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Re: [PATCH] c++/58796 Make nullptr match exception handlers of pointer type


On 15/07/16 22:53 +0100, Jonathan Wakely wrote:
On 15/07/16 23:36 +0200, Jakub Jelinek wrote:
On Fri, Jul 15, 2016 at 10:07:03PM +0100, Jonathan Wakely wrote:
+      if (typeid (*this) == typeid(__pointer_type_info))
+        {
+          *thr_obj = nullptr;
+          return true;

But you have the above store too.

That doesn't write to the exception object, it only does a single
dereference (compared to the double dereference of the racy write), so
it writes to the local variable in the PERSONALITY_FUNCTION in
eh_personality.cc

So that shouldn't race with other threads. I think.


TSan agrees. When I compile my test and yours (and include
libsupc++/pbase_type_info.cc in the executable, so the writes are also
instrumented by tsan) then I see races for the *(ptrdiff_t*)*thr_obj
writes but not the *thr_obj ones.

It's only the ptr-to-data-member case that scribbles in the actual
exception object.



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