For optimisation reasons, Fortran enforces that the dummy arguments of a subroutine or function are not alias, i.e., they do not point the the same memory place.
I am wondering if the same constraint applies to the returned value of a function. In other words, for a given myfunc function:
function myfunc(a)
real, intent(in) :: a(:)
real :: myfunc(size(a))
myfunc = a * 2
end function myfunc
is it standard-compliant to write: a = myfunc(a) and b = myfunc(a) ?
The arguments of a function and function return value are different things. Contrary the previous answer, the functional arguments ARE passed by reference, or by copy-in copy-out, unless they are declared as dummy arguments with the VALUE attribute. This is a major difference of Fortran vs. C.
However, if the function value is constructed by normal assignment (=) and not by pointer assignment (=>) they are separate entities. In your code, the value of myfunc is got by copying the value of a. Therefore no standard rules are broken by a = myfunc(a) or b = myfunc(a).