### Author:  [@pkestene](https://discourse.paraview.org/u/pkestene)
#### Post date: [June 14, 2024, 9:51am UTC](https://discourse.paraview.org/t/cmake-error-when-building-a-paraview-plugin-external-library-linking/14849/1 "2024-06-14T09:51:52Z")
Hello,
I’m writing a C+±based ParaView plugin and found a strange cmake error at generate step.
To reproduce the problem I’m facing, let’s start from a example (e.g. [GitHub - jfavre/ParaViewSalvusPlugin: A C++ plugin for ParaView to read Salvus HDF5 data](https://github.com/jfavre/ParaViewSalvusPlugin)). It builds fine.
Then if I simply add a `target_link_libraries` to library Kokkos, in src/Reader/CMakeLists.txt as shown here:
>
cmake complains with following error message (see below).
What is strange to me is that actually, the Makefiles are well generated; and if I add some code that actually uses Kokkos API, it builds and runs fine; but still this cmake error at generate step persists. I don’t know how to remove it.
I also tried (just for cross-checking) linking to other external third party libraries. It works fine. So I guess there may be something special when linking a paraview plugin to kokkos library ? I don’t know how to investigate that. And again, despite the error message, the plugin can still build ok.
Any help appreciated.
========================================================================
– Found MPI: TRUE (found version “3.1”) found components: C
– Found MPI: TRUE (found version “3.1”)
– Enabled Kokkos devices: OPENMP
– Configuring done
CMake Error in src/CMakeLists.txt:
Evaluation file to be written multiple times with different content. This
is generally caused by the content evaluating the configuration type,
language, or location of object files:
/home/kestenerp/install/visualization/paraview/github/ParaViewSalvusPlugin-pk/\_build/src/CMakeFiles/SalvusHDF5Reader-client-server.Release.args
CMake Error in src/Reader/CMakeLists.txt:
Evaluation file to be written multiple times with different content. This
is generally caused by the content evaluating the configuration type,
language, or location of object files:
/home/kestenerp/install/visualization/paraview/github/ParaViewSalvusPlugin-pk/\_build/src/Reader/CMakeFiles/SalvusHDF5Reader-hierarchy.Release.args
– Generating done
CMake Generate step failed. Build files cannot be regenerated correctly.
---
### Author:  [@ben.boeckel](https://discourse.paraview.org/u/ben.boeckel)
#### Post date: [June 14, 2024, 1:09pm UTC](https://discourse.paraview.org/t/cmake-error-when-building-a-paraview-plugin-external-library-linking/14849/2 "2024-06-14T13:09:19Z")
Your plugin is named the same as the post-`::` part of a module. Rename one of them and it should be fine.
---
### Author:  [@pkestene](https://discourse.paraview.org/u/pkestene)
#### Post date: [June 14, 2024, 6:36pm UTC](https://discourse.paraview.org/t/cmake-error-when-building-a-paraview-plugin-external-library-linking/14849/3 "2024-06-14T18:36:14Z")
Ok, I see now. Thanks.
---
### Author:  [@pkestene](https://discourse.paraview.org/u/pkestene)
#### Post date: [June 17, 2024, 6:12pm UTC](https://discourse.paraview.org/t/cmake-error-when-building-a-paraview-plugin-external-library-linking/14849/4 "2024-06-17T18:12:48Z")
I’ve renamed the module, I’ve also modified CMakeLists.txt that builds the module to use `vtk_module_find_package(PACKAGE Kokkos)` to detect external library. But still the error at generate step is still there and I don’t understand why.
Is there a way to debug the cmake generate step ?
---
### Author:  [@pkestene](https://discourse.paraview.org/u/pkestene)
#### Post date: [June 18, 2024, 7:16am UTC](https://discourse.paraview.org/t/cmake-error-when-building-a-paraview-plugin-external-library-linking/14849/5 "2024-06-18T07:16:37Z")
Hello,
Let me just take another example directly from Paraview sources, subfolder `Examples/Plugins/LagrangianIntegrationModel`
It builds fine.
Just for illustrating the problem, if I add those lines:
```auto
vtk_module_find_package(
PACKAGE Kokkos
)
vtk_module_link(LagrangianExample PRIVATE Kokkos::kokkos)
```
then the same cmake (from generator) comes again:
```auto
CMake Error in Plugin/CMakeLists.txt:
Evaluation file to be written multiple times with different content. This
is generally caused by the content evaluating the configuration type,
language, or location of object files:
/home/kestenerp/install/visualization/paraview/github/ParaView/Examples/Plugins/LagrangianIntegrationModel/_build/Plugin/CMakeFiles/LagrangianExample-client-server..args
CMake Error in Plugin/LagrangianExample/CMakeLists.txt:
Evaluation file to be written multiple times with different content. This
is generally caused by the content evaluating the configuration type,
language, or location of object files:
/home/kestenerp/install/visualization/paraview/github/ParaView/Examples/Plugins/LagrangianIntegrationModel/_build/Plugin/LagrangianExample/CMakeFiles/LagrangianExample-hierarchy..args
```
Again, despite the cmake error, the build is ok.
There is obviously something that I didn’t understand about linking a plugin module to an external library.
Can someone help ?
---
### Author:  [@ben.boeckel](https://discourse.paraview.org/u/ben.boeckel)
#### Post date: [June 19, 2024, 12:03pm UTC](https://discourse.paraview.org/t/cmake-error-when-building-a-paraview-plugin-external-library-linking/14849/6 "2024-06-19T12:03:36Z")
That is certainly weird… I notice the `..args` in the paths which seems like you have an empty string configuration value? Can you provide the target definition of `Kokkos::kokkos`?
---
### Author:  [@pkestene](https://discourse.paraview.org/u/pkestene)
#### Post date: [June 19, 2024, 3:59pm UTC](https://discourse.paraview.org/t/cmake-error-when-building-a-paraview-plugin-external-library-linking/14849/7 "2024-06-19T15:59:27Z")
About `..args` : the log above was generated without `CMAKE_BUILD_TYPE`; when add a build type, it doesn’t change the error message.
Regarding the definition of target `Kokkos::kokkos`, looking at KokkosTargets.cmake in install directory, one can see:
```auto
# Create imported target Kokkos::kokkos
add_library(Kokkos::kokkos INTERFACE IMPORTED)
set_target_properties(Kokkos::kokkos PROPERTIES
INTERFACE_INCLUDE_DIRECTORIES "${_IMPORT_PREFIX}/include"
INTERFACE_LINK_LIBRARIES "Kokkos::kokkoscore;Kokkos::kokkoscontainers;Kokkos::kokkosalgorithms;Kokkos::kokkossimd"
)
```
all the other `Kokkos::` targets are either SHARED or INTERFACE IMPORTED libraries.
I can provide the entire file if needed. Anything particular should be noticed ? One can also see that Kokkos is linking to libdl, could this be a problem (for whatever reason) ?
Is there a way to trace inside cmake to understand how the error is generated ?
---
### Author:  [@ben.boeckel](https://discourse.paraview.org/u/ben.boeckel)
#### Post date: [June 19, 2024, 6:04pm UTC](https://discourse.paraview.org/t/cmake-error-when-building-a-paraview-plugin-external-library-linking/14849/8 "2024-06-19T18:04:57Z")
Yes. Run `cmake --trace-expand` (and redirect stderr to a file). Searching for the problematic paths should find where they’re being called from.
---
### Author:  [@pkestene](https://discourse.paraview.org/u/pkestene)
#### Post date: [June 20, 2024, 9:26am UTC](https://discourse.paraview.org/t/cmake-error-when-building-a-paraview-plugin-external-library-linking/14849/9 "2024-06-20T09:26:48Z")
Hello,
I’ve recompiled cmake just to make the error message clearer (and print the difference when conflict happens).
I found the origin of the conflict when generating those files (e.g. `LagrangianExample-client-server..args`). They are generated for language C and CXX and Kokkos is adding symbol `KOKKOS_DEPENDENCE` for CXX for compile and link (that’s the difference):
```auto
set_target_properties(Kokkos::kokkoscore PROPERTIES
INTERFACE_COMPILE_DEFINITIONS "\$<\$:KOKKOS_DEPENDENCE>"
INTERFACE_COMPILE_FEATURES "cxx_std_17"
INTERFACE_COMPILE_OPTIONS "\$<\$:>"
INTERFACE_INCLUDE_DIRECTORIES "${_IMPORT_PREFIX}/include"
INTERFACE_LINK_LIBRARIES "Kokkos::HWLOC;Kokkos::LIBDL;OpenMP::OpenMP_CXX"
INTERFACE_LINK_OPTIONS "\$<\$:-DKOKKOS_DEPENDENCE>"
)
```
This symbol is used by kokkos; when compiling, kokkos actually uses `kokkos_launch_compiler` to redirect to the actual c++ compiler/linker when needed (e.g. when compiling for Nvidia/Cuda). I’m only using Kokkos::OpenMP backend, but this symbol is always defined for language CXX (and not for C).
I don’t quite understand why this problem only happens now, only when building a paraview plugin.
Is is really necessary to generate those files for C language ? Maybe, that is the root cause of the problem ?
Any suggestion on how to fix that ?
---
### Author:  [@ben.boeckel](https://discourse.paraview.org/u/ben.boeckel)
#### Post date: [June 21, 2024, 11:10am UTC](https://discourse.paraview.org/t/cmake-error-when-building-a-paraview-plugin-external-library-linking/14849/10 "2024-06-21T11:10:13Z")
> [@pkestene](#):
>
> I don’t quite understand why this problem only happens now, only when building a paraview plugin.
> Is is really necessary to generate those files for C language ? Maybe, that is the root cause of the problem ?
Seems to be the case. I’m not sure what makes it get generated per-language though… Is there only the one `file(GENERATE)` call that mentions this path as an `OUTPUT` or are there multiple instances in the `--trace-expand` log?
---
### Author:  [@pkestene](https://discourse.paraview.org/u/pkestene)
#### Post date: [June 21, 2024, 1:01pm UTC](https://discourse.paraview.org/t/cmake-error-when-building-a-paraview-plugin-external-library-linking/14849/11 "2024-06-21T13:01:14Z")
yes, there is only one call to `file(GENERATE)`
and I noticed that **every occurence** of `file(GENERATE)` leads to 2 calls to `cmGeneratorExpressionEvaluationFile::Generate`, one for C language, one for CXX language.
There error message above correspond to the two occurences where C and CXX generated file disagree.
In my case, the file that is actually used finaly is the one generated using lang=C, the second time, the error message is displayed. So I think there is something wrong, it means if the third party c++ library is defining compilation flags specific for CXX, they will be ignored when building the plugin.
The `file(GENERATE)` calls that are causing problem are the ones coming from paraview’s :
- vtkModule.cmake in function `_vtk_module_write_wrap_hierarchy`
- vtkModuleWrapClientServer.cmake in function `_vtk_module_wrap_client_server_sources`
Would it be a solution to modify the calls to `file(GENERATE)` at those locations by adding `CONDITION ` where condition would be true only for lang=CXX (since anyway the plugin is written in CXX) ?
---
### Author:  [@pkestene](https://discourse.paraview.org/u/pkestene)
#### Post date: [June 5, 2025, 9:29am UTC](https://discourse.paraview.org/t/cmake-error-when-building-a-paraview-plugin-external-library-linking/14849/12 "2025-06-05T09:29:45Z")
I’m still seeing this error at cmake generate stage when trying to build a Paraview plugin that links with a C++ library.
Despite the cmake error, the generated file are usable, I can build my plugin that is ok.
But still this error (as summarized just above in previous message) makes me think there is a problem because cmake is trying to generate multiple times the files (once for C, once for CXX) but I would expect to be generated only for CXX (as the plugin is a CXX cmake project)
---
### Author:  [@ben.boeckel](https://discourse.paraview.org/u/ben.boeckel)
#### Post date: [June 13, 2025, 10:13am UTC](https://discourse.paraview.org/t/cmake-error-when-building-a-paraview-plugin-external-library-linking/14849/13 "2025-06-13T10:13:54Z")
I agree there’s a problem here. Can you please [file an issue](https://gitlab.kitware.com/paraview/paraview/-/issues) so that it doesn’t get lost?
---
### Author:  [@pkestene](https://discourse.paraview.org/u/pkestene)
#### Post date: [June 17, 2025, 11:29am UTC](https://discourse.paraview.org/t/cmake-error-when-building-a-paraview-plugin-external-library-linking/14849/14 "2025-06-17T11:29:04Z")
Ok, thanks. I’ll do that shortly and provide a minimalist reproducer if it can help analysis.