### Author:  [@jsemeda](https://discourse.vtk.org/u/jsemeda)
#### Post date: [July 3, 2026, 9:25pm UTC](https://discourse.vtk.org/t/unresolved-external-symbol-void-cdecl-vtkrenderingvolume-autoinit-construct-void/16478/1 "2026-07-03T21:25:39Z")
I am getting this error, vtk-9.5, static libs build with VS under WIndows10.
I googled the issue, AI suggested that VTK uses dynamic linking to link the rendering backend at runtime and with static linking that does not take place. It suggested I add these lines to the file where the rendering code is
#include \
VTK\_MODULE\_INIT(vtkRenderingOpenGL2);
VTK\_MODULE\_INIT(vtkRenderingVolume);
I did and that did not work. The next thing was to add these preprocessor directives:
vtkRenderingOpenGL2\_AUTOINIT=1(vtkRenderingGL2PSOpenGL2) vtkVolumeRenderingOpenGL2\_AUTOINIT=1(vtkRenderingVolumeOpenGL2)
It did not work too.
Any ideas how to fix this issue?
---
### Author:  [@sankhesh](https://discourse.vtk.org/u/sankhesh)
#### Post date: [July 5, 2026, 6:46pm UTC](https://discourse.vtk.org/t/unresolved-external-symbol-void-cdecl-vtkrenderingvolume-autoinit-construct-void/16478/2 "2026-07-05T18:46:16Z")
Hi @jsemeda đź‘‹. Could you please share the CMake flags used to build VTK? Also, the error is not visible in the original post. Could you please reshare?
---
### Author:  [@ben.boeckel](https://discourse.vtk.org/u/ben.boeckel)
#### Post date: [July 20, 2026, 5:05pm UTC](https://discourse.vtk.org/t/unresolved-external-symbol-void-cdecl-vtkrenderingvolume-autoinit-construct-void/16478/3 "2026-07-20T17:05:13Z")
I think your edits are in the right direction, but you also need to link to the targets involved in providing those factories. You’re probably missing a [`vtk_module_autoinit` call](https://docs.vtk.org/en/latest/api/cmake/ModuleSystem.html#autoinit) in your CMake code.
---
### Author:  [@jsemeda](https://discourse.vtk.org/u/jsemeda)
#### Post date: [August 3, 2026, 2:26am UTC](https://discourse.vtk.org/t/unresolved-external-symbol-void-cdecl-vtkrenderingvolume-autoinit-construct-void/16478/4 "2026-08-03T02:26:56Z")
How should I do that? Does attaching the cmake file here help?
The full error is :
error LNK2019: unresolved external symbol “void \_\_cdecl vtkVolumeRenderingOpenGL2\_AutoInit\_Construct(void)” (?vtkVolumeRenderingOpenGL2\_AutoInit\_Construct@@YAXXZ) referenced in function “public: \_\_cdecl `anonymous namespace’::vtkVolumeRenderingOpenGL2\_ModuleInit::vtkVolumeRenderingOpenGL2\_ModuleInit(void)” (??0vtkVolumeRenderingOpenGL2\_ModuleInit@?A0x43c0deb8@@QEAA@XZ)
---
### Author:  [@jsemeda](https://discourse.vtk.org/u/jsemeda)
#### Post date: [August 3, 2026, 3:54am UTC](https://discourse.vtk.org/t/unresolved-external-symbol-void-cdecl-vtkrenderingvolume-autoinit-construct-void/16478/5 "2026-08-03T03:54:04Z")
I added
# Enable auto-initialization for the target and modules
vtk\_module\_autoinit(
TARGETS MyVTKApp
MODULES ${VTK\_LIBRARIES}
)
but it did not help. I tried replacing the ${VTK\_LIBRARIES} with the missing module name from the error, vtkVolumeRenderingOpenGL2, but it gave an error in the cmake file.
---
### Author:  [@jsemeda](https://discourse.vtk.org/u/jsemeda)
#### Post date: [August 3, 2026, 4:12am UTC](https://discourse.vtk.org/t/unresolved-external-symbol-void-cdecl-vtkrenderingvolume-autoinit-construct-void/16478/6 "2026-08-03T04:12:06Z")
I also tried
vtk\_module\_autoinit(
TARGETS dicom2meshlib
MODULES vtk::CommonCore
vtk::RenderingCore
vtk::RenderingOpenGL2
vtk::RenderingVolume
vtk::RenderingVolumeOpenGL2
vtk::InteractionStyle
)
did not work. I am following what is in the documentaion, but maybe the way I am listing the modules is not correct? Maybe the module names? although when I write this in the cmake file the autocomplete is listing these modules as written.
---
### Author:  [@jaswantp](https://discourse.vtk.org/u/jaswantp)
#### Post date: [August 3, 2026, 1:37pm UTC](https://discourse.vtk.org/t/unresolved-external-symbol-void-cdecl-vtkrenderingvolume-autoinit-construct-void/16478/7 "2026-08-03T13:37:26Z")
I’ve seen this in the past when devs try to write the module init themselves and fumble on the module names.
> vtkVolumeRenderingOpenGL2\_AUTOINIT=1(vtkRenderingVolumeOpenGL2)
You’ve transposed the module name. It should be `vtkRenderingVolumeOpenGL2_AUTOINIT=...` That might explain why you saw `error LNK2019: unresolved external symbol “void __cdecl vtkVolumeRenderingOpenGL2_AutoInit_Construct`.
When you tried autoinit, did you remove the manual module init and try again? Maybve stale `VTK_AUTOINIT` define in cache/add\_definitions from incorrect build is being carried forward. Try to delete your build directory and re-configure from scratch using the autoinit.
What I can suggest to you is don’t hand-write VTK\_MODULE\_INIT / VTK\_AUTOINIT defines. Let CMake do it. Call `find_package` with the components you need. They will be placed in `VTK_LIBRARIES`
```c
# CMakeLists.txt
find_package(VTK REQUIRED COMPONENTS
CommonCore
InterationStyle
RenderingCore
RenderingVolume
RenderingVolumeOpenGL2
RenderingOpenGL2
)
target_link_libraries(dicom2meshlib PRIVATE ${VTK_LIBRARIES}) # needed
vtk_module_autoinit(TARGETS dicom2meshlib MODULES ${VTK_LIBRARIES}) # also needed
```