Comment (by Erik Schnetter):

Access checking should instead done by the driver when it calls a scheduled function. Before the call, the driver fills in cctkGH with the pointers to all (!) variables and time levels. Checking access there would be straightforward (in Carpet and CarpetX, not in PUGH), and would also be cheaper since group-wise calculations have to be done only once per group, not once per variable. CCTK_VarDataPtrI would then simply look up the pointer in cctkGH, with proper index checking. The latter could also be avoided if we trust the driver.

The checked macros also call CCTK_VarDataPtrI.

Overall, this would reduce overhead both in the driver an in the flesh.

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Ticket URL: https://bitbucket.org/einsteintoolkit/tickets/issues/2512/enable-detection-of-attribute-pure