[Dune] [#779] test-ug fails, apparently to to allocator problems in the GenericGeometries

[Dune]

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FS#779 - test-ug fails, apparently to to allocator problems in the GenericGeometries
User who did this - Martin Nolte (nolte)

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The bug might have arisen only after the allocator change, but actually it was caused by calling setup too often. Let me explain:
A geometry object has to provide memory for, e.g., the jacobian matrices. It is explicitly allowed that an application calls jacobianInverseTransposed for a certain point once and reuses the returned reference until it requires the jacobianInverseTransposed for another point. Now, when creating a generic geometry, this memory is freshly allocated from the heap (or whereever the allocator obtains it from). Assigning another generic geometry to it will yield a new object, invalidating the reference to the jacobianInverseTransposed.
What happened in UG was the following: Each time an intersection's geometry was requested, the geometry was reassigned. You may argue that the user will only call geometry() once, so there is no problem. But: The integrationOuterNormal internally called the method, too. And this call made the gridcheck read from an invalid memory address.
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More information can be found at the following URL:
http://www.dune-project.org/flyspray/index.php?do=details&task_id=779#comment1981

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