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Annotation of cci/usr/src/man/man3/varargs.3, revision 1.1

1.1     ! root        1: .TH VARARGS 3  "19 January 1983"
        !             2: .SH NAME
        !             3: varargs \- variable argument list
        !             4: .SH SYNOPSIS
        !             5: .B "#include <varargs.h>"
        !             6: .PP
        !             7: .I function\c
        !             8: .RB ( va_alist )
        !             9: .br
        !            10: .B va_dcl
        !            11: .br
        !            12: .B va_list
        !            13: .IR pvar ;
        !            14: .br
        !            15: .B va_start\c
        !            16: .RI ( pvar );
        !            17: .br
        !            18: f =
        !            19: .B va_arg\c
        !            20: .RI ( pvar ,
        !            21: .IR type );
        !            22: .br
        !            23: .B va_end\c
        !            24: .RI ( pvar );
        !            25: .SH DESCRIPTION
        !            26: This set of macros provides a means of writing portable procedures that
        !            27: accept variable argument lists.
        !            28: Routines having variable argument lists (such as
        !            29: .IR printf (3))
        !            30: that do not use varargs are inherently nonportable, since different
        !            31: machines use different argument passing conventions.
        !            32: .PP
        !            33: .B va_alist
        !            34: is used in a function header to declare a variable argument list.
        !            35: .PP
        !            36: .B va_dcl
        !            37: is a declaration for
        !            38: .BR va_alist .
        !            39: Note that there is no semicolon after
        !            40: .B va_dcl.
        !            41: .PP
        !            42: .B va_list
        !            43: is a type which can be used for the variable
        !            44: .IR pvar ,
        !            45: which is used to traverse the list.
        !            46: One such variable must always be declared.
        !            47: .PP
        !            48: .B va_start\c
        !            49: .RI (pvar)
        !            50: is called to initialize
        !            51: .I pvar
        !            52: to the beginning of the list.
        !            53: .PP
        !            54: .B va_arg\c
        !            55: .RI ( pvar ,
        !            56: .IR type )
        !            57: will return the next argument in the list pointed to by
        !            58: .IR pvar .
        !            59: .I Type
        !            60: is the type the argument is expected to be.
        !            61: Different types can be mixed, but it is up
        !            62: to the routine to know what type of argument is
        !            63: expected, since it cannot be determined at runtime.
        !            64: .PP
        !            65: .B va_end\c
        !            66: .RI ( pvar )
        !            67: is used to finish up.
        !            68: .PP
        !            69: Multiple traversals, each bracketed by
        !            70: .B va_start
        !            71: \&...
        !            72: .B va_end,
        !            73: are possible.
        !            74: .SH EXAMPLE
        !            75: .nf
        !            76:        \fB#include\fP <varargs.h>
        !            77:        execl(\fBva_alist\fP)
        !            78:        \fBva_dcl\fP
        !            79:        {
        !            80:                \fBva_list\fP ap;
        !            81:                \fBchar\fP *file;
        !            82:                \fBchar\fP *args[100];
        !            83:                \fBint\fP argno = 0;
        !            84: 
        !            85:                \fBva_start\fP(ap);
        !            86:                file = \fBva_arg(ap, \fBchar\fP *);
        !            87:                \fBwhile\fP (args[argno++] = \fBva_arg\fP(ap, \fBchar\fP *))
        !            88:                        \fB;\fP
        !            89:                \fBva_end\fP(ap);
        !            90:                \fBreturn\fP execv(file, args);
        !            91:        }
        !            92: .fi
        !            93: .SH BUGS
        !            94: It is up to the calling routine to determine how many arguments
        !            95: there are, since it is not possible to determine this from the
        !            96: stack frame.  For example,
        !            97: .I execl
        !            98: passes a 0 to signal the end of the list.
        !            99: .I Printf
        !           100: can tell how many arguments are supposed to be there by the format.

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