1 Coding conventions in the Samba tree
2 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
10 Coding style guidelines are about reducing the number of unnecessary
11 reformatting patches and making things easier for developers to work
13 You don't have to like them or even agree with them, but once put in place
14 we all have to abide by them (or vote to change them). However, coding
15 style should never outweigh coding itself and so the guidelines
16 described here are hopefully easy enough to follow as they are very
17 common and supported by tools and editors.
19 The basic style for C code, also mentioned in prog_guide4.txt, is the Linux kernel
20 coding style (See Documentation/CodingStyle in the kernel source tree). This
21 closely matches what most Samba developers use already anyways, with a few
22 exceptions as mentioned below.
24 The coding style for Python code is documented in PEP8,
25 http://www.python.org/pep/pep8 (with spaces).
26 If you have ever worked on another free software Python project, you are
27 probably already familiar with it.
29 But to save you the trouble of reading the Linux kernel style guide, here
32 * Maximum Line Width is 80 Characters
33 The reason is not about people with low-res screens but rather sticking
34 to 80 columns prevents you from easily nesting more than one level of
35 if statements or other code blocks. Use source3/script/count_80_col.pl
36 to check your changes.
38 * Use 8 Space Tabs to Indent
39 No whitespace fillers.
41 * No Trailing Whitespace
42 Use source3/script/strip_trail_ws.pl to clean up your files before
45 * Follow the K&R guidelines. We won't go through all of them here. Do you
46 have a copy of "The C Programming Language" anyways right? You can also use
47 the format_indent.sh script found in source3/script/ if all else fails.
57 Add the follow to your $HOME/.emacs file:
59 (add-hook 'c-mode-hook
62 (c-toggle-auto-state)))
67 (Thanks to SATOH Fumiyasu <fumiyas@osstech.jp> for these hints):
69 For the basic vi editor included with all variants of \*nix, add the
70 following to $HOME/.exrc:
75 For Vim, the following settings in $HOME/.vimrc will also deal with
76 displaying trailing whitespace:
78 if has("syntax") && (&t_Co > 2 || has("gui_running"))
80 function! ActivateInvisibleCharIndicator()
81 syntax match TrailingSpace "[ \t]\+$" display containedin=ALL
82 highlight TrailingSpace ctermbg=Red
84 autocmd BufNewFile,BufRead * call ActivateInvisibleCharIndicator()
86 " Show tabs, trailing whitespace, and continued lines visually
87 set list listchars=tab:»·,trail:·,extends:…
89 " highlight overly long lines same as TODOs.
91 autocmd BufNewFile,BufRead *.c,*.h exec 'match Todo /\%>' . &textwidth . 'v.\+/'
98 BreakBeforeBraces: Linux
99 AllowShortIfStatementsOnASingleLine: false
100 IndentCaseLabels: false
101 BinPackParameters: false
104 =========================
105 FAQ & Statement Reference
106 =========================
111 Comments should always use the standard C syntax. C++
112 style comments are not currently allowed.
114 The lines before a comment should be empty. If the comment directly
115 belongs to the following code, there should be no empty line
116 after the comment, except if the comment contains a summary
117 of multiple following code blocks.
125 * This is a multi line comment,
126 * which explains the logical steps we have to do:
128 * 1. We need to set i=5, because...
129 * 2. We need to call complex_fn1
132 /* This is a one line comment about i = 5. */
136 * This is a multi line comment,
137 * explaining the call to complex_fn1()
144 * @brief This is a doxygen comment.
146 * This is a more detailed explanation of
147 * this simple function.
149 * @param[in] param1 The parameter value of the function.
151 * @param[out] result1 The result value of the function.
153 * @return 0 on success and -1 on error.
155 int example(int param1, int *result1);
162 * This is a multi line comment,
163 * which explains the logical steps we have to do:
165 * 1. We need to set i=5, because...
166 * 2. We need to call complex_fn1
168 /* This is a one line comment about i = 5. */
171 * This is a multi line comment,
172 * explaining the call to complex_fn1()
178 /*This is a one line comment.*/
180 /* This is a multi line comment,
181 with some more words...*/
184 * This is a multi line comment,
185 * with some more words...*/
187 Indention & Whitespace & 80 columns
188 -----------------------------------
190 To avoid confusion, indentations have to be tabs with length 8 (not 8
191 ' ' characters). When wrapping parameters for function calls,
192 align the parameter list with the first parameter on the previous line.
193 Use tabs to get as close as possible and then fill in the final 7
194 characters or less with whitespace. For example,
196 var1 = foo(arg1, arg2,
199 The previous example is intended to illustrate alignment of function
200 parameters across lines and not as encourage for gratuitous line
201 splitting. Never split a line before columns 70 - 79 unless you
202 have a really good reason. Be smart about formatting.
204 One exception to the previous rule is function declarations and
205 definitions. In function declarations and definitions, either the
206 declaration is a one-liner, or each parameter is listed on its own
207 line. The rationale is that if there are many parameters, each one
208 should be on its own line to make tracking interface changes easier.
211 If, switch, & Code blocks
212 -------------------------
214 Always follow an 'if' keyword with a space but don't include additional
215 spaces following or preceding the parentheses in the conditional.
224 Yes we have a lot of code that uses the second form and we are trying
225 to clean it up without being overly intrusive.
227 Note that this is a rule about parentheses following keywords and not
228 functions. Don't insert a space between the name and left parentheses when
231 Braces for code blocks used by for, if, switch, while, do..while, etc.
232 should begin on the same line as the statement keyword and end on a line
233 of their own. You should always include braces, even if the block only
234 contains one statement. NOTE: Functions are different and the beginning left
235 brace should be located in the first column on the next line.
237 If the beginning statement has to be broken across lines due to length,
238 the beginning brace should be on a line of its own.
240 The exception to the ending rule is when the closing brace is followed by
241 another language keyword such as else or the closing while in a do..while
250 for (x=1; x<10; x++) {
254 for (really_really_really_really_long_var_name=0;
255 really_really_really_really_long_var_name<10;
256 really_really_really_really_long_var_name++)
258 print("%d\n", really_really_really_really_long_var_name);
262 printf("also good\n");
269 print("I'm in a loop!\n"); }
279 print("I should be in braces.\n");
285 While many people have been academically taught that "goto"s are
286 fundamentally evil, they can greatly enhance readability and reduce memory
287 leaks when used as the single exit point from a function. But in no Samba
288 world what so ever is a goto outside of a function or block of code a good
293 int function foo(int y)
299 z = malloc(sizeof(int) * y);
306 print("Allocated %d elements.\n", y);
320 Samba has large amounts of historical code which makes use of data types
321 commonly supported by the C99 standard. However, at the time such types
322 as boolean and exact width integers did not exist and Samba developers
323 were forced to provide their own. Now that these types are guaranteed to
324 be available either as part of the compiler C99 support or from
325 lib/replace/, new code should adhere to the following conventions:
327 * Booleans are of type "bool" (not BOOL)
328 * Boolean values are "true" and "false" (not True or False)
329 * Exact width integers are of type [u]int[8|16|32|64]_t
331 Most of the time a good name for a boolean variable is 'ok'. Here is an
332 example we often use:
341 It makes the code more readable and is easy to debug.
346 Samba tries to avoid "typedef struct { .. } x_t;" so we do always try to use
347 "struct x { .. };". We know there are still such typedefs in the code,
348 but for new code, please don't do that anymore.
353 All pointer variables MUST be initialized to NULL. History has
354 demonstrated that uninitialized pointer variables have lead to various
355 bugs and security issues.
357 Pointers MUST be initialized even if the assignment directly follows
358 the declaration, like pointer2 in the example below, because the
359 instructions sequence may change over time.
363 char *pointer1 = NULL;
364 char *pointer2 = NULL;
366 pointer2 = some_func2();
370 pointer1 = some_func1();
377 pointer2 = some_func2();
381 pointer1 = some_func1();
383 Make use of helper variables
384 ----------------------------
386 Please try to avoid passing function calls as function parameters
387 in new code. This makes the code much easier to read and
388 it's also easier to use the "step" command within gdb.
395 name = get_some_name();
400 ret = some_function_my_name(name);
406 ret = some_function_my_name(get_some_name());
409 Please try to avoid passing function return values to if- or
410 while-conditions. The reason for this is better handling of code under a
415 x = malloc(sizeof(short)*10);
417 fprintf(stderr, "Unable to alloc memory!\n");
422 if ((x = malloc(sizeof(short)*10)) == NULL ) {
423 fprintf(stderr, "Unable to alloc memory!\n");
426 There are exceptions to this rule. One example is walking a data structure in
429 while ((opt = poptGetNextOpt(pc)) != -1) {
430 ... do something with opt ...
433 But in general, please try to avoid this pattern.
436 Control-Flow changing macros
437 ----------------------------
439 Macros like NT_STATUS_NOT_OK_RETURN that change control flow
440 (return/goto/etc) from within the macro are considered bad, because
441 they look like function calls that never change control flow. Please
442 do not use them in new code.
444 The only exception is the test code that depends repeated use of calls
445 like CHECK_STATUS, CHECK_VAL and others.
453 frame = talloc_stackframe();
455 if (ret == LDB_SUCCESS) {
456 if (result->count == 0) {
457 ret = LDB_ERR_NO_SUCH_OBJECT;
459 struct ldb_message *match =
460 get_best_match(dn, result);
463 return LDB_ERR_OPERATIONS_ERROR;
465 *msg = talloc_move(mem_ctx, &match);
474 frame = talloc_stackframe();
476 if (ret != LDB_SUCCESS) {
481 if (result->count == 0) {
483 return LDB_ERR_NO_SUCH_OBJECT;
486 match = get_best_match(dn, result);
489 return LDB_ERR_OPERATIONS_ERROR;
492 *msg = talloc_move(mem_ctx, &match);
500 Use these following macros instead of DEBUG:
502 DBG_ERR log level 0 error conditions
503 DBG_WARNING log level 1 warning conditions
504 DBG_NOTICE log level 3 normal, but significant, condition
505 DBG_INFO log level 5 informational message
506 DBG_DEBUG log level 10 debug-level message
510 DBG_ERR("Memory allocation failed\n");
511 DBG_DEBUG("Received %d bytes\n", count);
513 The messages from these macros are automatically prefixed with the