make install fails: $CMAKE_INSTALL_DATAROOTDIR is empty because GNUInstallDirs is not included

[NeoChen1024]

Description

Running cmake .. -DCMAKE_INSTALL_PREFIX=$HOME/.local && make && make install fails with the following error:

CMake Error at app/qtapp/rtkconv_qt/cmake_install.cmake:74 (file):
  file cannot create directory: /applications.  Maybe need administrative
  privileges.
Call Stack (most recent call first):
  app/qtapp/cmake_install.cmake:47 (include)
  cmake_install.cmake:62 (include)

Root Cause

The top-level CMakeLists.txt does not include GNUInstallDirs. This means CMAKE_INSTALL_DATAROOTDIR is never defined and remains empty.

In app/qtapp/CMakeLists.txt, lines 4–5:

set(XDG_APPS_INSTALL_DIR "${CMAKE_INSTALL_DATAROOTDIR}/applications")
set(XDG_APPS_PIXMAPS_DIR "${CMAKE_INSTALL_DATAROOTDIR}/icons/")

With CMAKE_INSTALL_DATAROOTDIR empty, these evaluate to absolute paths /applications and /icons/ at the filesystem root. The install() rules in all 8 Qt app subdirectories (rtkconv_qt, rtkget_qt, rtklaunch_qt, rtknavi_qt, rtkplot_qt, rtkpost_qt, srctblbrows_qt, strsvr_qt) then attempt to write .desktop and icon files to these root paths, which requires root privileges.

Proposed Fix

Add include(GNUInstallDirs) to the top-level CMakeLists.txt right after project(). This standard CMake module defines CMAKE_INSTALL_DATAROOTDIR as share, so the paths correctly become share/applications and share/icons/.

Before:

project(rtklib LANGUAGES C CXX VERSION 2.4.3)

include(CTest)

After:

project(rtklib LANGUAGES C CXX VERSION 2.4.3)

include(GNUInstallDirs)
include(CTest)

Affected Files

• CMakeLists.txt (add include(GNUInstallDirs))
• app/qtapp/CMakeLists.txt (no change needed — variables will resolve correctly once GNUInstallDirs is included)

Environment

• OS: Any Linux
• CMake: 4.3
• Branch: master (commit a9df4ff)