topic DEBUG ifx VS2022 watch class variable in Intel® Fortran Compiler

DEBUG ifx VS2022 watch class variable

Haku — Tue, 23 Dec 2025 12:54:07 GMT

Environment

Visual Studio 2022 : 17.14.21

IFX : 2025.3.0

Problem

In debug mode, Visual Studio cannot display correct Watch values for a polymorphic (class) allocatable array.

type :: Layer !... end type Layer type extends(Layer):: extended_Layer !... end type extended_Layer class(layer),allocatable,dimension(:):: L allocate(extended_Layer::L(5))

situation 1
Right after allocation, I cannot inspect L correctly in the Watch window.

situation 2
Even if I use select type, I still can’t inspect the variable properly inside the type is block:

select type (L) type is (extended_Layer) ! ... end select

The Watch window shows an incorrect upper bound for L (e.g., -1) as below, although print statements show the correct values at runtime.

Does this mean IFX + Visual Studio currently cannot reliably display polymorphic (class) variables in Watch?
If so, is the recommended workaround to use print statements, or to pass the object into a subroutine with a non-polymorphic dummy argument?

Thanks in advance.

Re: DEBUG ifx VS2022 watch class variable

JohnNichols — Sat, 27 Dec 2025 17:36:49 GMT

I watch this forum, mainly because of the neat people.

Your question is interesting, but it would help if it was a complete small program so I could put it into a sln and run it. I am not going to make the program.

Re: DEBUG ifx VS2022 watch class variable

Haku — Fri, 09 Jan 2026 07:16:42 GMT

Thanks for your reply, and I'm sorry for the late follow-up.

I'll share a simple program below-just copy/paste it into an empty Fortran project and it should run.

module simple_class implicit none(external) private public :: basic_layer, advanced_layer,alayer_1 type basic_layer integer :: layer_id double precision:: dx,dy end type basic_layer type ,extends(basic_layer) :: advanced_layer double precision :: dz end type advanced_layer class(basic_layer),allocatable :: alayer_1(:) contains end module simple_class program main use simple_class,only: advanced_layer,basic_layer,alayer_1 type(basic_layer) :: layer1 type(advanced_layer) :: layer2 class(basic_layer),allocatable :: layer3,layer4 !===successful watcher debug session=== layer1%layer_id = 1 layer1%dx = 0.1d0;layer1%dy = 0.2d0 continue layer2%layer_id = 2 layer2%dx = 0.3d0;layer2%dy = 0.4d0;layer2%dz = 0.5d0 continue allocate(basic_layer::layer3) select type(layer3) ! to confirm the dynamic type type is (basic_layer) layer3%layer_id = 3 layer3%dx = 0.6d0;layer3%dy = 0.7d0 end select continue allocate(advanced_layer::layer4) select type(layer4) ! to confirm the dynamic type type is(advanced_layer) layer4%layer_id = 4 layer4%dx = 0.8d0;layer4%dy = 0.9d0;layer4%dz = 1.0d0 print *, "layer4%dz =", layer4%dz end select continue !===successful watcher debug session=== !===failure watcher debug session=== allocate(advanced_layer::alayer_1(3)) select type(alayer_1) ! to confirm the dynamic type type is(advanced_layer) alayer_1(:)%layer_id = 5 alayer_1(:)%dx = 1.1d0;alayer_1(:)%dy = 1.2d0;alayer_1(:)%dz = 1.3d0 print *, "alayer_1(1)%dz =", alayer_1(1)%dz end select continue !===failure watcher debug session=== !===successful watcher debug session=== !-use block to see the content test : block type(advanced_layer) :: aLayer(3) select type(alayer_1) ! to confirm the dynamic type type is (advanced_layer) aLayer = alayer_1 end select continue end block test !===successful watcher debug session=== end program main

As shown in comments:

If I define a variable as type(layer1,layer2) or as a scalar class (layer3,layer4), it can be inspected correctly in the debug Watch window.
However, when I define an array of class, the Watch failed and shows stange values (like in the picture below).

For now, the only workaround I have is the last "block" part: by assigning an element into a specific type variable (aLayer),I can watch this aLayer variable to check the original variable. But it's tedious to insert this block everywhere just for debugging.
Is it simply hard(or unsupported) for the debugger to inspect an array of class objects? Even though the OOP part in fortran attract me a lot.
Thanks in advance!

Re: DEBUG ifx VS2022 watch class variable

JohnNichols — Sat, 10 Jan 2026 16:44:01 GMT

I cannot see the variables and it crashes the debugger, your method will work it is not elegant, and in pure math not elegant is the kiss of death.

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Re: DEBUG ifx VS2022 watch class variable

Haku — Sun, 11 Jan 2026 09:50:28 GMT

Thank you for your interesting suggestion.
As a result, since the debugger has trouble inspecting arrays of class objects, I decided to use a preprocessor-based approach to the basic type so that it can be inspected in the watch window.

Have a nice day!!