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       int ares_library_init_mem(int flags,
14                                 void *(*amalloc)(size_t),
15                                 void (*afree)(void *ptr),
16                                 void (*arealloc)(void *ptr, size_t size))
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DESCRIPTION

19       The  ares_library_init  function  performs  initializations  internally
20       required by the c-ares library that must take place  before  any  other
21       function provided by c-ares can be used in a program.
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23       This  function  must  be called at least once within the life of a pro‐
24       gram, before the program actually executes  any  other  c-ares  library
25       function.  Initializations done by this function remain effective until
26       a number of calls to ares_library_cleanup(3) equal  to  the  number  of
27       calls to this function are performed.
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29       Successive  calls  to  this function do nothing further, only the first
30       call done when c-ares is in an uninitialized state is  actually  effec‐
31       tive.
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33       The  flags  parameter  is a bit pattern that tells c-ares exactly which
34       features should be initialized, as described  below.  Set  the  desired
35       bits by ORing the values together. In normal operation you should spec‐
36       ify ARES_LIB_INIT_ALL. Don't use any other value unless you are  famil‐
37       iar with it and trying to control some internal c-ares feature.
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39       The  ares_library_init_mem function allows the caller to provide memory
40       management functions that the c-ares library will  be  use  instead  of
41       malloc(3), free(3) and realloc(3).
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43       This function is not thread safe.  You have to call it once the program
44       has started, but this call must be done before the program  starts  any
45       other  thread.  This  is required to avoid potential race conditions in
46       library   initialization,   and   also   due   to   the    fact    that
47       ares_library_init(3) might call functions from other libraries that are
48       thread unsafe, and could conflict with any other thread that is already
49       using these other libraries.
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51       Win32/64  application DLLs shall not call ares_library_init(3) from the
52       DllMain function. Doing so will produce deadlocks and other problems.
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FLAGS

55       ARES_LIB_INIT_ALL
56            Initialize everything possible. This sets all known bits.
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58       ARES_LIB_INIT_WIN32
59            Initialize Win32/64 specific libraries.
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61       ARES_LIB_INIT_NONE
62            Initialize nothing extra. This sets no bit.
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RETURN VALUE

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

71       This  function  was first introduced in c-ares version 1.7.0 along with
72       the definition of preprocessor symbol  CARES_HAVE_ARES_LIBRARY_INIT  as
73       an  indication  of  the  availability  of  this function. Its recursive
74       behavior,   which   requires   a   matching   number   of   calls    to
75       ares_library_cleanup() in order to deinitialize the library, is present
76       since c-ares version 1.10.0. Earlier versions  would  deinitialize  the
77       library on the first call to ares_library_cleanup().
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79       Since  the  introduction of this function it is absolutely mandatory to
80       call it for any Win32/64 program using c-ares.
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82       Non-Win32/64 systems can still use c-ares version 1.7.0 without calling
83       ares_library_init(3)  due to the fact that currently it is nearly a do-
84       nothing function on non-Win32/64 platforms at this point.
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SEE ALSO

87       ares_library_cleanup(3), ares_strerror(3)
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AUTHOR

90       Yang Tse
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92       Copyright 1998 by the Massachusetts Institute of Technology.
93       Copyright (C) 2004-2009 by Daniel Stenberg.
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97                                  19 May 2009             ARES_LIBRARY_INIT(3)
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