CMake: rewrite FindSystemd.cmake file

Clarify that this is only needed for the sdjournal extcap interface and
report the found version in the CMake output.

Change-Id: I40bc540631bda32d0b92e4fcd59d8c1726606d86
Reviewed-on: https://code.wireshark.org/review/31834
Petri-Dish: Peter Wu <peter@lekensteyn.nl>
Tested-by: Petri Dish Buildbot
Reviewed-by: Peter Wu <peter@lekensteyn.nl>

3 files changed, 35 insertions, 37 deletions

diff --git a/CMakeLists.txt b/CMakeLists.txt
index a9482b3a97..7b222c8817 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1473,6 +1473,11 @@ set_package_properties(CARES PROPERTIES
 	URL "https://c-ares.haxx.se/"
 	PURPOSE "DNS name resolution for captures"
 )
+set_package_properties(Systemd PROPERTIES
+	URL "https://freedesktop.org/wiki/Software/systemd/"
+	DESCRIPTION "System and Service Manager (libraries)"
+	PURPOSE "Support for systemd journal extcap interface (sdjournal)"
+)
 
 string(TOUPPER "${CMAKE_BUILD_TYPE}" _build_type)
 message(STATUS "C-Flags: ${CMAKE_C_FLAGS} ${CMAKE_C_FLAGS_${_build_type}}")
diff --git a/cmake/modules/FindSystemd.cmake b/cmake/modules/FindSystemd.cmake
index 0ddf4f7ff4..6162d0d605 100644
--- a/cmake/modules/FindSystemd.cmake
+++ b/cmake/modules/FindSystemd.cmake
@@ -1,41 +1,37 @@
-# Copied from https://github.com/Cloudef/wlc/blob/master/CMake/FindSystemd.cmake
-#.rst:
-# FindSystemd
-# -------
 #
-# Find Systemd library
+# - Find systemd libraries
 #
-# Try to find Systemd library on UNIX systems. The following values are defined
-#
-# ::
-#
-#   SYSTEMD_FOUND         - True if Systemd is available
-#   SYSTEMD_INCLUDE_DIRS  - Include directories for Systemd
-#   SYSTEMD_LIBRARIES     - List of libraries for Systemd
-#   SYSTEMD_DEFINITIONS   - List of definitions for Systemd
-#
-#=============================================================================
-# Copyright (c) 2015 Jari Vetoniemi
-#
-# Distributed under the OSI-approved BSD License (the "License");
-#
-# This software is distributed WITHOUT ANY WARRANTY; without even the
-# implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
-# See the License for more information.
-#=============================================================================
+#  SYSTEMD_INCLUDE_DIRS - where to find systemd/sd-journal.h, etc.
+#  SYSTEMD_LIBRARIES    - List of libraries when using libsystemd.
+#  SYSTEMD_FOUND        - True if libsystemd is found.
 
-include(FeatureSummary)
-set_package_properties(Systemd PROPERTIES
-   URL "http://freedesktop.org/wiki/Software/systemd/"
-   DESCRIPTION "System and Service Manager")
+pkg_search_module(PC_SYSTEMD QUIET libsystemd)
 
-find_package(PkgConfig)
-pkg_check_modules(PC_SYSTEMD QUIET libsystemd)
-find_library(SYSTEMD_LIBRARIES NAMES systemd ${PC_SYSTEMD_LIBRARY_DIRS})
-find_path(SYSTEMD_INCLUDE_DIRS systemd/sd-login.h HINTS ${PC_SYSTEMD_INCLUDE_DIRS})
+find_path(SYSTEMD_INCLUDE_DIR
+  NAMES
+    systemd/sd-journal.h
+  HINTS
+    ${PC_SYSTEMD_INCLUDE_DIRS}
+)
 
-set(SYSTEMD_DEFINITIONS ${PC_SYSTEMD_CFLAGS_OTHER})
+find_library(SYSTEMD_LIBRARY
+  NAMES
+    systemd
+  HINTS
+    ${PC_SYSTEMD_LIBRARY_DIRS}
+)
 
 include(FindPackageHandleStandardArgs)
-find_package_handle_standard_args(SYSTEMD DEFAULT_MSG SYSTEMD_LIBRARIES SYSTEMD_INCLUDE_DIRS)
-mark_as_advanced(SYSTEMD_INCLUDE_DIRS SYSTEMD_LIBRARIES SYSTEMD_DEFINITIONS)
+find_package_handle_standard_args(SYSTEMD
+  REQUIRED_VARS   SYSTEMD_LIBRARY SYSTEMD_INCLUDE_DIR
+  VERSION_VAR     PC_SYSTEMD_VERSION)
+
+if(SYSTEMD_FOUND)
+  set(SYSTEMD_LIBRARIES ${SYSTEMD_LIBRARY})
+  set(SYSTEMD_INCLUDE_DIRS ${SYSTEMD_INCLUDE_DIR})
+else()
+  set(SYSTEMD_LIBRARIES)
+  set(SYSTEMD_INCLUDE_DIRS)
+endif()
+
+mark_as_advanced(SYSTEMD_LIBRARIES SYSTEMD_INCLUDE_DIRS)
diff --git a/extcap/CMakeLists.txt b/extcap/CMakeLists.txt
index d0ae9cbec3..3e59e7df90 100644
--- a/extcap/CMakeLists.txt
+++ b/extcap/CMakeLists.txt
@@ -257,11 +257,8 @@ if(BUILD_sdjournal AND SYSTEMD_FOUND)
 	set_extcap_executable_properties(sdjournal)
 	target_link_libraries(sdjournal ${sdjournal_LIBS})
 	target_include_directories(sdjournal SYSTEM PRIVATE ${SYSTEMD_INCLUDE_DIRS})
-	target_compile_definitions(sdjournal PRIVATE ${SYSTEMD_DEFINITIONS})
 	install(TARGETS sdjournal RUNTIME DESTINATION ${EXTCAP_INSTALL_LIBDIR})
 	add_dependencies(extcaps sdjournal)
-elseif (BUILD_sdjournal)
-	#message( WARNING "Cannot find libsystemd, cannot build sdjournal" )
 endif()
 
 #