[CMake] Using find_package fails to find related subprojects that are exported to the package registry

[Rafael Vargas]

I have a similarly organized project and it works without any of the
find_package
and the export commands.

If you do include all of the CMakeFiles.txt files using add_directory, then
it should be enough to:

In my_common_libs/common_lib1/CMakeLists.txt:
    add_library(common_lib1 ...)

In executable1/CMakeLists.text:
    add_executable(executable1 ...)
    target_link_libraries(executable1 common_lib1 )

This way you don't need to worry about ordering your add_directory commands
as all the link dependencies will be ordered by CMake.

-- 
Rafael Vargas


Em qua, 10 de abr de 2019 às 18:08, Timothy Wrona <tjwrona1992 at gmail.com>
escreveu:

> Hi fellow CMake programmers! I've got a bit of a tricky situation and I
> wonder if anyone has ever dealt with this before.
>
> I am trying to configure a project that has a structure as follows
>
> myproject/
>     executable1/  <-- depends on common_lib1
>     my_common_libs/
>         common_lib1/
>         common_lib2/
>
> Note: Before I begin - this is a legacy system and is MUCH larger than
> what I am showing here so restructuring the whole project is not really an
> option. Let me begin by describing the CMakeLists.txt structure.
>
> In myproject/CMakeLists.txt subdirectories are added as follows:
>
> file(GLOB entries *)
> foreach(entry ${entries})
>   if (IS_DIRECTORY ${entry} AND EXISTS ${entry}/CMakeLists.txt)
>     add_subdirectory(${entry})
>   endif()
> endforeach()
>
> my_common_libs/CMakeLists.txt does the same...
>
> Then my_common_libs/common_lib1/CMakeLists.txt does what is necessary to
> define the library and export the target to the local package registry:
>
> add_library(common_lib1 ...)
>
> export(TARGETS common_lib1 NAMESPACE common_lib1:: FILE
> common_lib1-targets.cmake)
> file(COPY common_lib1-config.cmake DESTINATION ${CMAKE_CURRENT_BINARY_DIR})
> export(PACKAGE common_lib1)
>
> my_common_libs/common_lib2/CMakeLists.txt does the same and both have
> "common_libx-config.cmake" files that properly load the corresponding
> "-targets.cmake" files.
>
> In executable1/CMakeLists.text I do what is necessary to find the package
> and use it:
>
> add_executable(executable1 ...)
>
> find_package(common_lib1 REQUIRED) <-- this is where I am having the
> problem
> target_link_libraries(executable1
>     common_lib1::common_lib1
> )
>
> Now this is where things get hairy...
>
> If I go into common_lib1 and manually build that first, it puts it in the
> package registry and then I can go to "executable1" and build that and it
> finds the package, and builds, and links fine.
> BUT... if I clean the project and then try to build it from the top level
> it immediately fails and says it can't locate the package "common_lib1".
>
> I understand I could probably replace the GLOB commands with explicit
> "add_subdirectory" calls and then carefully reorder all of the
> "add_subdirectory" commands to add things in dependency order, but that
> would be really tedious with how large the project is and is really not the
> way the whole rest of the system is done... It feels somewhat brittle
> because then I am essentially declaring the dependencies from outside of
> the modules themselves.
>
> Is there any way to force CMake to do all of the "export" commands up
> front to essentially initialize the package registry so it will be aware of
> common_lib1 when I compile from the "myproject" level? Or is there another
> solution I haven't even considered that could solve this same problem?
>
> Thanks,
> Tim
> --
>
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