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.\+/'
94 =========================
95 FAQ & Statement Reference
96 =========================
101 Comments should always use the standard C syntax. C++
102 style comments are not currently allowed.
104 The lines before a comment should be empty. If the comment directly
105 belongs to the following code, there should be no empty line
106 after the comment, except if the comment contains a summary
107 of multiple following code blocks.
115 * This is a multi line comment,
116 * which explains the logical steps we have to do:
118 * 1. We need to set i=5, because...
119 * 2. We need to call complex_fn1
122 /* This is a one line comment about i = 5. */
126 * This is a multi line comment,
127 * explaining the call to complex_fn1()
134 * @brief This is a doxygen comment.
136 * This is a more detailed explanation of
137 * this simple function.
139 * @param[in] param1 The parameter value of the function.
141 * @param[out] result1 The result value of the function.
143 * @return 0 on success and -1 on error.
145 int example(int param1, int *result1);
152 * This is a multi line comment,
153 * which explains the logical steps we have to do:
155 * 1. We need to set i=5, because...
156 * 2. We need to call complex_fn1
158 /* This is a one line comment about i = 5. */
161 * This is a multi line comment,
162 * explaining the call to complex_fn1()
168 /*This is a one line comment.*/
170 /* This is a multi line comment,
171 with some more words...*/
174 * This is a multi line comment,
175 * with some more words...*/
177 Indention & Whitespace & 80 columns
178 -----------------------------------
180 To avoid confusion, indentations have to be tabs with length 8 (not 8
181 ' ' characters). When wrapping parameters for function calls,
182 align the parameter list with the first parameter on the previous line.
183 Use tabs to get as close as possible and then fill in the final 7
184 characters or less with whitespace. For example,
186 var1 = foo(arg1, arg2,
189 The previous example is intended to illustrate alignment of function
190 parameters across lines and not as encourage for gratuitous line
191 splitting. Never split a line before columns 70 - 79 unless you
192 have a really good reason. Be smart about formatting.
194 One exception to the previous rule is function declarations and
195 definitions. In function declarations and definitions, either the
196 declaration is a one-liner, or each parameter is listed on its own
197 line. The rationale is that if there are many parameters, each one
198 should be on its own line to make tracking interface changes easier.
201 If, switch, & Code blocks
202 -------------------------
204 Always follow an 'if' keyword with a space but don't include additional
205 spaces following or preceding the parentheses in the conditional.
214 Yes we have a lot of code that uses the second form and we are trying
215 to clean it up without being overly intrusive.
217 Note that this is a rule about parentheses following keywords and not
218 functions. Don't insert a space between the name and left parentheses when
221 Braces for code blocks used by for, if, switch, while, do..while, etc.
222 should begin on the same line as the statement keyword and end on a line
223 of their own. You should always include braces, even if the block only
224 contains one statement. NOTE: Functions are different and the beginning left
225 brace should be located in the first column on the next line.
227 If the beginning statement has to be broken across lines due to length,
228 the beginning brace should be on a line of its own.
230 The exception to the ending rule is when the closing brace is followed by
231 another language keyword such as else or the closing while in a do..while
240 for (x=1; x<10; x++) {
244 for (really_really_really_really_long_var_name=0;
245 really_really_really_really_long_var_name<10;
246 really_really_really_really_long_var_name++)
248 print("%d\n", really_really_really_really_long_var_name);
252 printf("also good\n");
259 print("I'm in a loop!\n"); }
269 print("I should be in braces.\n");
275 While many people have been academically taught that "goto"s are
276 fundamentally evil, they can greatly enhance readability and reduce memory
277 leaks when used as the single exit point from a function. But in no Samba
278 world what so ever is a goto outside of a function or block of code a good
283 int function foo(int y)
289 z = malloc(sizeof(int) * y);
296 print("Allocated %d elements.\n", y);
310 Samba has large amounts of historical code which makes use of data types
311 commonly supported by the C99 standard. However, at the time such types
312 as boolean and exact width integers did not exist and Samba developers
313 were forced to provide their own. Now that these types are guaranteed to
314 be available either as part of the compiler C99 support or from
315 lib/replace/, new code should adhere to the following conventions:
317 * Booleans are of type "bool" (not BOOL)
318 * Boolean values are "true" and "false" (not True or False)
319 * Exact width integers are of type [u]int[8|16|32|64]_t
321 Most of the time a good name for a boolean variable is 'ok'. Here is an
322 example we often use:
331 It makes the code more readable and is easy to debug.
336 Samba tries to avoid "typedef struct { .. } x_t;" so we do always try to use
337 "struct x { .. };". We know there are still such typedefs in the code,
338 but for new code, please don't do that anymore.
343 All pointer variables MUST be initialized to NULL. History has
344 demonstrated that uninitialized pointer variables have lead to various
345 bugs and security issues.
347 Pointers MUST be initialized even if the assignment directly follows
348 the declaration, like pointer2 in the example below, because the
349 instructions sequence may change over time.
353 char *pointer1 = NULL;
354 char *pointer2 = NULL;
356 pointer2 = some_func2();
360 pointer1 = some_func1();
367 pointer2 = some_func2();
371 pointer1 = some_func1();
373 Make use of helper variables
374 ----------------------------
376 Please try to avoid passing function calls as function parameters
377 in new code. This makes the code much easier to read and
378 it's also easier to use the "step" command within gdb.
385 name = get_some_name();
390 ret = some_function_my_name(name);
396 ret = some_function_my_name(get_some_name());
399 Please try to avoid passing function return values to if- or
400 while-conditions. The reason for this is better handling of code under a
405 x = malloc(sizeof(short)*10);
407 fprintf(stderr, "Unable to alloc memory!\n");
412 if ((x = malloc(sizeof(short)*10)) == NULL ) {
413 fprintf(stderr, "Unable to alloc memory!\n");
416 There are exceptions to this rule. One example is walking a data structure in
419 while ((opt = poptGetNextOpt(pc)) != -1) {
420 ... do something with opt ...
423 But in general, please try to avoid this pattern.
426 Control-Flow changing macros
427 ----------------------------
429 Macros like NT_STATUS_NOT_OK_RETURN that change control flow
430 (return/goto/etc) from within the macro are considered bad, because
431 they look like function calls that never change control flow. Please
432 do not use them in new code.
434 The only exception is the test code that depends repeated use of calls
435 like CHECK_STATUS, CHECK_VAL and others.
441 Use these following macros instead of DEBUG:
443 DBG_ERR log level 0 error conditions
444 DBG_WARNING log level 1 warning conditions
445 DBG_NOTICE log level 3 normal, but significant, condition
446 DBG_INFO log level 5 informational message
447 DBG_DEBUG log level 10 debug-level message
451 DBG_ERR("Memory allocation failed\n");
452 DBG_DEBUG("Received %d bytes\n", count);
454 The messages from these macros are automatically prefixed with the