# Confused by finalization behaviour **URL:** \ **Category:** Help\ **Created:** [October 15, 2024, 4:57am UTC](https://fortran-lang.discourse.group/t/confused-by-finalization-behaviour/8720 "2024-10-15T04:57:57Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![Blaise](https://avatars.discourse-cdn.com/v4/letter/b/ecae2f/32.png) [@Blaise](https://fortran-lang.discourse.group/u/Blaise)\ **Post date:** [October 15, 2024, 4:57am UTC](https://fortran-lang.discourse.group/t/confused-by-finalization-behaviour/8720/1 "2024-10-15T04:57:57Z")
Hi, I am having a hard time understanding the behaviour of finalization. See the attached small code: [LinAlg1.F90](https://fortran-lang.discourse.group/uploads/short-url/2xETkEXKC4iSNr0OuQMd0gwF5U6.F90) (2.2 KB) Here is the output when running on an arm Mac with gfortran 14.2 ( I get a similar output under linux with the most recent intel compilers). ```auto sibookpro:LinAlg_Class $ ./LinAlg1 Destroying empty No need to deallocate empty%data Destroying u Deallocating u%data Viewing u 1.00000000 2.00000000 3.00000000 ... 3.00000000 Destroying u Deallocating u%data Destroying empty No need to deallocate empty%data Destroying v Deallocating v%data Viewing v 2.33999991 2.33999991 2.33999991 ... 2.33999991 ``` Why is finalization called _twice_ during creation? ---
**Author:** ![davidpfister](https://yyz2.discourse-cdn.com/free1/user_avatar/fortran-lang.discourse.group/davidpfister/32/3949_2.png) [@davidpfister](https://fortran-lang.discourse.group/u/davidpfister)\ **Post date:** [October 15, 2024, 5:19am UTC](https://fortran-lang.discourse.group/t/confused-by-finalization-behaviour/8720/2 "2024-10-15T05:19:32Z")
Hi @Blaise, When you use a function constructor, you return an object that serves as a rhs in your assignment ```auto u = LinAlg_Type('u',x) ``` That object is very short lived and will be finalized once the lhs is allocated/assigned. If you do not want to get this behavior you need to use subroutine constructors with intent out arguments. You can have a look at this [discussion](https://fortran-lang.discourse.group/t/finalization-ifort-vs-gfortran/7816/11). You will probably find some more details about ‘final’ ---
**Author:** ![grofz](https://avatars.discourse-cdn.com/v4/letter/g/8797f3/32.png) [@grofz](https://fortran-lang.discourse.group/u/grofz)\ **Post date:** [October 15, 2024, 5:27am UTC](https://fortran-lang.discourse.group/t/confused-by-finalization-behaviour/8720/3 "2024-10-15T05:27:16Z")
When the following statement is called u = LinAlg\_Type(‘u’,x) actually two things occur: 1. the code inside the function is executed, operating with the internal variable that the function “returns” 2. assignment from this internal returning variable to the variable “u” declared within main program takes place. So the “u” is finalized first (before the assignment), the second call is for finalizing the internal variable inside the function. It helps to realize that when inside the function, the function is not working with the variable “u” because the function “does not know” what happens with the result (It could be used, for example, as an intermmediate in an expression). ---
**Author:** ![jwmwalrus](https://yyz2.discourse-cdn.com/free1/user_avatar/fortran-lang.discourse.group/jwmwalrus/32/4483_2.png) [@jwmwalrus](https://fortran-lang.discourse.group/u/jwmwalrus)\ **Post date:** [October 15, 2024, 9:13am UTC](https://fortran-lang.discourse.group/t/confused-by-finalization-behaviour/8720/4 "2024-10-15T09:13:11Z")
> [@Blaise](#): > > I am having a hard time understanding the behaviour of finalization. Adding to what others said: Notice that, since you’re not using pointers, you don’t really need to worry about providing a `final` procedure. The `allocatable` attribute implies automatic deallocation of any item when it goes out of scope. ---
**Author:** ![PierU](https://yyz2.discourse-cdn.com/free1/user_avatar/fortran-lang.discourse.group/pieru/32/1848_2.png) [@PierU](https://fortran-lang.discourse.group/u/PierU)\ **Post date:** [October 15, 2024, 11:27am UTC](https://fortran-lang.discourse.group/t/confused-by-finalization-behaviour/8720/5 "2024-10-15T11:27:58Z")
> [@grofz](#): > > u = LinAlg\_Type(‘u’,x) > actually two things occur: > > 1. the code inside the function is executed, operating with the internal variable that the function “returns” > 2. assignment from this internal returning variable to the variable “u” declared within main program takes place. That’s correct, but note that the compiler is free to optimize this statement, for instance by not creating a temporary object but rather operating directly on `u`. In this case a single finalization would occur. ---
**Author:** ![Blaise](https://avatars.discourse-cdn.com/v4/letter/b/ecae2f/32.png) [@Blaise](https://fortran-lang.discourse.group/u/Blaise)\ **Post date:** [October 15, 2024, 1:34pm UTC](https://fortran-lang.discourse.group/t/confused-by-finalization-behaviour/8720/6 "2024-10-15T13:34:32Z")
Thanks for all the comments. It looks like gfortran does not allow using subroutines for the constructor while ifx throws an unrelated error. See attached. [LinAlg2.F90](https://fortran-lang.discourse.group/uploads/short-url/4B6sOQBiJgummSkSgSCfaYQQuhi.F90) (2.4 KB) ---
**Author:** ![everythingfunctional](https://yyz2.discourse-cdn.com/free1/user_avatar/fortran-lang.discourse.group/everythingfunctional/32/176_2.png) [@everythingfunctional](https://fortran-lang.discourse.group/u/everythingfunctional)\ **Post date:** [October 15, 2024, 1:45pm UTC](https://fortran-lang.discourse.group/t/confused-by-finalization-behaviour/8720/7 "2024-10-15T13:45:43Z")
> [@PierU](#): > > In this case a single finalization would occur. No, the standard says that both finalizations occur. In the case there is a final subroutine that needs to be called then this is not an optimization the compiler is free to make. ---
**Author:** ![PierU](https://yyz2.discourse-cdn.com/free1/user_avatar/fortran-lang.discourse.group/pieru/32/1848_2.png) [@PierU](https://fortran-lang.discourse.group/u/PierU)\ **Post date:** [October 15, 2024, 2:58pm UTC](https://fortran-lang.discourse.group/t/confused-by-finalization-behaviour/8720/8 "2024-10-15T14:58:32Z")
> [@everythingfunctional](#): > > No, the standard says that both finalizations occur. In the case there is a final subroutine that needs to be called then this is not an optimization the compiler is free to make. My bad… I remember there is an assignment case where a finalization can be avoided by a smart compiler, but can’t remember which one. ---
**Author:** ![davidpfister](https://yyz2.discourse-cdn.com/free1/user_avatar/fortran-lang.discourse.group/davidpfister/32/3949_2.png) [@davidpfister](https://fortran-lang.discourse.group/u/davidpfister)\ **Post date:** [October 15, 2024, 3:19pm UTC](https://fortran-lang.discourse.group/t/confused-by-finalization-behaviour/8720/9 "2024-10-15T15:19:42Z")
Indeed, gfortran throws: ```auto In generic interface 'linalg_type' at (1) procedures must be all FUNCTIONs as the generic name is also the name of a derived type ``` In this case, you can simply name your interface LinAlg: ```auto interface LinAlg module procedure LinAlg_constructorArray,LinAlg_constructorLength end interface LinAlg ``` Just check the call in your main program ```auto u = LinAlg_Type('u',x) ``` should become ```auto call LinAlg('u',x, u) ``` And what about using an initialization bound procedure: ```auto type, public :: LinAlg_Type character(len=256) :: name = 'empty' real,dimension(:),allocatable :: data contains procedure, pass(self), private :: LinAlg_constructorArray procedure, pass(self), private :: LinAlg_constructorLength generic, public :: init => LinAlg_constructorArray,LinAlg_constructorLength procedure :: view => LinAlg_view final :: destroy end type ``` that you call like this: ```auto call v%init('v',3,2.34) ```