451 lines
13 KiB
Plaintext
451 lines
13 KiB
Plaintext
\input texinfo.tex
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@setfilename libc.info
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@ifinfo
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@format
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@dircategory Newlib
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@direntry
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* libc: (libc). The ANSI C library.
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@end direntry
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@end format
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@end ifinfo
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@ifinfo
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This file documents the ANSI C library.
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Copyright (C) 1992, 1993, 1994-2014 Red Hat, Inc.
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@file{libc} includes software developed by the
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University of California, Berkeley and its contributors.
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libc includes software developed by Martin Jackson, Graham Haley
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and Steve Chamberlain of Tadpole Technology and released to Cygnus.
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libc uses floating-point conversion software developed at AT&T, which
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includes this copyright information:
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The author of this software is David M. Gay.
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Copyright (c) 1991 by AT&T.
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Permission to use, copy, modify, and distribute this software for any
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purpose without fee is hereby granted, provided that this entire notice
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is included in all copies of any software which is or includes a copy
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or modification of this software and in all copies of the supporting
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documentation for such software.
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THIS SOFTWARE IS BEING PROVIDED "AS IS", WITHOUT ANY EXPRESS OR IMPLIED
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WARRANTY. IN PARTICULAR, NEITHER THE AUTHOR NOR AT&T MAKES ANY
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REPRESENTATION OR WARRANTY OF ANY KIND CONCERNING THE MERCHANTABILITY
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OF THIS SOFTWARE OR ITS FITNESS FOR ANY PARTICULAR PURPOSE.
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Permission is granted to make and distribute verbatim copies of
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this manual provided the copyright notice and this permission notice
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are preserved on all copies.
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@ignore
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Permission is granted to process this file through Tex and print the
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results, provided the printed document carries copying permission
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notice identical to this one except for the removal of this paragraph
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(this paragraph not being relevant to the printed manual).
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@end ignore
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Permission is granted to copy and distribute modified versions of this
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manual under the conditions for verbatim copying, subject to the terms
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of the GNU General Public License, which includes the provision that the
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entire resulting derived work is distributed under the terms of a
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permission notice identical to this one.
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Permission is granted to copy and distribute translations of this manual
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into another language, under the above conditions for modified versions.
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@end ifinfo
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@iftex
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@c @smallbook
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@c @cropmarks
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@finalout
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@setchapternewpage odd
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@settitle Red Hat newlib C Library, Full
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@titlepage
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@title The Red Hat newlib C Library
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@subtitle Full Configuration
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@sp 1
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@subtitle @code{libc} 2.5.0
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@subtitle December 2016
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@author {Steve Chamberlain}
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@author {Roland Pesch}
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@author {Red Hat Support}
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@author {Jeff Johnston}
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@page
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@tex
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{\parskip=0pt
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sac@@cygnus.com, pesch@@cygnus.com, jjohnstn@@redhat.com\hfill {\it The Red Hat newlib C Library}\par
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Copyright \copyright{} 1992, 1993, 1994-2004 Red Hat Inc.
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}
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\global\parindent=0pt % Steve likes it this way
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@end tex
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@file{libc} includes software developed by the
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University of California, Berkeley and its contributors.
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@file{libc} includes software developed by Martin Jackson, Graham Haley
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and Steve Chamberlain of Tadpole Technology and released to Cygnus.
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@file{libc} uses floating-point conversion software developed at AT&T,
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which includes this copyright information:
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@cartouche
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@quotation
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The author of this software is David M. Gay.
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Copyright (c) 1991 by AT&T.
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Permission to use, copy, modify, and distribute this software for any
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purpose without fee is hereby granted, provided that this entire notice
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is included in all copies of any software which is or includes a copy
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or modification of this software and in all copies of the supporting
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documentation for such software.
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THIS SOFTWARE IS BEING PROVIDED "AS IS", WITHOUT ANY EXPRESS OR IMPLIED
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WARRANTY. IN PARTICULAR, NEITHER THE AUTHOR NOR AT&T MAKES ANY
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REPRESENTATION OR WARRANTY OF ANY KIND CONCERNING THE MERCHANTABILITY
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OF THIS SOFTWARE OR ITS FITNESS FOR ANY PARTICULAR PURPOSE.
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@end quotation
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@end cartouche
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Permission is granted to make and distribute verbatim copies of
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this manual provided the copyright notice and this permission notice
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are preserved on all copies.
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Permission is granted to copy and distribute modified versions of this
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manual under the conditions for verbatim copying, subject to the terms
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of the GNU General Public License, which includes the provision that the
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entire resulting derived work is distributed under the terms of a
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permission notice identical to this one.
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Permission is granted to copy and distribute translations of this manual
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into another language, under the above conditions for modified versions.
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@end titlepage
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@end iftex
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@ifnottex
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@node Top
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@top The Red Hat newlib C Library
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@c The menu contents depend on the configuration, so we include them
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@c as a separate file
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@c switch to set SIGNALS on or off, according to whether config picks up
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@c signal subdirectory:
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@include sigset.texi
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@include extra.texi
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@include posix.texi
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@include stdio64.texi
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@include iconvset.texi
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@menu
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* Introduction::
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* Stdlib::
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* Ctype::
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* Stdio::
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@ifset STDIO64
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* Stdio64::
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@end ifset
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* Strings::
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* Wchar strings::
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@ifset SIGNALS
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* Signals::
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@end ifset
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* Timefns::
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* Locale::
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* Reentrancy::
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* Misc::
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@ifset POSIX
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* Posix::
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@end ifset
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* Syscalls::
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* Arglists::
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@ifset ICONV
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* Iconv::
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@end ifset
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* Overflow Protection::
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* Document Index::
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@end menu
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@end ifnottex
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@node Introduction
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@chapter Introduction
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This reference manual describes the functions provided by the Red Hat
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``newlib'' version of the standard ANSI C library. This document is not
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intended as an overview or a tutorial for the C library. Each library
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function is listed with a synopsis of its use, a brief description,
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return values (including error handling), and portability issues.
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Some of the library functions depend on support from the underlying
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operating system and may not be available on every platform. For
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embedded systems in particular, many of these underlying operating
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system services may not be available or may not be fully functional.
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The specific operating system subroutines required for a particular
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library function are listed in the ``Portability'' section of the
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function description. @xref{Syscalls}, for a description of the
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relevant operating system calls.
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@include targetdep.tex
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@node Arglists
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@chapter Variable Argument Lists
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The @code{printf} family of functions is defined to accept a variable
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number of arguments, rather than a fixed argument list. You can define
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your own functions with a variable argument list, by using macro
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definitions from either @file{stdarg.h} (for compatibility with ANSI C)
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or from @file{varargs.h} (for compatibility with a popular convention
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prior to ANSI C).
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@menu
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* Stdarg::
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* Varargs::
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@end menu
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@node Stdarg
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@section ANSI-standard macros, @file{stdarg.h}
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In ANSI C, a function has a variable number of arguments when its
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parameter list ends in an ellipsis (@code{...}). The parameter list
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must also include at least one explicitly named argument; that argument
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is used to initialize the variable list data structure.
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ANSI C defines three macros (@code{va_start}, @code{va_arg}, and
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@code{va_end}) to operate on variable argument lists. @file{stdarg.h}
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also defines a special type to represent variable argument lists: this
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type is called @code{va_list}.
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@menu
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* va_start::
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* va_arg::
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* va_end::
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@end menu
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@page
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@node va_start
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@subsection Initialize variable argument list
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@findex va_start
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@strong{Synopsis}
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@example
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#include <stdarg.h>
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void va_start(va_list @var{ap}, @var{rightmost});
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@end example
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@strong{Description}@*
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Use @code{va_start} to initialize the variable argument list @var{ap},
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so that @code{va_arg} can extract values from it. @var{rightmost} is
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the name of the last explicit argument in the parameter list (the
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argument immediately preceding the ellipsis @samp{...} that flags
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variable arguments in an ANSI C function header). You can only use
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@code{va_start} in a function declared using this ellipsis notation
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(not, for example, in one of its subfunctions).
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@strong{Returns}@*
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@code{va_start} does not return a result.
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@strong{Portability}@*
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ANSI C requires @code{va_start}.
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@page
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@node va_arg
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@subsection Extract a value from argument list
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@findex va_arg
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@strong{Synopsis}
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@example
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#include <stdarg.h>
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@var{type} va_arg(va_list @var{ap}, @var{type});
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@end example
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@strong{Description}@*
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@code{va_arg} returns the next unprocessed value from a variable
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argument list @var{ap} (which you must previously create with
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@var{va_start}). Specify the type for the value as the second parameter
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to the macro, @var{type}.
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You may pass a @code{va_list} object @var{ap} to a subfunction, and use
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@code{va_arg} from the subfunction rather than from the function
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actually declared with an ellipsis in the header; however, in that case
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you may @emph{only} use @code{va_arg} from the subfunction. ANSI C does
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not permit extracting successive values from a single variable-argument
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list from different levels of the calling stack.
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There is no mechanism for testing whether there is actually a next
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argument available; you might instead pass an argument count (or some
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other data that implies an argument count) as one of the fixed arguments
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in your function call.
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@strong{Returns}@*
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@code{va_arg} returns the next argument, an object of type @var{type}.
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@strong{Portability}@*
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ANSI C requires @code{va_arg}.
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@page
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@node va_end
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@subsection Abandon a variable argument list
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@findex va_end
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@strong{Synopsis}
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@example
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#include <stdarg.h>
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void va_end(va_list @var{ap});
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@end example
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@strong{Description}@*
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Use @code{va_end} to declare that your program will not use the variable
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argument list @var{ap} any further.
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@strong{Returns}@*
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@code{va_end} does not return a result.
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@strong{Portability}@*
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ANSI C requires @code{va_end}.
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@node Varargs
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@section Traditional macros, @file{varargs.h}
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If your C compiler predates ANSI C, you may still be able to use
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variable argument lists using the macros from the @file{varargs.h}
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header file. These macros resemble their ANSI counterparts, but have
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important differences in usage. In particular, since traditional C has
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no declaration mechanism for variable argument lists, two additional
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macros are provided simply for the purpose of defining functions with
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variable argument lists.
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As with @file{stdarg.h}, the type @code{va_list} is used to hold a data
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structure representing a variable argument list.
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@menu
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* va_alist::
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* va_start-trad::
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* va_arg-trad::
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* va_end-trad::
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@end menu
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@page
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@node va_alist
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@subsection Declare variable arguments
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@findex va_alist
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@findex va_dcl
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@strong{Synopsis}
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@example
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#include <varargs.h>
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@var{function}(va_alist)
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va_dcl
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@end example
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@strong{Description}@*
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To use the @file{varargs.h} version of variable argument lists, you must
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declare your function with a call to the macro @code{va_alist} as its
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argument list, and use @code{va_dcl} as the declaration. @emph{Do not
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use a semicolon after @code{va_dcl}.}
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@strong{Returns}@*
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These macros cannot be used in a context where a return is syntactically
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possible.
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@strong{Portability}@*
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@var{va_alist} and @var{va_dcl} were the most widespread method of
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declaring variable argument lists prior to ANSI C.
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@page
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@node va_start-trad
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@subsection Initialize variable argument list
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@findex va_start
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@strong{Synopsis}
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@example
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#include <varargs.h>
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va_list @var{ap};
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va_start(@var{ap});
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@end example
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@strong{Description}@*
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With the @file{varargs.h} macros, use @code{va_start} to initialize a
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data structure @var{ap} to permit manipulating a variable argument list.
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@var{ap} must have the type @var{va_alist}.
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@strong{Returns}@*
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@code{va_start} does not return a result.
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@strong{Portability}@*
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@code{va_start} is also defined as a macro in ANSI C, but the
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definitions are incompatible; the ANSI version has another parameter
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besides @var{ap}.
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@page
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@node va_arg-trad
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@subsection Extract a value from argument list
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@findex va_arg
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@strong{Synopsis}
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@example
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#include <varargs.h>
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@var{type} va_arg(va_list @var{ap}, @var{type});
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@end example
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@strong{Description}@*
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@code{va_arg} returns the next unprocessed value from a variable
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argument list @var{ap} (which you must previously create with
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@var{va_start}). Specify the type for the value as the second parameter
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to the macro, @var{type}.
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@strong{Returns}@*
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@code{va_arg} returns the next argument, an object of type @var{type}.
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@strong{Portability}@*
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The @code{va_arg} defined in @file{varargs.h} has the same syntax and
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usage as the ANSI C version from @file{stdarg.h}.
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@page
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@node va_end-trad
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@subsection Abandon a variable argument list
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@findex va_end
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@strong{Synopsis}
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@example
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#include <varargs.h>
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va_end(va_list @var{ap});
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@end example
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@strong{Description}@*
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Use @code{va_end} to declare that your program will not use the variable
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argument list @var{ap} any further.
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@strong{Returns}@*
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@code{va_end} does not return a result.
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@strong{Portability}@*
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The @code{va_end} defined in @file{varargs.h} has the same syntax and
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usage as the ANSI C version from @file{stdarg.h}.
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@node Document Index
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@unnumbered Document Index
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@printindex cp
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@tex
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% I think something like @@colophon should be in texinfo. In the
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% meantime:
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\long\def\colophon{\hbox to0pt{}\vfill
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\centerline{The body of this manual is set in}
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\centerline{\fontname\tenrm,}
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\centerline{with headings in {\bf\fontname\tenbf}}
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\centerline{and examples in {\tt\fontname\tentt}.}
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\centerline{{\it\fontname\tenit\/} and}
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\centerline{{\sl\fontname\tensl\/}}
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\centerline{are used for emphasis.}\vfill}
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\page\colophon
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% Blame: pesch@@cygnus.com, 28mar91.
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@end tex
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@contents
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@bye
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