__cxa_finalize and `on_exit'

[Jason Merrill]

>>>>> Martin von Loewis <loewis at informatik.hu-berlin.de> writes:

 > Then, of course, the question is how to run the __cxa_atexit list at
 > the end of the program. To do so, the proposal is to put a
 > __cxa_finalize call into the .fini section.

 > Unfortunately, it seems that this approach breaks the case when you do
 > integrate the C and C++ libraries; in this case, the extra call gets
 > in the way of extern "C" atexit processing, which must be placed into
 > the runtime system very cautiously.

How so?  I would think you could just register __cxa_finalize (NULL) (or
equivalent) with the C atexit.  Then exit runs all the destructors, and the
calls in .fini do nothing, because everything has already been
deregistered.  The atexit chain is run before .fini stuff, I'm pretty sure.

 > My proposal: it is left unspecified by the ABI how exactly the
 > __cxa_atexit list is invoked - whoever provides the implementation of
 > __cxa_atexit and __cxa_finalize is also responsible for having the
 > finalizers called at the right point in time (i.e. as a result of
 > std::exit invocation).

That won't work; anything that involves .fini must be specified by the ABI.

Jason