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
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. Dont use any other value unless you are
familiar with it and trying to control some internal c-ares feature.
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.
Win32/64 application DLLs shall not call ares_library_init(3) from the
DllMain function. Doing so will produce deadlocks and other problems.
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
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.