Comment (by Roland Haas):

Here’s a configure test fragment to trigger the issue:

#include <cmath>
void badmath(void)
{
  using namespace std;
  isnan(0.);
}

to be compiled with icpc -std=c++11 -gxx-name=g++ -O0 -c badmath.cc or g++ -std=c++11 -O0 -c badmath.cc.

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