ares_library_init(3)

1ARES_LIBRARY_INIT(3)       Library Functions Manual       ARES_LIBRARY_INIT(3)
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NAME

6       ares_library_init - c-ares library initialization
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SYNOPSIS

9       #include <ares.h>
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11       int ares_library_init(int flags)
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13       cc file.c -lcares
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DESCRIPTION

16       The  ares_library_init  function  performs  initializations  internally
17       required by the c-ares library that must take place  before  any  other
18       function provided by c-ares can be used in a program.
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20       This  function  must  be  called one time within the life of a program,
21       before the program actually executes any other c-ares library function.
22       Initializations  done by this function remain effective until a call to
23       ares_library_cleanup(3) is performed.
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25       Successive calls to this function do nothing, only the first call  done
26       when c-ares is in an uninitialized state is actually effective.
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28       The  flags  parameter  is a bit pattern that tells c-ares exactly which
29       features should be initialized, as described  below.  Set  the  desired
30       bits by ORing the values together. In normal operation you should spec‐
31       ify ARES_LIB_INIT_ALL. Don't use any other value unless you are  famil‐
32       iar with it and trying to control some internal c-ares feature.
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34       This function is not thread safe.  You have to call it once the program
35       has started, but this call must be done before the program  starts  any
36       other  thread.  This  is required to avoid potential race conditions in
37       library   initialization,   and   also   due   to   the    fact    that
38       ares_library_init(3) might call functions from other libraries that are
39       thread unsafe, and could conflict with any other thread that is already
40       using these other libraries.
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42       Win32/64  application DLLs shall not call ares_library_init(3) from the
43       DllMain function. Doing so will produce deadlocks and other problems.
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FLAGS

46       ARES_LIB_INIT_ALL
47            Initialize everything possible. This sets all known bits.
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49       ARES_LIB_INIT_WIN32
50            Initialize Win32/64 specific libraries.
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52       ARES_LIB_INIT_NONE
53            Initialize nothing extra. This sets no bit.
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RETURN VALUE

56       Upon successful completion, ares_library_init() will return 0.   Other‐
57       wise,  a  non-zero error number will be returned to indicate the error.
58       Except for ares_strerror(3), you shall not call any other c-ares  func‐
59       tion upon ares_library_init(3) failure.
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AVAILABILITY

62       This  function  was first introduced in c-ares version 1.7.0 along with
63       the definition of preprocessor symbol  CARES_HAVE_ARES_LIBRARY_INIT  as
64       an indication of the availability of this function.
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66       Since  the  introduction of this function it is absolutely mandatory to
67       call it for any Win32/64 program using c-ares.
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69       Non-Win32/64 systems can still use c-ares version 1.7.0 without calling
70       ares_library_init(3)  due to the fact that currently it is nearly a do-
71       nothing function on non-Win32/64 platforms at this point.
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AUTHOR

77       Yang Tse
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79       Copyright 1998 by the Massachusetts Institute of Technology.
80       Copyright (C) 2004-2009 by Daniel Stenberg.
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84                                  19 May 2009             ARES_LIBRARY_INIT(3)