# How to install an external project?

**URL:** https://discourse.cmake.org/t/how-to-install-an-external-project/888
**Category:** Code
**Tags:** os:windows
**Created:** [March 30, 2020, 7:18pm UTC](https://discourse.cmake.org/t/how-to-install-an-external-project/888 "2020-03-30T19:18:10Z")
**Posts on this page:** 1
**Showing post:** 11

<div class="post-metadata">

### Author: ![ajm](https://discourse.cmake.org/user_avatar/discourse.cmake.org/ajm/32/443_2.png) [@ajm](https://discourse.cmake.org/u/ajm)
#### Post date: [April 1, 2020, 8:20pm UTC](https://discourse.cmake.org/t/how-to-install-an-external-project/888/11 "2020-04-01T20:20:54Z")

</div>

Hi Florian,

Thanks! The `CPACK_INSTALL_CMAKE_PROJECTS` was the thing that I was missing, this was quite a journey!

I did some experimentation and it seems like that’s about all I needed actually; I was able to remove all of the target imports and exports and the packaging still worked.

Here’s what my files looked like:

# Root / Superbuild CMakeLists.txt

```auto
cmake_minimum_required (VERSION 2.6)

project(SUPERBUILD_ROOT)

include(ExternalProject)

# ----------------------------------------------------------------------------------------------------------------------
# Set up our external projects
# ----------------------------------------------------------------------------------------------------------------------

ExternalProject_Add(extern
                    GIT_REPOSITORY "[extern's git repository]"
                    CMAKE_ARGS
                        -DCMAKE_INSTALL_PREFIX:PATH=${CMAKE_CURRENT_BINARY_DIR}/extern-install
)

ExternalProject_Add(Main
                    GIT_REPOSITORY "[main's git repository]"
                    CMAKE_ARGS
                        -DCMAKE_INSTALL_PREFIX:PATH=${CMAKE_CURRENT_BINARY_DIR}/Main-install
                    DEPENDS 
                        extern
)

# ----------------------------------------------------------------------------------------------------------------------
# Read the "binary directories" of both external projects
#
# CMake calls the build\extern-prefix\src\extern-build a "Binary directory", but it's really the directory where the VS Solution is, etc.
# I'd call these "build directories", to be honest...
# ----------------------------------------------------------------------------------------------------------------------

unset(BINARY_DIR)

#This function writes to a variable named BUILD_DIR... okay sure?
#It'll get clobbered twice so we have to save the result somewhere else.....
ExternalProject_Get_property(extern BINARY_DIR) 
set(externBuildDirectory ${BINARY_DIR})
message("extern's build directory is " ${externBuildDirectory})

unset(BINARY_DIR)

ExternalProject_Get_property(Main BINARY_DIR)
set(mainBuildDirectory ${BINARY_DIR})
message("Main's build directory is " ${mainBuildDirectory})

unset(BINARY_DIR)

# ----------------------------------------------------------------------------------------------------------------------
# Write these paths to CPACK_INSTALL_CMAKE_PROJECTS so that CPack will know to visit these projects for packaging
# ----------------------------------------------------------------------------------------------------------------------

# https://cmake.org/cmake/help/latest/module/CPack.html?highlight=cpack_install_cmake_projects#variable:CPACK_INSTALL_CMAKE_PROJECTS
# project build dir proj name build all components "Directory" (??)
set(externProjectInfo ${externBuildDirectory} "extern" "ALL" "/")
set(mainProjectInfo ${mainBuildDirectory} "Main" "ALL" "/")

# both of these go in one list
set(allProjectInfo ${mainProjectInfo} ${externProjectInfo})

message("CPACK_INSTALL_CMAKE_PROJECTS before append is " ${CPACK_INSTALL_CMAKE_PROJECTS})

# I think this variable has to be set before CPack is included.
set(CPACK_INSTALL_CMAKE_PROJECTS ${allProjectInfo})

message("CPACK_INSTALL_CMAKE_PROJECTS after append is " ${CPACK_INSTALL_CMAKE_PROJECTS})

# ----------------------------------------------------------------------------------------------------------------------
# Now include CPack (must be last)
# ----------------------------------------------------------------------------------------------------------------------

include(CPack)
set(CPACK_GENERATOR NSIS)

```

# Extern (AKA Dep)'s CMakeLists.txt

```auto
cmake_minimum_required (VERSION 2.6)

project(SUPERBUILD_EXTERN)

message("Hello from the external repository's CMakeLists.txt!")

# Creates the executable with the listed sources and adds sources to the Solution Explorer
# (but you won't see extern.c in the root (superbuild) solution)
add_executable (extern_binary extern.c)

install (TARGETS extern_binary 
        RUNTIME DESTINATION "DirectoryForCmakeSuperbuild_Extern"
        )

```

# Main’s CMakeLists.txt

```auto
cmake_minimum_required (VERSION 2.6)

project(SUPERBUILD_MAIN)

message("Hello from the main repository's CMakeLists.txt!")

# Creates the executable with the listed sources and adds sources to the Solution Explorer
# (but you won't see main.c in the root (superbuild) solution)
add_executable (main_binary main.c)

install (TARGETS main_binary 
         RUNTIME DESTINATION "DirectoryForCmakeSuperbuild_Main")

```

I suppose I’ll also put my github repositories here too, in case it helps anyone else:

- [Root (AKA Superbuild)](https://github.com/amelvill-umich/CMake_Superbuild_Root)
- [Main](https://github.com/amelvill-umich/CMake_Superbuild_Main)
- [Extern (AKA Dep)](https://github.com/amelvill-umich/CMake_Superbuild_Extern)

# One thing I’m wondering about though,

If it’s not possible to `install` using imported projects, what is the purpose of importing targets? Is it just for programs that don’t need to be packaged?

---

_[View the full topic](https://discourse.cmake.org/t/how-to-install-an-external-project/888)._