Question

According to the Fortran standards information I could find (F77,F90/95) an array declarator where there is no lower bound assumes that this lower bound is 1. As the upper bound needs to be larger than or equal to the lower bound, this would make the following statement not allowed:

INTEGER A(0)

However, I cannot make ifort nor gfortran complain in any way about that statement. Is the compiler not required to flag this as an error?

Answer 1

As the upper bound needs to be larger than or equal to the lower bound, this would make the following statement not allowed.

From Fortran 2008 Standard:

5.3.8.2 Explicit-shape array
[…]
3 The values of each lower-bound and upper-bound determine the bounds of the array along a particular dimension and hence the extent of the array in that dimension. If lower-bound appears it species the lower bound; otherwise the lower bound is 1. The value of a lower bound or an upper bound may be positive, negative, or zero. The subscript range of the array in that dimension is the set of integer values between and including the lower and upper bounds, provided the upper bound is not less than the lower bound. If the upper bound is less than the lower bound, the range is empty, the extent in that dimension is zero, and the array is of zero size.