ares_library_init - c-ares library initialization
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))
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
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.
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
. Don't use any other value unless you are familiar
with it and trying to control some internal c-ares feature.
function allows the caller to provide memory
management functions that the c-ares library will be use instead of
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()
called before the c-ares library is initialized and used.
Win32/64 application DLLs shall not call ares_library_init(3)
DllMain function. Doing so will produce deadlocks and other problems.
- Initialize everything possible. This sets all known
- Initialize Win32/64 specific libraries.
- Initialize nothing extra. This sets no bit.
Upon successful completion, ares_library_init() will return 0. Otherwise, a
non-zero error number will be returned to indicate the error. Except for
, you shall not call any other c-ares function upon
This function was first introduced in c-ares version 1.7.0 along with the
definition of preprocessor symbol CARES_HAVE_ARES_LIBRARY_INIT
indication of the availability of this function. Its recursive behavior, which
requires a matching number of calls to ares_library_cleanup()
to deinitialize the library, is present since c-ares version 1.10.0. Earlier
versions would deinitialize the library on the first call to
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
due to the fact that currently
it is nearly
a do-nothing function on non-Win32/64 platforms at this point.
Copyright 1998 by the Massachusetts Institute of Technology.
Copyright (C) 2004-2009 by Daniel Stenberg.