Yes I saw those but those didn't do the trick :( or my understanding of
how to use these macros is wropng. Maybe I should have left that code in
the example ...
I tried:
void releaseRef() {
ANNOTATE_HAPPENS_BEFORE(&m_nRefCnt);
int nRefCnt = __sync_add_and_fetch(&m_nRefCnt, -1);
if (nRefCnt == 0) {
ANNOTATE_HAPPENS_AFTER(&m_nRefCnt);
delete this;
}
}
I did get the race condition suppressed in some cases by using
VALGRIND_HG_DISABLE_CHECKING / VALGRIND_HG_ENABLE_CHECKING
The problem there is that I do not know the sizeof() the instantiated
object the smart-pointer refers to. Aka if the interitance hierarchy is
C isa B isa A and I have a smartpointer to B then I do not now that the
actual object isa C. I need to know it isa C because that changes the
location of where the vtable-pointer of A is stored. This is especially
the case when I have multiple inheritance that all share the same base.
I think the problem is not with the refcounting, but with the virtual
inheritance. Or, formulated as question, what is the difference between
the generated code with virtual and non-virtual inheritance, and how
does that explain the race condition?
I made an assembly-dump of both the compilations to see whether those
could support my theory of stuff happening after the releaseRef call. I
have an almost negligible knowledge of assembly, but I think that the
generated assembly does not show any instructions after the call to
releaseRef, but just some more instructions before the call.
At the moment I'm not able to post these, but will do if desired. You
can generated them yourselfs using the -S flag, something like:
g++ -g -DINHERIT="public" -S refcnttst.cc -o refcnttst.s
g++ -g -DINHERIT="virtual public" -S refcnttst.cc -o refcnttst-virt.s
regards,
Joris
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