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List:       wine-devel
Subject:    Re: [PATCH 2/7] msvcrt: Clean up registered C++ object in handler.
From:       Piotr Caban <piotr.caban () gmail ! com>
Date:       2017-05-31 9:48:44
Message-ID: 42c616a7-ec6b-cab9-c270-10f342b39c18 () gmail ! com
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On 05/31/17 00:59, Daniel Lehman wrote:
> 
> On 05/24/17 02:55, Daniel Lehman wrote:
> > +static DWORD cxx_catch_cleanup(EXCEPTION_RECORD *rec, \
> > EXCEPTION_REGISTRATION_RECORD *frame, +                               CONTEXT \
> > *context, +EXCEPTION_REGISTRATION_RECORD **pdispatcher) {
> > +    if (rec->ExceptionFlags & (EH_UNWINDING | EH_EXIT_UNWIND))
> > +    {
> > +        thread_data_t *data = msvcrt_get_thread_data();
> > +        frame_info *cur;
> > +
> > +        if (cxx_is_consolidate(rec))
> > Is this condition really needed? Shouldn't we clean the object no matter what's \
> > the reason of unwind?
> 
> Yeah.  That's covered by patch 7/7.  The original code only cleaned up if \
> consolidating. 
> Since this 2/7 patch was somewhat of a refactoring for the later patches, I kept \
> the consolidate-only cleanup logic.  I can merge them if you want
Yes, it would be preferable to merge the patches.

> > > +                if ((ULONG64)cur <= (ULONG64)frame)
> > This condition is not working. It's making assumption about order of catch_frame \
> > and frame_info variables on stack while they are declared this way:
> 
> I see what you mean.  If I forcefully reverse them, my tests crash;  my version of \
> gcc was always putting them in the same place on the stack, regardless of where \
> they were declared 
> > > +    EXCEPTION_REGISTRATION_RECORD catch_frame;
> > > cxx_frame_info frame_info;
> > Shouldn't the cxx_catch_cleanup just unregister the object that was registered in \
> > call_catch_block >
> I didn't find a way to be call __CxxUnregisterObject on that one specifically (I'll \
> try suggestions if you got em)
I think that the easiest solution would be to define something like:
struct catch_cleanup_frame {
     EXCEPTION_REGISTRATION_RECORD frame;
     cxx_frame_info frame_info;
}
and just call __CxxUnregisterObject with passed 
catch_cleanup_frame->frame_info in handler.

> > Here's a test case that demonstrate the problem with cur <= frame
> > comparison:
> > 
> > 	try {
> > 		try { int *p = NULL; *p = 0x42; }
> > 		catch (klass x) { throw 1; }
> > 	} catch (int i) { }
> > 
> > 	try { throw 1; }
> > 	catch(...) {}
> 
> This crashes for me even on Windows because the SEGV is uncaught.  It 'works' if I \
> set an seh translator that throws int, but I get identical results on Wine with my \
> series applied.  Do I need to add something?
It was meant to be run with seh translator set. It might be 
compiler/optimization level specific. On my computer it leads to 
incorrect stack usage caused by "cur <= frame" condition. The 
__CxxUnregisterObject is not called in my case and the registered 
objects list points to invalid stack space.

Thanks,
Piotr


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