NAME¶
ares_library_cleanup - c-ares library deinitialization
SYNOPSIS¶
#include <ares.h>
void ares_library_cleanup(void)
cc file.c -lcares
DESCRIPTION¶
The
ares_library_cleanup function uninitializes the c-ares library,
freeing all resources previously acquired by
ares_library_init(3) when
the library was initialized, provided there was only one single previous call
to
ares_library_init(3). If there was more than one previous call to
ares_library_init(3), this function uninitializes the c-ares library
only if it is the call matching the call to
ares_library_init(3) which
initialized the library (usually the very first call to
ares_library_init(3)). Other calls to
ares_library_cleanup(3)
have no effect other than decrementing an internal counter.
This function must be called when the program using c-ares will no longer need
any c-ares function. Once the program has called
ares_library_cleanup(3) sufficiently often such that the library is
uninitialised, it shall not make any further call to any c-ares function.
This function does not cancel any pending c-ares lookups or requests previously
done. Program must use
ares_cancel(3) for this purpose.
This function is not thread safe. You have to call it once the program is
about to terminate, but this call must be done once the program has terminated
every single thread that it could have initiated. This is required to avoid
potential race conditions in library deinitialization, and also due to the
fact that
ares_library_cleanup(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_cleanup(3) from the
DllMain function. Doing so will produce deadlocks and other problems.
AVAILABILITY¶
This function was first introduced in c-ares version 1.7.0 along with the
definition of preprocessor symbol
CARES_HAVE_ARES_LIBRARY_CLEANUP as an
indication of the availability of this function. Reference counting in
ares_library_init() and
ares_library_cleanup(), which requires
calls to the former function to match calls to the latter, 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_cleanup(3) due to the fact that
currently it is
nearly a do-nothing function on non-Win32/64 platforms.
SEE ALSO¶
ares_library_init(3), ares_cancel(3)
AUTHOR¶
Yang Tse
Copyright 1998 by the Massachusetts Institute of Technology.
Copyright (C) 2004-2009 by Daniel Stenberg.