[CMake] How to link against projects added through FetchContent

[Saad Khattak]

Hi,

I would like to know how to use the FetchContent properly so that I can
link against downloaded (CMake enabled) projects. I have looked at the
CMake docs, which although are quite thorough, almost always fail to list a
complete example which is incredibly crucial to get up and running quickly.

With ExternalProject_Add, we use add_dependencies(...) but that doesn't
seem to be the case for FetchContent. Since I can immediately call
add_subdirectory(...), I assumed that I can simply link to the library. But
that doesn't seem to do anything.

Here's my CMakeLists.txt
``````````````````````````````````````````````````````````````
cmake_minimum_required(VERSION 3.5)
project(testProj)

include(FetchContent)

FetchContent_Declare(
  Catch2
  GIT_REPOSITORY "https://github.com/catchorg/Catch2"
  TEST_COMMAND ""
  )

FetchContent_GetProperties(catch)
if(NOT Catch2_POPULATED)
  FetchContent_Populate(Catch2)
  add_subdirectory(${Catch2_SOURCE_DIR} ${Catch2_BINARY_DIR})
endif()

add_executable(testExe main.cpp)

target_link_libraries(testExe Catch2)
``````````````````````````````````````````````````````````````

CMake populates Catch2 with Catch2-NOTFOUND.

So, my question is, how do I link against projects added through
FetchContent?

- Saad
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