How to consume exported static library

Code
1

I’ve worked thru packaging a static library using the TGZ generator. If I were to host this file somewhere. How would I consume it in another project. I know FetchContent can handle remote archives, but they need to contain a CMakeLists.txt.

2

If I understand the situation correctly, isn’t it just a matter of using find_package to locate the library once it’s installed locally?

3

I only want to use it in the local project. I do not want to affect the global system state. Ideally I wouldn’t have to do any extra steps before calling CMake and it would work like FetchContent.

4

This exported cmake config package is not right!

See Is beman.exemplar/beman.exemplar-version.cmake a vallid package name? - #2 by ClausKlein

5

what?

6

If you install it, cmake will not find it.

7

Let me reframe the question. Given a URL to a tarball created with CPack with the TGZ generator. How would I use it in a CMake project? Is there any way to directly reference the URL in the CMakeLists.txt? If not, how can I reference it after downloading it and extracting it?

8

With this cmake file names in the tar file, you can’t use it!

9

I’ve removed the example from my question. I’m looking for help figuring out the workflow for consuming packaged CMake projects.

10

you may use find_package() after installing your package.

11

Can you explain what “installing” means in this context?

12

extracting the tar file to the right place.

or cmake --install ...

13

Assuming that you have a config file suitable for find_package, you can download the tgz, unpack it, add the path to CMAKE_ MODULE_PATH and call find_ package.

Without the config file, you can create the imported library target in your own.

14

By downloading it with file(DOWNLOAD …):

set(SOME_FILE "some.tgz")
message(STATUS "Downloading the file...")
file(DOWNLOAD "https://your.domain/data/${SOME_FILE}"
    "${CMAKE_CURRENT_SOURCE_DIR}/external/${SOME_FILE}"
    #SHOW_PROGRESS
    EXPECTED_HASH SHA1=b28c4cdfd737c41d1252945224aaddf97e45dc27 # should be the actual hash
    STATUS DOWNLOAD_DATASETS_RESULTS
)
list(GET DOWNLOAD_DATASETS_RESULTS 0 DOWNLOAD_STATUS_CODE)
list(GET DOWNLOAD_DATASETS_RESULTS 1 DOWNLOAD_ERROR_MESSAGE)
if(${DOWNLOAD_STATUS_CODE} EQUAL 0)
    message(STATUS "...successfully downloaded the file")
else()
    file(REMOVE "${CMAKE_CURRENT_SOURCE_DIR}/external/${SOME_FILE}")
    message(WARNING "...failed to download the file. ${DOWNLOAD_ERROR_MESSAGE}") # might want to use FATAL_ERROR instead of WARNING
endif()

But since it’s a .tgz archive, you’ll also need to unpack it, perhaps with a cmake -E. And then, as many have already mentioned, ideally you’d need to have a CMake config for your package (which is auto-generated if you have a proper installation procedure), otherwise you’d need to manually add its headers and binaries to your project.

I’d recommend you to use a package manager (such as vcpkg) for all this. Higher entry level, for sure, but then such tasks will get much more simpler for you going forward.

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