# Findmodule transitivity?
**URL:** https://discourse.cmake.org/t/findmodule-transitivity/4333
**Category:** Usage
**Created:** [October 25, 2021, 8:30am UTC](https://discourse.cmake.org/t/findmodule-transitivity/4333 "2021-10-25T08:30:41Z")
**Posts on this page:** 6
**Page:** 1
### Author:  [@adaldev](https://discourse.cmake.org/u/adaldev)
#### Post date: [October 25, 2021, 8:30am UTC](https://discourse.cmake.org/t/findmodule-transitivity/4333/1 "2021-10-25T08:30:41Z")
Hi,
I have a library project A that depend on a third-party library B that is not properly packaged (I can’t use find\_package directly on it).
Thus I wrote a FindB.cmake file whose path I give to A, using the variable CMAKE\_MODULE\_PATH.
I now have a different project C (an application) that make use of A.
find\_package(A) succeed but I’ve got the following error:
CMake Error at …/cmake-3.19/Modules/CMakeFindDependencyMacro.cmake:47 (find\_package):
By not providing “FindB.cmake” in CMAKE\_MODULE\_PATH this project
has asked CMake to find a package configuration file provided by
“B”, but CMake did not find one.
Could not find a package configuration file provided by “B” with
any of the following names:
```
BConfig.cmake
b-config.cmake
```
…
Does it mean that B locations were not properly propagate through the package A? Do I need to explicitly give FindB.cmake to C? Or do I do something wrong? In which case, what is the proper way to propagate a dependency “wrapped” with a FindModule file?
Regards,
A.
---
### Author:  [@ClausKlein](https://discourse.cmake.org/u/ClausKlein)
#### Post date: [October 26, 2021, 7:18pm UTC](https://discourse.cmake.org/t/findmodule-transitivity/4333/2 "2021-10-26T19:18:09Z")
perhaps this blog may help you: [https://crascit.com/2015/02/02/cmake-target-dependencies/](https://crascit.com/2015/02/02/cmake-target-dependencies/)
---
### Author:  [@adaldev](https://discourse.cmake.org/u/adaldev)
#### Post date: [October 28, 2021, 3:09pm UTC](https://discourse.cmake.org/t/findmodule-transitivity/4333/3 "2021-10-28T15:09:16Z")
Hi,
Thanks for the link but it puzzles me in two ways:
1- I think I already understood an applied the concepts in this blog
2- I don’t understand the specific boost example
indeed, even if foo does not use Boost binaries, it is declared anyway as a dependency that will be propagated to gumby
bar uses boost headers internally but it is not said that it uses it in its interface so why target\_include\_directories(bar PUBLIC ${Boost\_INCLUDE\_DIRS})
instead of
target\_include\_directories(private PUBLIC ${Boost\_INCLUDE\_DIRS})
gumby uses parts of bar in its interface but not internally
why not
target\_link\_libraries(gumby PRIVATE foo INTERFACE bar) ?
Anyway, it does not speak about my FindModule issue: When I “find\_package” a target A that depends at least privately on another one B that can be found by a FindModule.cmake, clients of my target need to link against B transitively but the link fails as B is not found (dependencies info within package A does not seem to describe the target B but only declare a dependency)
it seems that, if C depends on A that depends on B, when in C Cmakelist I do find\_package(A), cmake does not import B but calls find\_package(B) which fails as from C CMakeList, FindB.cmake is unknown
Am I wrong ?
Otherwise, is there a good practice with respect to FindModule.cmake location and CMake\_Module\_Path setting?
Thanks,
A.
---
### Author:  [@ClausKlein](https://discourse.cmake.org/u/ClausKlein)
#### Post date: [October 29, 2021, 10:00am UTC](https://discourse.cmake.org/t/findmodule-transitivity/4333/4 "2021-10-29T10:00:45Z")
Hi,
in general [find\_package(… CONFIG …)](https://cmake.org/cmake/help/v3.22/command/find_package.html#search-procedure) should be used to find exported `cmake config packages`.
Each packages should export its `compile options`, `include directories`, and sure its `direct link dependencies`.
If everything is **PUBLIC** or **INTERFACE** exported, it works fine. But, every packages must be properly installed!
A more academic example is this: [minijson\_reader/CMakeLists.txt at feature/use-string-buffer · ClausKlein/minijson\_reader · GitHub](https://github.com/ClausKlein/minijson_reader/blob/feature/use-string-buffer/CMakeLists.txt) which use [CPM.cmake](https://github.com/cpm-cmake/CPM.cmake) to make the fetching of dependencies much easier.
The general behaviour is documented in the [CMake using-dependencies-guide](https://cmake.org/cmake/help/v3.22/guide/using-dependencies/index.html)
and [importing-exporting-guid](https://cmake.org/cmake/help/latest/guide/importing-exporting/index.html)
I hope this helps you
Claus
---
### Author:  [@ClausKlein](https://discourse.cmake.org/u/ClausKlein)
#### Post date: [October 31, 2021, 5:50pm UTC](https://discourse.cmake.org/t/findmodule-transitivity/4333/5 "2021-10-31T17:50:56Z")
> [@adaldev](#):
>
> In which case, what is the proper way to propagate a dependency “wrapped” with a FindModule file?
You should use `find_package(... CONFIG ...)` variant and your TPL packages should be fixed to export the `CMake config package` right with their own dependencies!
---
### Author:  [@adaldev](https://discourse.cmake.org/u/adaldev)
#### Post date: [November 2, 2021, 10:42am UTC](https://discourse.cmake.org/t/findmodule-transitivity/4333/6 "2021-11-02T10:42:07Z")
Thanks for your feedback.
My issue with inherited dependency through a FindModule.cmake is not solved by I have a few tracks to follow.
Regards
A.