cctk_Loop.h used constructs like

#define FOO(x) cctk_loop_/**/x

to concatenate identifier names. This only works when using cpp --traditional but not for an ANSI C preprocessor that requires

#define FOO(x) cctk_loop ## x

Cactus’s old header files in cctk_Types.h support both options via an ifdef.

All current option lists use cpp --traditional for FPP and Cactus’s linux built in architecture file does the same, and cctk_Loop.h is (as of 2020-04-03) broken for other reasons (see http://lists.einsteintoolkit.org/pipermail/users/2020-February/007298.html) so this issue has not yet show up.

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Ticket URL: https://bitbucket.org/einsteintoolkit/tickets/issues/2363/make-cctk_looph-work-in-fortran-even-if-an