missing-intent (C061)

This rule is turned on by default.

What it does

Checks for missing intent on dummy arguments

Why is this bad?

Procedure dummy arguments should have an explicit intent attributes. This can help catch logic errors, potentially improve performance, as well as serving as documentation for users of the procedure.

Arguments with intent(in) are read-only input variables, and cannot be modified by the routine.

Arguments with intent(out) are output variables, and their value on entry into the routine can be safely ignored -- technically, they become undefined on entry, which includes deallocation and/or finalisation.

Finally, intent(inout) arguments can be both read and modified by the routine. If an intent is not specified, it will default to essentially intent(inout) -- however, this can be dangerous if passing literals or expressions that can't be modified.

This rule will permit the absence of intent for dummy arguments that include the value attribute. It will also permit pointer dummy arguments that lack an intent attribute in standards prior to Fortran 2003, in which pointer dummy arguments were not allowed to have intent.