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This was resulting in memory leak warnings from Valgrind, which were getting in the way of debugging an unrelated uninitialized memory issue. We normally wouldn't care about this sort of bounded memory leaks, but in this case Valgrind can't tell if the memory leak is from the runner or filesystem, errors, and prevents other tests from running. Just to be more annoying, this only triggered when overriding defines, which is something you do exactly when you are trying to debug something. Fortunately, with a bit of typecasting we still have access to the allocated value arrays (type-stripped due to opaque test_define_t), and can clean up the relevant memory.