572 | The C Programming Language, Second Edition | |
573 | by Brian W. Kernighan and Dennis M. Ritchie. | |
574 | Prentice Hall, Inc., 1988. | |
575 | ISBN 0-13-110362-8 (paperback), 0-13-110370-9 (hardback). | |
576 | URL: http://cm.bell-labs.com/cm/cs/cbook/ | |
577 | ||
578 | The Practice of Programming | |
579 | by Brian W. Kernighan and Rob Pike. | |
580 | Addison-Wesley, Inc., 1999. | |
581 | ISBN 0-201-61586-X. | |
582 | URL: http://cm.bell-labs.com/cm/cs/tpop/ | |
583 | ||
584 | GNU manuals - where in compliance with K&R and this text - for cpp, gcc, | |
5b0ed2c6 | 585 | gcc internals and indent, all available from http://www.gnu.org/manual/ |
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586 | |
587 | WG14 is the international standardization working group for the programming | |
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588 | language C, URL: http://www.open-std.org/JTC1/SC22/WG14/ |
589 | ||
590 | Kernel CodingStyle, by greg@kroah.com at OLS 2002: | |
591 | http://www.kroah.com/linux/talks/ols_2002_kernel_codingstyle_talk/html/ | |
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592 | |
593 | -- | |
226a6b84 | 594 | Last updated on 30 April 2006. |