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I try to add all dependencies needed for my project to compile over CMake. This should reduce the overhead others will have when they want to compile the project for the first time.

To achive this, I tried to use FetchContent. So far so good, when I link the generated targets its not a problem at all. But now I have a library depending itself on annother lib which isn't included as submodule. The lib tries to find the dependency over find_package. How can I get find_package to find the library?

What I tried so far:

  • adding an alias target and defined all variables set by find_package
  • Setting the LIB_DIR to the build directory and called find_package

Here a minimal snipped of my CMake code of the later:

cmake_minimum_required(VERSION 3.14)

find_package(ZLIB)
if (NOT ZLIB_FOUND)
    FetchContent_Declare(zlib_fetch
        GIT_REPOSITORY https://github.com/madler/zlib.git
        GIT_TAG cacf7f1d4e3d44d871b605da3b647f07d718623f
        )
    FetchContent_MakeAvailable(zlib_fetch)
    set(ZLIB_DIR ${zlib_fetch_BINARY_DIR})
    message(${zlib_fetch_BINARY_DIR})
#simulates the call in the other library:
    find_package(ZLIB REQUIRED) 
endif (NOT ZLIB_FOUND)
Fabian Keßler
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1 Answers1

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Starting with CMake 3.24, FetchContent_Declare has OVERRIDE_FIND_PACKAGE option which, when specified, makes CMake redirect the subsequent calls to find_package(<name>) so that FetchContent_Declare(<name> ...) satisfies the dependency (note that <name> must stay the same here).

Eyjafl
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  • What if my project can use the version 3.14? How can I find a package after a FetchContent_Declare? – ywiyogo Aug 26 '22 at 13:32
  • I think in that case you'd have to create your own function based off of [the 3.24 version of `FetchContent_Declare`](https://github.com/Kitware/CMake/blob/164a156c7c26aaf4f30e73ae0cdb6d2e8a10e0a4/Modules/FetchContent.cmake#L1204) – Dash2TheDot Oct 14 '22 at 15:28