- commented author name and email address(es)
- commented GPL boilerplate
- commented longer description / notes for the program (if needed)
- - #includes and #defines
+ - #includes of .h files with angle brackets (<>) around them
+ - #includes of .h files with quotes ("") around them
+ - #defines (if any, note the section below titled "Avoid the Preprocessor")
- const and global variables
- function declarations (if necessary)
- function implementations
Spacing around Parentheses
~~~~~~~~~~~~~~~~~~~~~~~~~~
-Put a space between C keywords and left parens, but not between
-function names and the left paren that starts it's parameter list (whether it
-is being declared or called). Examples:
+Put a space between C keywords and left parens, but not between function names
+and the left paren that starts it's parameter list (whether it is being
+declared or called). Examples:
Don't do this:
-
Variable and Function Names
---------------------------
Exceptions:
- - Enums, macros, and constant variables should all be in upper-case with
- words optionally seperatedy by underscores (i.e. FIFOTYPE, ISBLKDEV()).
+ - Enums, macros, and constant variables are occasionally written in all
+ upper-case with words optionally seperatedy by underscores (i.e. FIFOTYPE,
+ ISBLKDEV()).
- Nobody is going to get mad at you for using 'pvar' as the name of a
variable that is a pointer to 'var'.
-Note: The Busybox codebase is very much a mixture of code gathered from a
-variety of sources. This explains why the current codebase contains such a
-hodge-podge of different naming styles (Java, Pascal, K&R, just-plain-weird,
-etc.). The K&R guideline explained above should therefore be used on new files
-that are added to the repository. Furthermore, the maintainer of an existing
-file that uses alternate naming conventions should -- at his own convenience
--- convert those names over to K&R style; converting variable names is a very
-low priority task. Perhaps in the future we will include some magical Perl
-script that can go through and convert variable names, left as an exercise for
-the reader for now.
-For the time being, if you want to do a search-and-replace of a variable name
-in different files, do the following in the busybox directory:
+Converting to K&R
+~~~~~~~~~~~~~~~~~
+
+The Busybox codebase is very much a mixture of code gathered from a variety of
+sources. This explains why the current codebase contains such a hodge-podge of
+different naming styles (Java, Pascal, K&R, just-plain-weird, etc.). The K&R
+guideline explained above should therefore be used on new files that are added
+to the repository. Furthermore, the maintainer of an existing file that uses
+alternate naming conventions should, at his own convenience, convert those
+names over to K&R style. Converting variable names is a very low priority
+task.
+
+If you want to do a search-and-replace of a single variable name in different
+files, you can do the following in the busybox directory:
$ perl -pi -e 's/\bOldVar\b/new_var/g' *.[ch]
+If you want to convert all the non-K&R vars in your file all at once, follow
+these steps:
+
+ - In the busybox directory type 'examples/mk2knr.pl files-to-convert'. This
+ does not do the actual conversion, rather, it generates a script called
+ 'convertme.pl' that shows what will be converted, giving you a chance to
+ review the changes beforehand.
+
+ - Review the 'convertme.pl' script that gets generated in the busybox
+ directory and remove / edit any of the substitutions in there. Please
+ especially check for false positives (strings that should not be
+ converted).
+
+ - Type './convertme.pl same-files-as-before' to perform the actual
+ conversion.
+
+ - Compile and see if everything still works.
+
+Please be aware of changes that have cascading effects into other files. For
+example, if you're changing the name of something in, say utility.c, you
+should probably run 'examples/mk2knr.pl utility.c' at first, but when you run
+the 'convertme.pl' script you should run it on _all_ files like so:
+'./convertme.pl *.[ch]'.
+
Avoid The Preprocessor
}
Static inline functions are greatly preferred over macros. They provide type
-safety, have no length limitations, no formatting limitations, and under gcc
-they are as cheap as macros. Besides, really long macros with backslashes at
-the end of each line are ugly as sin.
+safety, have no length limitations, no formatting limitations, have an actual
+return value, and under gcc they are as cheap as macros. Besides, really long
+macros with backslashes at the end of each line are ugly as sin.
The Folly of #ifdef
~~~~~~~~~~~~~~~~~~~
Code cluttered with ifdefs is difficult to read and maintain. Don't do it.
-Instead, put your ifdefs in a header, and conditionally define 'static inline'
-functions, (or *maybe* macros), which are used in the code.
+Instead, put your ifdefs at the top of your .c file (or in a header), and
+conditionally define 'static inline' functions, (or *maybe* macros), which are
+used in the code.
Don't do this:
ret = my_func(bar, baz);
if (!ret)
return -1;
- #ifdef BB_FEATURE_FUNKY
+ #ifdef CONFIG_FEATURE_FUNKY
maybe_do_funky_stuff(bar, baz);
#endif
(in .h header file)
- #ifdef BB_FEATURE_FUNKY
+ #ifdef CONFIG_FEATURE_FUNKY
static inline void maybe_do_funky_stuff (int bar, int baz)
{
/* lotsa code in here */
A macro is declared in busybox.h that implements compile-time selection
between xmalloc() and stack creation, so you can code the line in question as
- RESERVE_BB_BUFFER(buffer, BUFSIZ);
+ RESERVE_CONFIG_BUFFER(buffer, BUFSIZ);
and the right thing will happen, based on your configuration.
formatting, options, etc.), model it after the equivalent GNU program.
Doesn't matter how that program behaves on some other flavor of *NIX; doesn't
matter what the POSIX standard says or doesn't say, just model Busybox
-programs after their GNU counterparts and nobody has to get hurt.
+programs after their GNU counterparts and it will make life easier on (nearly)
+everyone.
The only time we deviate from emulating the GNU behavior is when:
There is an optimal ammount of commenting that a program can have; you can
comment too much as well as too little.
-A picture is really worth a thousand words here, so here is an example that
-illustrates emphasizing logical blocks:
+A picture is really worth a thousand words here, the following example
+illustrates how to emphasize logical blocks:
while (line = get_line_from_file(fp)) {
/* eat the newline, if any */
- if (line[strlen(line)-1] == '\n') {
- line[strlen(line)-1] = '\0';
- }
+ chomp(line);
/* ignore blank lines */
if (strlen(file_to_act_on) == 0) {
}
-Testing Guidelines
-~~~~~~~~~~~~~~~~~~
+Processing Options with getopt
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+If your applet needs to process command-line switches, please use getopt() to
+do so. Numerous examples can be seen in many of the existing applets, but
+basically it boils down to two things: at the top of the .c file, have this
+line in the midst of your #includes:
+
+ #include <getopt.h>
+
+And a code block similar to the following near the top of your applet_main()
+routine:
-It's considered good form to test your new feature before you submit a patch
-to the mailing list, and especially before you commit a change to CVS. Here
-are some guidelines on testing your changes.
+ while ((opt = getopt(argc, argv, "abc")) > 0) {
+ switch (opt) {
+ case 'a':
+ do_a_opt = 1;
+ break;
+ case 'b':
+ do_b_opt = 1;
+ break;
+ case 'c':
+ do_c_opt = 1;
+ break;
+ default:
+ show_usage(); /* in utility.c */
+ }
+ }
- - Always test busybox applets against GNU counterparts and make sure the
- behavior / output is identical between the two.
+If your applet takes no options (such as 'init'), there should be a line
+somewhere in the file reads:
- - Try several different permutations and combinations of the features you're
- adding and make sure they all work. (Make sure one feature does not
- interfere with another, etc.)
+ /* no options, no getopt */
- - Make sure you test compiling against the source both with the feature
- turned on and turned off in Config.h and make sure busybox compiles cleanly
- both ways.
+That way, when people go grepping to see which applets need to be converted to
+use getopt, they won't get false positives.
+Additional Note: Do not use the getopt_long library function and do not try to
+hand-roll your own long option parsing. Busybox applets should only support
+short options. Explanations and examples of the short options should be
+documented in usage.h.
projects / oweals / busybox.git / blobdiff