### Author:  [@ingolf](https://discourse.cmake.org/u/ingolf)
#### Post date: [November 16, 2021, 5:39pm UTC](https://discourse.cmake.org/t/include-directories-target-property-not-reporting-indirect-ones/4493/1 "2021-11-16T17:39:58Z")
Hi,
in my project, there is
```auto
add_library(foo source1.c)
target_include_directories(foo PUBLIC foo_library_includes)
add library(bar source2.c)
target_link_libraries(bar PRIVATE foo)
```
Whenever I actually _compile_ `bar`, `foo_library_includes` is correctly added to the include path.
However, I’d like to use a function like the following
```auto
function(add_special_target library)
get_target_property(dirs ${library} INCLUDE_DIRECTORIES)
transmogrify(dirs) # macro prepends some prefix to each element in dirs
add_custom_target(${library}.special
COMMAND "special_processor ${dirs} further_arguments"
)
endfunction()
```
In fact, the custom command does a bit more, but I hope you get the intention.
Unfortunately, when using `add_special_target(bar)` after all the above definitions, the `get_target_property()` will not deliver the `foo_library_includes` although they are made applicable when _building_ the `bar` target.
What is the correct way to solve the problem? (CMake 3.21.3 here)
I acknowledge that similar questions have been posted before (like [this](https://discourse.cmake.org/t/interface-include-directories-not-transitive-for-target-link-libraries/4028) or [this one](https://discourse.cmake.org/t/transitive-dependencies-for-include-directories-break/4035)). However I do not yet see how generator expressions would help me here: `set (dirs $)` instead of `get_target_property()` won’t work, right?
Kind regards
Ingolf
---
### Author:  [@ben.boeckel](https://discourse.cmake.org/u/ben.boeckel)
#### Post date: [November 16, 2021, 8:33pm UTC](https://discourse.cmake.org/t/include-directories-target-property-not-reporting-indirect-ones/4493/2 "2021-11-16T20:33:18Z")
> [@ingolf](#):
>
> What is the correct way to solve the problem?
Use generator expressions. You can do something like this to put a prefix on each (in this case, `-I`, quotes, and newlines):
[https://gitlab.kitware.com/vtk/vtk/-/blob/dfb84f04bcd786b6198ee375c25055a4ec47b0ae/CMake/vtkModuleWrapPython.cmake#L168-172](https://gitlab.kitware.com/vtk/vtk/-/blob/dfb84f04bcd786b6198ee375c25055a4ec47b0ae/CMake/vtkModuleWrapPython.cmake#L168-172)
---
### Author:  [@JohannesWilde](https://discourse.cmake.org/u/JohannesWilde)
#### Post date: [November 17, 2021, 2:14pm UTC](https://discourse.cmake.org/t/include-directories-target-property-not-reporting-indirect-ones/4493/3 "2021-11-17T14:14:16Z")
Hi,
I stumbled upon exactly the same problem recently and was sadly unable to solve this till now.
I created a simple MWI [see [https://github.com/JohannesWilde/TestingCmake](https://github.com/JohannesWilde/TestingCmake) - as I am unable to upload a file here], where the configure output is as follows:
> lib1\_include: TestingCMake/dir1/include
> lib2\_include: TestingCMake/dir2/include
> lib1\_interface\_include: TestingCMake/dir1/include
> lib2\_interface\_include: TestingCMake/dir2/include
> lib1\_link: lib1\_link-NOTFOUND
> lib2\_link: lib1
> – Configuring done
> – Generating done
If I understand the CMake documentation for `INTERFACE_INCLUDE_DIRECTORIES` correctly [see [here](https://cmake.org/cmake/help/latest/prop_tgt/INTERFACE_INCLUDE_DIRECTORIES.html)]:
> When target dependencies are specified using `target\_link\_libraries(), CMake will read this property from all target dependencies to determine the build properties of the consumer.
, CMake does so somewhere at some point anyway. Is there a way to query those “build properties”? I.e. I want:
> lib2\_interface\_include: TestingCMake/dir2/include;TestingCMake/dir1/include
Thanks
Johannes
---
### Author:  [@ben.boeckel](https://discourse.cmake.org/u/ben.boeckel)
#### Post date: [November 17, 2021, 2:27pm UTC](https://discourse.cmake.org/t/include-directories-target-property-not-reporting-indirect-ones/4493/4 "2021-11-17T14:27:12Z")
> [@JohannesWilde](#):
>
> , CMake does so somewhere at some point anyway. Is there a way to query those “build properties”? I.e. I want:
Not at configure time. Only generator expressions can access that information (because it is only then when everything is known to answer such questions).
---
### Author:  [@JohannesWilde](https://discourse.cmake.org/u/JohannesWilde)
#### Post date: [November 17, 2021, 7:43pm UTC](https://discourse.cmake.org/t/include-directories-target-property-not-reporting-indirect-ones/4493/5 "2021-11-17T19:43:36Z")
Hi Ben,
thanks a lot. Great support. This clears it up for me.
Cheers
Johannes