2009-05-19 23:00:28 +04:00
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.\" $Id$
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.\"
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.\" Copyright 1998 by the Massachusetts Institute of Technology.
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.\" Copyright (C) 2004-2009 by Daniel Stenberg
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.\"
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.\" Permission to use, copy, modify, and distribute this
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.\" software and its documentation for any purpose and without
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.\" fee is hereby granted, provided that the above copyright
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.\" notice appear in all copies and that both that copyright
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.\" notice and this permission notice appear in supporting
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.\" documentation, and that the name of M.I.T. not be used in
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.\" advertising or publicity pertaining to distribution of the
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.\" software without specific, written prior permission.
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.\" M.I.T. makes no representations about the suitability of
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.\" this software for any purpose. It is provided "as is"
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.\" without express or implied warranty.
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.\"
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.TH ARES_LIBRARY_INIT 3 "19 May 2009"
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.SH NAME
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ares_library_init \- c-ares library initialization
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.SH SYNOPSIS
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.nf
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.B #include <ares.h>
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.PP
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.B int ares_library_init(int \fIflags\fP)
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.PP
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.B cc file.c -lcares
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.fi
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.SH DESCRIPTION
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.PP
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The
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.B ares_library_init
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function performs initializations internally required by the c-ares
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library that must take place before any other function provided by
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c-ares can be used in a program.
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.PP
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This function must be called one time within the life of a program,
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before the program actually executes any other c-ares library function.
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Initializations done by this function remain effective until a
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call to \fIares_library_cleanup(3)\fP is performed.
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.PP
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Successive calls to this function do nothing, only the first call done
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when c-ares is in an uninitialized state is actually effective.
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.PP
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The
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.I flags
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parameter is a bit pattern that tells c-ares exactly which features
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should be initialized, as described below. Set the desired bits by
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ORing the values together. In normal operation you should specify
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\fIARES_LIB_INIT_ALL\fP. Don't use any other value unless you are
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familiar with it and trying to control some internal c-ares feature.
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.PP
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.B This function is not thread safe.
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You have to call it once the program has started, but this call must be done
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before the program starts any other thread. This is required to avoid
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potential race conditions in library initialization, and also due to the fact
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that \fIares_library_init(3)\fP might call functions from other libraries that
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are thread unsafe, and could conflict with any other thread that is already
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using these other libraries.
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.PP
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Win32/64 application DLLs shall not call \fIares_library_init(3)\fP from the
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DllMain function. Doing so will produce deadlocks and other problems.
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.SH FLAGS
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.TP 5
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.B ARES_LIB_INIT_ALL
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Initialize everything possible. This sets all known bits.
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.TP
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.B ARES_LIB_INIT_WIN32
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Initialize Win32/64 specific libraries.
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.TP
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.B ARES_LIB_INIT_NONE
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Initialize nothing extra. This sets no bit.
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.SH RETURN VALUE
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Upon successful completion, ares_library_init() will return 0. Otherwise, a
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non-zero error number will be returned to indicate the error. Except for
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\fIares_strerror(3)\fP, you shall not call any other c-ares function upon
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\fIares_library_init(3)\fP failure.
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.SH AVAILABILITY
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This function was first introduced in c-ares version 1.7.0 along with the
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definition of preprocessor symbol \fICARES_HAVE_ARES_LIBRARY_INIT\fP as an
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indication of the availability of this function.
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.PP
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Since the introduction of this function it is absolutely mandatory to
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call it for any Win32/64 program using c-ares.
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.PP
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Non-Win32/64 systems can still use c-ares version 1.7.0 without calling
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\fIares_library_init(3)\fP due to the fact that \fIcurrently\fP it is nearly
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a do-nothing function on non-Win32/64 platforms at this point.
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.SH SEE ALSO
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.BR ares_library_cleanup(3),
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.BR ares_strerror(3)
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.SH AUTHOR
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Yang Tse
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2009-05-20 06:12:23 +04:00
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.PP
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Copyright 1998 by the Massachusetts Institute of Technology.
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.br
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Copyright (C) 2004-2009 by Daniel Stenberg.
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