Cactus passes Fortran code (at least with extensions .F77 .F and .F90) through the C preprocessor in FPP passing FPPFLAGS.

This cpp must use traditional (pre-ANSI) behaviour, ie be string and not token based to preserve whitespace in Fortran fixed format code and handle concatenation using FOO/**/BAR correctly.

Getting this wrong by setting eg only FPP in an option list results in strange error messages.

Cactus' configure should check that FPP and FPPFLAGS behave as expected. Eg by processing:

TRAD/**/ITIONAL

which produces:

TRADITIONAL

with --traditional and

TRAD ITIONAL

without, so one can grep for the expected string.

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Ticket URL: https://bitbucket.org/einsteintoolkit/tickets/issues/2566/check-for-traditional-in-fpps-behaviour