I read on many posts on Stack Overflow that an allocatable array is deallocated when it is passed in a subroutine where the dummy argument is intent(out).
If I consider the following code :
program main
real, dimension(:), allocatable :: myArray
integer :: L=8
allocate(myArray(1:L))
call initArray(myArray)
print *, myArray
contains
subroutine initArray(myArray)
real, dimension(:), intent(out) :: myArray
myArray(:) = 10.0
end subroutine initArray
end program main
the output is right. So, when deallocation occurs, memory is released but the array shape is kept. Is it exact ? Any detailed explanation would be appreciated.
I read different posts on the subject (Can I use allocatable array as an intent(out) matrix in Fortran?, What is the effect of passing an allocatable variable into a subroutine with non-allocatable argument?, ...). So I understand that the array is deallocated but I would like to understand what does it mean because in my code, the size is kept and I am also surprised that this code works.
You are slightly misunderstanding what happens here.
Arrays which are deallocated on entry to a procedure with intent(out) are those allocatable arrays which correspond to an allocatable dummy.
What intent(out) means for an argument depends entirely on the characteristics of the dummy not actual argument.
Allocatable actual arguments which correspond to ordinary dummy arguments are not deallocated. (If they were, the dummy argument which is not allocatable would have to be not allocated!)
Instead, the allocation status of the actual argument remains unchanged and the shape of the assumed (not deferred) shape dummy argument remains the same.
The dummy argument becomes undefined, as an intent(out). For the ordinary dummy argument here, that refers simply to its value (which is immediately defined in that assignment statement).