# Experimenting with FetchContent - issue with Jansson
**URL:** https://discourse.cmake.org/t/experimenting-with-fetchcontent-issue-with-jansson/9079
**Category:** Code
**Tags:** gen:xcode
**Created:** [September 25, 2023, 7:41am UTC](https://discourse.cmake.org/t/experimenting-with-fetchcontent-issue-with-jansson/9079 "2023-09-25T07:41:08Z")
**Posts on this page:** 7
**Page:** 1
### Author:  [@Andrew](https://discourse.cmake.org/u/Andrew)
#### Post date: [September 25, 2023, 7:41am UTC](https://discourse.cmake.org/t/experimenting-with-fetchcontent-issue-with-jansson/9079/1 "2023-09-25T07:41:08Z")
Starting to wrap my head around FetchContent, so tried some demo code using Jansson library.
App CMakeLists.txt:
```auto
cmake_minimum_required( VERSION 3.24 )
project( FetchContentTest
VERSION 0.1
DESCRIPTION "Test use of FetchContent"
LANGUAGES C
)
include( cmake/FetchRules.cmake )
FetchContent_MakeAvailable(
jansson
)
add_executable( json_test )
target_sources( json_test PRIVATE
src/main.c
)
target_link_libraries( json_test PRIVATE jansson )
```
The ‘cmake/FetchRules.cmake’ include:
```auto
include( FetchContent )
FetchContent_Declare(
jansson
GIT_REPOSITORY https://github.com/akheron/jansson.git
GIT_TAG 684e18c927e89615c2d501737e90018f4930d6c5 # v2.14
)
```
Then I run `cmake -S source -B Build/my_build_dir -G Xcode`
CMake process completes successfully, but when I try to compile I get an error that `#include "jansson.h"` - not found. “” or \<\> makes no difference. I can see the Jansson library has been downloaded and built in `_deps`, but I’m not getting a -I path to it in the Xcode build.
Jansson doesn’t use an alias, so I can’t tell whether CMake is not finding the target (and thus assuming its linking to an existing binary library) or something else is broken.
Any guidance?
---
### Author:  [@ben.boeckel](https://discourse.cmake.org/u/ben.boeckel)
#### Post date: [September 25, 2023, 3:43pm UTC](https://discourse.cmake.org/t/experimenting-with-fetchcontent-issue-with-jansson/9079/2 "2023-09-25T15:43:30Z")
@craig.scott?
---
### Author:  [@ClausKlein](https://discourse.cmake.org/u/ClausKlein)
#### Post date: [September 25, 2023, 7:54pm UTC](https://discourse.cmake.org/t/experimenting-with-fetchcontent-issue-with-jansson/9079/3 "2023-09-25T19:54:18Z")
> [@Andrew](#):
>
> `https://github.com/akheron/jansson.git`
Use jansson::jansson (with NAMESPACE)
---
### Author:  [@craig.scott](https://discourse.cmake.org/u/craig.scott)
#### Post date: [September 25, 2023, 9:48pm UTC](https://discourse.cmake.org/t/experimenting-with-fetchcontent-issue-with-jansson/9079/4 "2023-09-25T21:48:31Z")
The jansson project doesn’t follow good CMake practice. It uses `include_directories()` instead of `target_include_directories()` to add its header search paths. As a result, it doesn’t propagate the necessary header search paths to anything that links to the `jansson` target. You will have to add those yourself, or better would be to patch the upstream jansson project to use `target_include_directories()` instead.
---
### Author:  [@Andrew](https://discourse.cmake.org/u/Andrew)
#### Post date: [September 26, 2023, 12:48am UTC](https://discourse.cmake.org/t/experimenting-with-fetchcontent-issue-with-jansson/9079/5 "2023-09-26T00:48:54Z")
Ah, that makes sense. Thank you.
---
### Author:  [@Andrew](https://discourse.cmake.org/u/Andrew)
#### Post date: [September 26, 2023, 1:49am UTC](https://discourse.cmake.org/t/experimenting-with-fetchcontent-issue-with-jansson/9079/6 "2023-09-26T01:49:29Z")
Exploring a bit further (and apologies for implicit request to debug a third party library by proxy):
In the \_deps folder are three folders:
- jansson-src
- jansson-subbuild
- jansson-build
I assume `jansson-build` is the interesting one as far as output is concerned. When I switch to the `jansson` target in Xcode and “build”, this is the directory that gets a libjansson.a created.
`jansson-build/janssonConfig.cmake` and `jansson-build/cmake/janssonConfig.cmake` both refer to `${CMAKE_CURRENT_LIST_DIR}/janssonTargets.cmake`. The only `janssonTargets.cmake` I can find is in `jansson-build/CMakeFiles/Export/9b80b8ed102b5ab69af1c2960c090ea5/janssonTargets.cmake`.
This file (assuming it is executed) contains the following lines:
```auto
# Create imported target jansson::jansson
add_library(jansson::jansson STATIC IMPORTED)
set_target_properties(jansson::jansson PROPERTIES
INTERFACE_INCLUDE_DIRECTORIES "${_IMPORT_PREFIX}/include"
)
```
I assumed this would define `jansson::jansson` and add the appropriate per-target library paths. But when I change the dependency line to `target_link_libraries( json_test PRIVATE jansson::jansson )` then CMake complains that `jansson::jansson` is not found.
I picked the Jansson library to begin experimenting with because I wanted the functionality, not because it was the cleanest CMake example. That may have been a mistake. I think I’ll fork it and try hacking on the CMake files to see what happens.
---
### Author:  [@Andrew](https://discourse.cmake.org/u/Andrew)
#### Post date: [September 26, 2023, 4:30am UTC](https://discourse.cmake.org/t/experimenting-with-fetchcontent-issue-with-jansson/9079/7 "2023-09-26T04:30:19Z")
Made some mods - moving `add_definitions` to `target_compile_definitions` and `include_directories` to `target_include_directories` with distinct build and install rules. Seems to work now.