The GNU Fortran language includes a number of features that are
part of Fortran 90, even when the
-ff90 option is not specified.
The features enabled by
-ff90 are intended to be those that,
-ff90 is not specified, would have another
g77--usually meaning something invalid in the
GNU Fortran language.
So, the purpose of
-ff90 is not to specify whether
to gratuitously reject Fortran 90 constructs.
-pedantic option specified with
-fno-f90 is intended
to do that, although its implementation is certainly incomplete at
-ff90 is specified:
where expr is
is the same type as the real part of expr.
For example, assuming
Z is type
REAL(Z) would return a value of type
not of type
-ff90 is specified.