Comment (by Roland Haas):

A (partial) workaround would be to test for the faulty behaviour in configure, set a #define and use that with an #ifdef to enable the workarounds only when and if needed. This would let Cactus (but not CarpetX) be used on old systems just like now but those who want to try at the new CarpetX code will have to make sure to use modern compilers (have to any since it requires C++17). Also see

#2409 about affected systems being retired.

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Ticket URL: https://bitbucket.org/einsteintoolkit/tickets/issues/2407/cactus-math-work-arounds-break-carpetx