Drop main() prototype. Syncs with NetBSD-8

[minix.git] / share / misc / style

/* $NetBSD: style,v 1.51 2013/03/08 16:50:02 christos Exp $ */

/*
 * The revision control tag appears first, with a blank line after it.
 * Copyright text appears after the revision control tag.
 */

/*
 * The NetBSD source code style guide.
 * (Previously known as KNF - Kernel Normal Form).
 *
 *      from: @(#)style 1.12 (Berkeley) 3/18/94
 */
/*
 * An indent(1) profile approximating the style outlined in
 * this document lives in /usr/share/misc/indent.pro.  It is a
 * useful tool to assist in converting code to KNF, but indent(1)
 * output generated using this profile must not be considered to
 * be an authoritative reference.
 */

/*
 * Source code revision control identifiers appear after any copyright
 * text.  Use the appropriate macros from <sys/cdefs.h>.  Usually only one
 * source file per program contains a __COPYRIGHT() section.
 * Historic Berkeley code may also have an __SCCSID() section.
 * Only one instance of each of these macros can occur in each file.
 * Don't use newlines in the identifiers.
 */
#include <sys/cdefs.h>
__COPYRIGHT("@(#) Copyright (c) 2008\
 The NetBSD Foundation, inc. All rights reserved.");
__RCSID("$NetBSD: style,v 1.51 2013/03/08 16:50:02 christos Exp $");

/*
 * VERY important single-line comments look like this.
 */

/* Most single-line comments look like this. */

/*
 * Multi-line comments look like this.  Make them real sentences.  Fill
 * them so they look like real paragraphs.
 */

/*
 * Attempt to wrap lines longer than 80 characters appropriately.
 * Refer to the examples below for more information.
 */

/*
 * EXAMPLE HEADER FILE:
 *
 * A header file should protect itself against multiple inclusion.
 * E.g, <sys/socket.h> would contain something like:
 */
#ifndef _SYS_SOCKET_H_
#define _SYS_SOCKET_H_
/*
 * Contents of #include file go between the #ifndef and the #endif at the end.
 */
#endif /* !_SYS_SOCKET_H_ */
/*
 * END OF EXAMPLE HEADER FILE.
 */

/*
 * If a header file requires structures, defines, typedefs, etc. from
 * another header file it should include that header file and not depend
 * on the including file for that header including both.  If there are
 * exceptions to this for specific headers it should be clearly documented
 * in the headers and, if appropriate, the documentation.  Nothing in this
 * rule should suggest relaxation of the multiple inclusion rule and the
 * application programmer should be free to include both regardless.
 */

/*
 * Kernel include files come first.
 */
#include <sys/param.h>          /* <sys/param.h> first, */
#include <sys/types.h>          /*   <sys/types.h> next, */
#include <sys/ioctl.h>          /*   and then the rest, */
#include <sys/socket.h>         /*   sorted lexicographically.  */
#include <sys/stat.h>
#include <sys/wait.h>           /* Non-local includes in brackets.  */

/*
 * If it's a network program, put the network include files next.
 * Group the includes files by subdirectory.
 */
#include <net/if.h>
#include <net/if_dl.h>
#include <net/route.h>
#include <netinet/in.h>
#include <protocols/rwhod.h>

/*
 * Then there's a blank line, followed by the /usr include files.
 * The /usr include files should be sorted lexicographically!
 */
#include <assert.h>
#include <errno.h>
#include <inttypes.h>
#include <stdio.h>
#include <stdlib.h>

/*
 * Global pathnames are defined in /usr/include/paths.h.  Pathnames local
 * to the program go in pathnames.h in the local directory.
 */
#include <paths.h>

/* Then, there's a blank line, and the user include files. */
#include "pathnames.h"          /* Local includes in double quotes. */

/*
 * ANSI function declarations for private functions (i.e. functions not used
 * elsewhere) and the main() function go at the top of the source module.
 * Don't associate a name with the types.  I.e. use:
 *      void function(int);
 * Use your discretion on indenting between the return type and the name, and
 * how to wrap a prototype too long for a single line.  In the latter case,
 * lining up under the initial left parenthesis may be more readable.
 * In any case, consistency is important!
 */
static char *function(int, int, float, int);
static int dirinfo(const char *, struct stat *, struct dirent *,
                   struct statfs *, int *, char **[]);
static void usage(void) __dead; /* declare functions that don't return dead */

/*
 * Macros are capitalized, parenthesized, and should avoid side-effects.
 * Spacing before and after the macro name may be any whitespace, though
 * use of TABs should be consistent through a file.
 * If they are an inline expansion of a function, the function is defined
 * all in lowercase, the macro has the same name all in uppercase.
 * If the macro is an expression, wrap the expression in parenthesis.
 * If the macro is more than a single statement, use ``do { ... } while (0)'',
 * so that a trailing semicolon works.  Right-justify the backslashes; it
 * makes it easier to read. The CONSTCOND comment is to satisfy lint(1).
 */
#define MACRO(v, w, x, y)                                               \
do {                                                                    \
        v = (x) + (y);                                                  \
        w = (y) + 2;                                                    \
} while (/* CONSTCOND */ 0)

#define DOUBLE(x) ((x) * 2)

/* Enum types are capitalized.  No comma on the last element. */
enum enumtype {
        ONE,
        TWO
} et;

/*
 * When declaring variables in structures, declare them organized by use in
 * a manner to attempt to minimize memory wastage because of compiler alignment
 * issues, then by size, and then by alphabetical order. E.g, don't use
 * ``int a; char *b; int c; char *d''; use ``int a; int b; char *c; char *d''.
 * Each variable gets its own type and line, although an exception can be made
 * when declaring bitfields (to clarify that it's part of the one bitfield).
 * Note that the use of bitfields in general is discouraged.
 *
 * Major structures should be declared at the top of the file in which they
 * are used, or in separate header files, if they are used in multiple
 * source files.  Use of the structures should be by separate declarations
 * and should be "extern" if they are declared in a header file.
 *
 * It may be useful to use a meaningful prefix for each member name.
 * E.g, for ``struct softc'' the prefix could be ``sc_''.
 */
struct foo {
        struct foo *next;       /* List of active foo */
        struct mumble amumble;  /* Comment for mumble */
        int bar;
        unsigned int baz:1,     /* Bitfield; line up entries if desired */
                     fuz:5,
                     zap:2;
        uint8_t flag;
};
struct foo *foohead;            /* Head of global foo list */

/* Make the structure name match the typedef. */
typedef struct BAR {
        int level;
} BAR;

/* C99 uintN_t is preferred over u_intN_t. */
uint32_t zero;

/*
 * All major routines should have a comment briefly describing what
 * they do.  The comment before the "main" routine should describe
 * what the program does.
 */
int
main(int argc, char *argv[])
{
        long num;
        int ch;
        char *ep;

        /*
         * At the start of main(), call setprogname() to set the program
         * name.  This does nothing on NetBSD, but increases portability
         * to other systems.
         */
        setprogname(argv[0]);

        /*
         * For consistency, getopt should be used to parse options.
         * Options should be sorted in the getopt call and the switch
         * statement, unless parts of the switch cascade.  For the
         * sorting order, see the usage() example below.  Don't forget
         * to add option descriptions to the usage and the manpage.
         * Elements in a switch statement that cascade should have a
         * FALLTHROUGH comment.  Numerical arguments should be checked
         * for accuracy.  Code that cannot be reached should have a
         * NOTREACHED comment.
         */
        while ((ch = getopt(argc, argv, "abn:")) != -1) {
                switch (ch) {           /* Indent the switch. */
                case 'a':               /* Don't indent the case. */
                        aflag = 1;
                        /* FALLTHROUGH */
                case 'b':
                        bflag = 1;
                        break;
                case 'n':
                        errno = 0;
                        num = strtol(optarg, &ep, 10);
                        if (num <= 0 || *ep != '\0' || (errno == ERANGE &&
                            (num == LONG_MAX || num == LONG_MIN)) )
                                errx(1, "illegal number -- %s", optarg);
                        break;
                case '?':
                default:
                        usage();
                        /* NOTREACHED */
                }
        }
        argc -= optind;
        argv += optind;

        /*
         * Space after keywords (while, for, return, switch).  No braces are
         * required for control statements with only a single statement,
         * unless it's a long statement.
         *
         * Forever loops are done with for's, not while's.
         */
        for (p = buf; *p != '\0'; ++p)
                continue;               /* Explicit no-op */
        for (;;)
                stmt;

        /*
         * Braces are required for control statements with a single statement
         * that may expand to nothing.
         */
#ifdef DEBUG_FOO
#define DPRINTF(a) printf a
#else
#define DPRINTF(a)
#endif
        if (broken) {
                DPRINTF(("broken is %d\n", broken));
        }

        /*
         * Parts of a for loop may be left empty.  Don't put declarations
         * inside blocks unless the routine is unusually complicated.
         */
        for (; cnt < 15; cnt++) {
                stmt1;
                stmt2;
        }

        /* Second level indents are four spaces. */
        while (cnt < 20)
                z = a + really + long + statement + that + needs + two + lines +
                    gets + indented + four + spaces + on + the + second +
                    and + subsequent + lines;

        /*
         * Closing and opening braces go on the same line as the else.
         * Don't add braces that aren't necessary except in cases where
         * there are ambiguity or readability issues.
         */
        if (test) {
                /*
                 * I have a long comment here.
                 */
#ifdef zorro
                z = 1;
#else
                b = 3;
#endif
        } else if (bar) {
                stmt;
                stmt;
        } else
                stmt;

        /* No spaces after function names. */
        if ((result = function(a1, a2, a3, a4)) == NULL)
                exit(1);

        /*
         * Unary operators don't require spaces, binary operators do.
         * Don't excessively use parenthesis, but they should be used if
         * statement is really confusing without them, such as:
         * a = b->c[0] + ~d == (e || f) || g && h ? i : j >> 1;
         */
        a = ((b->c[0] + ~d == (e || f)) || (g && h)) ? i : (j >> 1);
        k = !(l & FLAGS);

        /*
         * Exits should be EXIT_SUCCESS on success, and EXIT_FAILURE on
         * failure.  Don't denote all the possible exit points, using the
         * integers 1 through 127.  Avoid obvious comments such as "Exit
         * 0 on success.". Since main is a function that returns an int,
         * prefer returning from it, than calling exit.
         */
        return EXIT_SUCCESS;
}

/*
 * The function type must be declared on a line by itself
 * preceding the function.
 */
static char *
function(int a1, int a2, float fl, int a4)
{
        /*
         * When declaring variables in functions declare them sorted by size,
         * then in alphabetical order; multiple ones per line are okay.
         * Function prototypes should go in the include file "extern.h".
         * If a line overflows reuse the type keyword.
         *
         * DO NOT initialize variables in the declarations.
         */
        extern u_char one;
        extern char two;
        struct foo three, *four;
        double five;
        int *six, seven;
        char *eight, *nine, ten, eleven, twelve, thirteen;
        char fourteen, fifteen, sixteen;

        /*
         * Casts and sizeof's are not followed by a space.  NULL is any
         * pointer type, and doesn't need to be cast, so use NULL instead
         * of (struct foo *)0 or (struct foo *)NULL.  Also, test pointers
         * against NULL.  I.e. use:
         *
         *      (p = f()) == NULL
         * not:
         *      !(p = f())
         *
         * The notable exception here is variadic functions. Since our
         * code is designed to compile and work on different environments
         * where we don't have control over the NULL definition (on NetBSD
         * it is defined as ((void *)0), but on other systems it can be
         * defined as (0) and both definitions are valid under ANSI C), it
         * it advised to cast NULL to a pointer on varyadic functions,
         * because on machines where sizeof(pointer) != sizeof(int) and in
         * the absence of a prototype in scope, passing an un-casted NULL,
         * will result in passing an int on the stack instead of a pointer.
         *
         * Don't use `!' for tests unless it's a boolean.
         * E.g. use "if (*p == '\0')", not "if (!*p)".
         *
         * Routines returning ``void *'' should not have their return
         * values cast to more specific pointer types.
         *
         * Prefer sizeof(*var) over sizeof(type) because if type changes,
         * the change needs to be done in one place.
         *
         * Use err/warn(3), don't roll your own!
         */
        if ((four = malloc(sizeof(*four))) == NULL)
                err(1, NULL);
        if ((six = (int *)overflow()) == NULL)
                errx(1, "Number overflowed.");

        /* No parentheses are needed around the return value. */
        return eight;
}

/*
 * Use ANSI function declarations.  ANSI function braces look like
 * old-style (K&R) function braces.
 * As per the wrapped prototypes, use your discretion on how to format
 * the subsequent lines.
 */
static int
dirinfo(const char *p, struct stat *sb, struct dirent *de, struct statfs *sf,
        int *rargc, char **rargv[])
{       /* Insert an empty line if the function has no local variables. */

        /*
         * In system libraries, catch obviously invalid function arguments
         * using _DIAGASSERT(3).
         */
        _DIAGASSERT(p != NULL);
        _DIAGASSERT(filedesc != -1);

        if (stat(p, sb) < 0)
                err(1, "Unable to stat %s", p);

        /*
         * To printf quantities that might be larger that "long", include
         * <inttypes.h>, cast quantities to intmax_t or uintmax_t and use
         * PRI?MAX constants.
         */
        (void)printf("The size of %s is %" PRIdMAX " (%#" PRIxMAX ")\n", p,
            (intmax_t)sb->st_size, (uintmax_t)sb->st_size);

        /*
         * To printf quantities of known bit-width, use the corresponding
         * defines (generally only done within NetBSD for quantities that
         * exceed 32-bits).
         */
        (void)printf("%s uses %" PRId64 " blocks and has flags %#" PRIx32 "\n",
            p, sb->st_blocks, sb->st_flags);

        /*
         * There are similar constants that should be used with the *scanf(3)
         * family of functions: SCN?MAX, SCN?64, etc.
         */
}

/*
 * Functions that support variable numbers of arguments should look like this.
 * (With the #include <stdarg.h> appearing at the top of the file with the
 * other include files.)
 */
#include <stdarg.h>

void
vaf(const char *fmt, ...)
{
        va_list ap;

        va_start(ap, fmt);
        STUFF;
        va_end(ap);
                                /* No return needed for void functions. */
}

static void
usage(void)
{

        /*
         * Use printf(3), not fputs/puts/putchar/whatever, it's faster and
         * usually cleaner, not to mention avoiding stupid bugs.
         * Use snprintf(3) or strlcpy(3)/strlcat(3) instead of sprintf(3);
         * again to avoid stupid bugs.
         *
         * Usage statements should look like the manual pages.
         * Options w/o operands come first, in alphabetical order
         * inside a single set of braces, upper case before lower case
         * (AaBbCc...).  Next are options with operands, in the same
         * order, each in braces.  Then required arguments in the
         * order they are specified, followed by optional arguments in
         * the order they are specified.  A bar (`|') separates
         * either/or options/arguments, and multiple options/arguments
         * which are specified together are placed in a single set of
         * braces.
         *
         * Use getprogname() instead of hardcoding the program name.
         *
         * "usage: f [-aDde] [-b b_arg] [-m m_arg] req1 req2 [opt1 [opt2]]\n"
         * "usage: f [-a | -b] [-c [-de] [-n number]]\n"
         */
        (void)fprintf(stderr, "usage: %s [-ab]\n", getprogname());
        exit(EXIT_FAILURE);
}