NAME

       ares_library_init - c-ares library initialization

SYNOPSIS

       #include <ares.h>

       int ares_library_init(int flags)

       int ares_library_init_mem(int flags,
                                 void *(*amalloc)(size_t),
                                 void (*afree)(void *ptr),
                                 void (*arealloc)(void *ptr, size_t size))

DESCRIPTION

       The  ares_library_init  function  performs initializations internally required by the c-ares library that
       must take place before any other function provided by c-ares can be used in a program.

       This function must be called at least once within the life of a  program,  before  the  program  actually
       executes any other c-ares library function.  Initializations done by this function remain effective until
       a number of calls to ares_library_cleanup(3) equal to the number of calls to this function are performed.

       Successive  calls  to  this  function  do  nothing further, only the first call done when c-ares is in an
       uninitialized state is actually effective.

       The flags parameter is a bit pattern that tells c-ares exactly which features should be  initialized,  as
       described  below.  Set  the  desired  bits  by  ORing the values together. In normal operation you should
       specify ARES_LIB_INIT_ALL. Don't use any other value unless you  are  familiar  with  it  and  trying  to
       control some internal c-ares feature.

       The  ares_library_init_mem  function allows the caller to provide memory management functions that the c-
       ares library will be use instead of malloc(3), free(3) and realloc(3).

       This function is not thread safe.  You have to call it once the program has started, but this  call  must
       be  done  before the program starts any other thread. This is required to avoid potential race conditions
       in library initialization, and also due to the fact that ares_library_init(3) might call  functions  from
       other  libraries  that  are thread unsafe, and could conflict with any other thread that is already using
       these other libraries.

       On Windows platforms, the library user should ensure  that  WSAStartup()  is  called  before  the  c-ares
       library is initialized and used.

       Win32/64  application  DLLs  shall not call ares_library_init(3) from the DllMain function. Doing so will
       produce deadlocks and other problems.

FLAGS

       ARES_LIB_INIT_ALL
            Initialize everything possible. This sets all known bits.

       ARES_LIB_INIT_WIN32
            Initialize Win32/64 specific libraries.  As of c-ares 1.19.0,  this  is  ignored  as  there  are  no
            currently dynamically loaded libraries.

       ARES_LIB_INIT_NONE
            Initialize nothing extra. This sets no bit.

RETURN VALUE

       Upon  successful  completion,  ares_library_init(3)  returns  0.   Otherwise,  a non-zero error number is
       returned to indicate the error. Except for ares_strerror(3), you shall not call any other c-ares function
       upon ares_library_init(3) failure.

AVAILABILITY

       This function was first introduced in c-ares version 1.7.0 along  with  the  definition  of  preprocessor
       symbol  CARES_HAVE_ARES_LIBRARY_INIT as an indication of the availability of this function. Its recursive
       behavior, which requires a matching number of calls to ares_library_cleanup(3) in order  to  deinitialize
       the  library,  is present since c-ares version 1.10.0. Earlier versions would deinitialize the library on
       the first call to ares_library_cleanup(3).

       Since the introduction of this function it is absolutely mandatory to call it for  any  Win32/64  program
       using c-ares.

       Non-Win32/64  systems  can still use c-ares version 1.7.0 without calling ares_library_init(3) due to the
       fact that currently it is nearly a do-nothing function on non-Win32/64 platforms at this point.

SEE ALSO

       ares_library_cleanup(3), ares_strerror(3)

AUTHOR

       Yang Tse

       Copyright 1998 by the Massachusetts Institute of Technology.
       Copyright (C) 2004-2009 by Daniel Stenberg.

                                                   19 May 2009                              ARES_LIBRARY_INIT(3)