registers the given
to be called at program exit, whether via
or via return from the program's
Functions so registered are called in reverse order;
no arguments are passed.
These functions must not call
if it should be necessary to terminate the process while in such a
function should be used.
(Alternatively, the function may cause abnormal
process termination, for example by calling
At least 32 functions can always be registered,
and more are allowed as long as sufficient memory can be allocated.
function behaves identically to
except that it takes a block, rather than a function pointer.