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.

       ARES_LIB_INIT_NONE
            Initialize nothing extra. This sets no bit.

RETURN VALUE

       Upon successful completion, ares_library_init() will  return  0.   Otherwise,  a  non-zero
       error  number  will  be  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()  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().

       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)