Hello! I've done some more research on this particular bug.
> > > I have an impression that it has to do with the bug I previously reported
> > > (and someone here claimed he could reproduce it)
> >
> > Please provide a link to the Cygwin ML message; is it this, confirmed by
> > Takashi
> > Yano:
> >
> > https://cygwin.com/ml/cygwin/2019-10/msg00038.html
>
> Yes, that one.
So, first of all, _GCC_specific_handler() inside libgcc never returns anything
but ExceptionContinueSearch . However it's clear from __cxa_throw() code that
the control must go past RaiseException() in order to reach std::terminate().
Study of 32-bit version behavior with gdb confirms that indeed this is the
expected control flow.
So, i conclude that ExceptionContinueExecution should be issued somewhere
else. Again, with gdb and grep i've figured out that exception::handle() inside
cygwin1.dll is responsible for it. Here is where behavior significantly differs
between 64 and 32-bit versions. With 32-bit version the exception handling ends
here:
--- cut ---
#ifdef __i386__
if (me.andreas)
me.andreas->leave (); /* Return from a "san" caught fault */
#endif
--- cut ---
leave() never returns, the exception gets re-thrown a couple of times (every
time ending up in this leave()), then RaiseException() eventually returns and
std::terminate() is called.
With x68-64 version it seems to go through switch (e->ExceptionCode) and
return ExceptionContinueSearch from "default" case. There are no more handlers,
so the process is terminated. ExceptionCode is 0x20474343 (" GCC" ?)
Apparently there's something missing and/or not working regarding this "san
Andreas" trick. I don't know what it is and have no time to research since i'm
leaving for vacation till January.So won't be responsive for some time, sorry.
Hopefully my study will give you some hints.
Kind regards,
Pavel Fedin
Senior Engineer
Samsung Electronics Research center Russia
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