[CMake] how to debug CPack creation

[Eric Noulard]

>
>
> And the content is:
> $ rpm -qpl softether-vpnserver-5.1.9660-1.x86_64.rpm
> /lib
> /lib/systemd
> /lib/systemd/system
> /lib/systemd/system/softether-vpnserver.service
> /usr/libexec
> /usr/libexec/softether
> /usr/libexec/softether/vpnserver
> /usr/libexec/softether/vpnserver/hamcore.se2
> /usr/libexec/softether/vpnserver/vpnserver
> /usr/local
> /usr/local/bin
> /usr/local/bin/vpnserver
>
> the content of the .deb is similar:
> $ dpkg-deb -c softether-vpnserver_5.1.9660_amd64.deb
> drwxr-xr-x root/root         0 2018-10-20 14:45 ./lib/
> drwxr-xr-x root/root         0 2018-10-20 14:45 ./lib/systemd/
> drwxr-xr-x root/root         0 2018-10-20 14:45 ./lib/systemd/system/
> -rw-r--r-- root/root       700 2018-10-20 14:45
> ./lib/systemd/system/softether-vpnserver.service
> drwxr-xr-x root/root         0 2018-10-20 14:45 ./usr/
> drwxr-xr-x root/root         0 2018-10-20 14:45 ./usr/libexec/
> drwxr-xr-x root/root         0 2018-10-20 14:45 ./usr/libexec/softether/
> drwxr-xr-x root/root         0 2018-10-20 14:45
> ./usr/libexec/softether/vpnserver/
> -rw-r--r-- root/root   1770716 2018-10-20 14:45
> ./usr/libexec/softether/vpnserver/hamcore.se2
> -rwxr-xr-x root/root   2088960 2018-10-20 14:45
> ./usr/libexec/softether/vpnserver/vpnserver
> drwxr-xr-x root/root         0 2018-10-20 14:45 ./usr/local/
> drwxr-xr-x root/root         0 2018-10-20 14:45 ./usr/local/bin/
> -rwxr-xr-x root/root        72 2018-10-20 14:45 ./usr/local/bin/vpnserver
>
> The main question is, what filesystem layout do you expect for those files?
>
>
Now I think I get it.
IN vpnserver CMakeLists.txt you do:

install_systemd_service("vpnserver"
"${CMAKE_SOURCE_DIR}/systemd/softether-vpnserver.service"
"${CMAKE_INSTALL_FULL_LIBEXECDIR}/softether/vpnserver/vpnserver")

So at this point (during CMake config step)
"${CMAKE_INSTALL_FULL_LIBEXECDIR}/softether/vpnserver/vpnserver"
is /usr/local/softether/vpnserver/vpnserver

In your install_systemd_service CMake macro wrapper you do:

macro(install_systemd_service component file_path binary_path)
    get_filename_component(file_name ${file_path} NAME)
    get_filename_component(binary_directory ${binary_path} DIRECTORY)

    file(READ ${file_path} FILE_CONTENT)
    string(REPLACE "[DIRECTORY]" ${binary_directory} FILE_CONTENT
${FILE_CONTENT})
    string(REPLACE "[BINARY]" ${binary_path} FILE_CONTENT ${FILE_CONTENT})
    file(WRITE ${CMAKE_SOURCE_DIR}/tmp/systemd/${file_name} ${FILE_CONTENT})
...

So you generate a systemd service file which contains /usr/local prefix
because this is the one which
is know during "CMake configuration step".

You cannot do that this way with .deb or .rpm because you don't know the
"actual" prefix that will be in the package
because it is controlby CPACK_PACKAGING_INSTALL_PREFIX  "at CPack time",
i.e. when CPack runs.

It's even worse because .deb or .rpm may be relocated see e.g.:
https://www.cyberciti.biz/faq/howto-install-rpm-package-into-another-directory/

When you want to install script that should know where things get installed
you have 3 options:

1) Assume the binary executable is installed in the path
    thus call the executable as-is "vpnserver" without absolute path

2) Put a pre- or post- install script that will compute the appropriate
path
   **during package installation** when you are sure what the real path
will be.
   Have a look at CPACK_DEBIAN_PACKAGE_CONTROL_EXTRA in
https://cmake.org/cmake/help/latest/cpack_gen/deb.html
or
https://cmake.org/cmake/help/latest/cpack_gen/rpm.html#variable:CPACK_RPM_SPEC_MORE_DEFINE

3) Ensure that you generate package with
   CMAKE_INSTALL_PREFIX == CPACK_PACKAGING_INSTALL_PREFIX
   This is ok but will break if the installation of the package is
relocated.

1) may be ok.
2) need a little work but is the more robust
3) may be enough but prevent relocatable install

-- 
Eric
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