More concretely utilize local modules in our CMake code. (#17022)

* Properly handle systemd.cmake as a module.

* Split CMake compiler flag handling functions to their own module.

* Add include guards to modules.

* Prefix module names with Netdata.

This ensures that we end up using our local modules instead of possibly
using a system module with the same name.

* Drop include guards.

And shift systemd detection code to a macro so it’s less dangerous to
import the module multiple times.

4 files changed, 121 insertions, 105 deletions

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 320a294e84..d6e9536bbc 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -56,6 +56,7 @@ project(netdata
         DESCRIPTION "Netdata real-time monitoring"
         HOMEPAGE_URL "https://www.netdata.cloud"
         LANGUAGES C CXX)
+list(APPEND CMAKE_MODULE_PATH "${PROJECT_SOURCE_DIR}/packaging/cmake/Modules")
 
 find_package(PkgConfig REQUIRED)
 
@@ -165,8 +166,7 @@ endif()
 # handling of extra compiler flags
 #
 
-include(CheckCCompilerFlag)
-include(CheckCXXCompilerFlag)
+include(NetdataCompilerFlags)
 
 # Disable hardening for debug builds by default.
 if(CMAKE_BUILD_TYPE STREQUAL "Debug")
@@ -175,71 +175,6 @@ else()
         option(DISABLE_HARDENING "disable adding extra compiler flags for hardening" FALSE)
 endif()
 
-# Construct a pre-processor safe name
-function(make_cpp_safe_name value target)
-        string(REPLACE "-" "_" tmp "${value}")
-        string(REPLACE "=" "_" tmp "${tmp}")
-        set(${target} "${tmp}" PARENT_SCOPE)
-endfunction()
-
-# Conditionally add an extra compiler flag to C and C++ flags.
-#
-# If the language flags already match the `match` argument, skip this flag.
-# Otherwise, check for support for `flag` and if support is found, add it to
-# the language-specific `target` flag group.
-function(add_simple_extra_compiler_flag match flag target)
-        set(CMAKE_REQUIRED_FLAGS "-Werror")
-
-        make_cpp_safe_name("${flag}" flag_name)
-
-        if(NOT ${CMAKE_C_FLAGS} MATCHES ${match})
-                check_c_compiler_flag("${flag}" HAVE_C_${flag_name})
-                if(HAVE_C_${flag_name})
-                        set(${target}_C_FLAGS "${${target}_C_FLAGS} ${flag}" PARENT_SCOPE)
-                endif()
-        endif()
-
-        if(NOT ${CMAKE_CXX_FLAGS} MATCHES ${match})
-                check_cxx_compiler_flag("${flag}" HAVE_CXX_${flag_name})
-                if(HAVE_CXX_${flag_name})
-                        set(${target}_CXX_FLAGS "${${target}_CXX_FLAGS} ${flag}" PARENT_SCOPE)
-                endif()
-        endif()
-endfunction()
-
-# Same as add_simple_extra_compiler_flag, but check for a second flag if the
-# first one is unsupported.
-function(add_double_extra_compiler_flag match flag1 flag2 target)
-        set(CMAKE_REQUIRED_FLAGS "-Werror")
-
-        make_cpp_safe_name("${flag1}" flag1_name)
-        make_cpp_safe_name("${flag2}" flag2_name)
-
-        if(NOT ${CMAKE_C_FLAGS} MATCHES ${match})
-                check_c_compiler_flag("${flag1}" HAVE_C_${flag1_name})
-                if(HAVE_C_${flag1_name})
-                        set(${target}_C_FLAGS "${${target}_C_FLAGS} ${flag1}" PARENT_SCOPE)
-                else()
-                        check_c_compiler_flag("${flag2}" HAVE_C_${flag2_name})
-                        if(HAVE_C_${flag2_name})
-                                set(${target}_C_FLAGS "${${target}_C_FLAGS} ${flag2}" PARENT_SCOPE)
-                        endif()
-                endif()
-        endif()
-
-        if(NOT ${CMAKE_CXX_FLAGS} MATCHES ${match})
-                check_cxx_compiler_flag("${flag1}" HAVE_CXX_${flag1_name})
-                if(HAVE_CXX_${flag1_name})
-                        set(${target}_CXX_FLAGS "${${target}_CXX_FLAGS} ${flag1}" PARENT_SCOPE)
-                else()
-                        check_cxx_compiler_flag("${flag2}" HAVE_CXX_${flag2_name})
-                        if(HAVE_CXX_${flag2_name})
-                                set(${target}_CXX_FLAGS "${${target}_CXX_FLAGS} ${flag2}" PARENT_SCOPE)
-                        endif()
-                endif()
-        endif()
-endfunction()
-
 set(EXTRA_HARDENING_C_FLAGS "")
 set(EXTRA_HARDENING_CXX_FLAGS "")
 
@@ -1524,7 +1459,8 @@ set_source_files_properties(JudyLTables.c PROPERTIES COMPILE_OPTIONS "-I${CMAKE_
 # build libnetdata
 #
 
-include(packaging/cmake/systemd.cmake)
+include(NetdataDetectSystemd)
+detect_systemd()
 
 add_library(libnetdata STATIC ${LIBNETDATA_FILES})
 
diff --git a/packaging/cmake/Modules/NetdataCompilerFlags.cmake b/packaging/cmake/Modules/NetdataCompilerFlags.cmake
new file mode 100644
index 0000000000..894e244ce6
--- /dev/null
+++ b/packaging/cmake/Modules/NetdataCompilerFlags.cmake
@@ -0,0 +1,75 @@
+# Functions to simplify handling of extra compiler flags.
+#
+# Copyright (c) 2024 Netdata Inc.
+# SPDX-License-Identifier: GPL-3.0-or-later
+
+include(CheckCCompilerFlag)
+include(CheckCXXCompilerFlag)
+
+# Construct a pre-processor safe name
+#
+# This takes a specified value, and assigns the generated name to the
+# specified target.
+function(make_cpp_safe_name value target)
+        string(REPLACE "-" "_" tmp "${value}")
+        string(REPLACE "=" "_" tmp "${tmp}")
+        set(${target} "${tmp}" PARENT_SCOPE)
+endfunction()
+
+# Conditionally add an extra compiler flag to C and C++ flags.
+#
+# If the language flags already match the `match` argument, skip this flag.
+# Otherwise, check for support for `flag` and if support is found, add it to
+# the language-specific `target` flag group.
+function(add_simple_extra_compiler_flag match flag target)
+        set(CMAKE_REQUIRED_FLAGS "-Werror")
+
+        make_cpp_safe_name("${flag}" flag_name)
+
+        if(NOT ${CMAKE_C_FLAGS} MATCHES ${match})
+                check_c_compiler_flag("${flag}" HAVE_C_${flag_name})
+                if(HAVE_C_${flag_name})
+                        set(${target}_C_FLAGS "${${target}_C_FLAGS} ${flag}" PARENT_SCOPE)
+                endif()
+        endif()
+
+        if(NOT ${CMAKE_CXX_FLAGS} MATCHES ${match})
+                check_cxx_compiler_flag("${flag}" HAVE_CXX_${flag_name})
+                if(HAVE_CXX_${flag_name})
+                        set(${target}_CXX_FLAGS "${${target}_CXX_FLAGS} ${flag}" PARENT_SCOPE)
+                endif()
+        endif()
+endfunction()
+
+# Same as add_simple_extra_compiler_flag, but check for a second flag if the
+# first one is unsupported.
+function(add_double_extra_compiler_flag match flag1 flag2 target)
+        set(CMAKE_REQUIRED_FLAGS "-Werror")
+
+        make_cpp_safe_name("${flag1}" flag1_name)
+        make_cpp_safe_name("${flag2}" flag2_name)
+
+        if(NOT ${CMAKE_C_FLAGS} MATCHES ${match})
+                check_c_compiler_flag("${flag1}" HAVE_C_${flag1_name})
+                if(HAVE_C_${flag1_name})
+                        set(${target}_C_FLAGS "${${target}_C_FLAGS} ${flag1}" PARENT_SCOPE)
+                else()
+                        check_c_compiler_flag("${flag2}" HAVE_C_${flag2_name})
+                        if(HAVE_C_${flag2_name})
+                                set(${target}_C_FLAGS "${${target}_C_FLAGS} ${flag2}" PARENT_SCOPE)
+                        endif()
+                endif()
+        endif()
+
+        if(NOT ${CMAKE_CXX_FLAGS} MATCHES ${match})
+                check_cxx_compiler_flag("${flag1}" HAVE_CXX_${flag1_name})
+                if(HAVE_CXX_${flag1_name})
+                        set(${target}_CXX_FLAGS "${${target}_CXX_FLAGS} ${flag1}" PARENT_SCOPE)
+                else()
+                        check_cxx_compiler_flag("${flag2}" HAVE_CXX_${flag2_name})
+                        if(HAVE_CXX_${flag2_name})
+                                set(${target}_CXX_FLAGS "${${target}_CXX_FLAGS} ${flag2}" PARENT_SCOPE)
+                        endif()
+                endif()
+        endif()
+endfunction()
diff --git a/packaging/cmake/Modules/NetdataDetectSystemd.cmake b/packaging/cmake/Modules/NetdataDetectSystemd.cmake
new file mode 100644
index 0000000000..5c0e6e09e5
--- /dev/null
+++ b/packaging/cmake/Modules/NetdataDetectSystemd.cmake
@@ -0,0 +1,42 @@
+# CMake Module to handle all the systemd-related checks for Netdata.
+#
+# Copyright (c) 2024 Netdata Inc.
+# SPDX-License-Identifier: GPL-3.0-or-later
+
+macro(detect_systemd)
+    find_library(SYSTEMD_LIBRARY NAMES systemd)
+
+    set(ENABLE_DSYSTEMD_DBUS NO)
+    pkg_check_modules(SYSTEMD libsystemd)
+
+    if(SYSTEMD_FOUND)
+        set(CMAKE_REQUIRED_LIBRARIES_BEFORE_SYSTEMD "${CMAKE_REQUIRED_LIBRARIES}")
+        set(CMAKE_REQUIRED_LIBRARIES "${CMAKE_REQUIRED_LIBRARIES};${SYSTEMD_LIBRARIES}")
+
+        check_c_source_compiles("
+        #include <systemd/sd-journal.h>
+
+        int main() {
+            int x = SD_JOURNAL_OS_ROOT;
+            return 0;
+        }" HAVE_SD_JOURNAL_OS_ROOT)
+
+        check_symbol_exists(SD_JOURNAL_OS_ROOT "systemd/sd-journal.h" HAVE_SD_JOURNAL_OS_ROOT)
+        check_symbol_exists(sd_journal_open_files_fd "systemd/sd-journal.h" HAVE_SD_JOURNAL_OPEN_FILES_FD)
+        check_symbol_exists(sd_journal_restart_fields "systemd/sd-journal.h" HAVE_SD_JOURNAL_RESTART_FIELDS)
+        check_symbol_exists(sd_journal_get_seqnum "systemd/sd-journal.h" HAVE_SD_JOURNAL_GET_SEQNUM)
+
+        check_symbol_exists(sd_bus_default_system "systemd/sd-bus.h" HAVE_SD_BUS_DEFAULT_SYSTEM)
+        check_symbol_exists(sd_bus_call_method "systemd/sd-bus.h" HAVE_SD_BUS_CALL_METHOD)
+        check_symbol_exists(sd_bus_message_enter_container "systemd/sd-bus.h" HAVE_SD_BUS_MESSAGE_ENTER_CONTAINER)
+        check_symbol_exists(sd_bus_message_read "systemd/sd-bus.h" HAVE_SD_BUS_MESSAGE_READ)
+        check_symbol_exists(sd_bus_message_exit_container "systemd/sd-bus.h" HAVE_SD_BUS_MESSAGE_EXIT_CONTAINER)
+
+        set(CMAKE_REQUIRED_LIBRARIES "${CMAKE_REQUIRED_LIBRARIES_BEFORE_SYSTEMD}")
+
+        set(HAVE_SYSTEMD True)
+        if(HAVE_SD_BUS_DEFAULT_SYSTEM AND HAVE_SD_BUS_CALL_METHOD AND HAVE_SD_BUS_MESSAGE_ENTER_CONTAINER AND HAVE_SD_BUS_MESSAGE_READ AND HAVE_SD_BUS_MESSAGE_EXIT_CONTAINER)
+            set(ENABLE_SYSTEMD_DBUS YES)
+        endif()
+    endif()
+endmacro()
diff --git a/packaging/cmake/systemd.cmake b/packaging/cmake/systemd.cmake
deleted file mode 100644
index b61cbb2a42..0000000000
--- a/packaging/cmake/systemd.cmake
+++ /dev/null
@@ -1,37 +0,0 @@
-find_library(SYSTEMD_LIBRARY NAMES systemd)
-
-include(CheckFunctionExists)
-
-set(ENABLE_DSYSTEMD_DBUS NO)
-pkg_check_modules(SYSTEMD libsystemd)
-
-if(SYSTEMD_FOUND)
-    set(CMAKE_REQUIRED_LIBRARIES_BEFORE_SYSTEMD "${CMAKE_REQUIRED_LIBRARIES}")
-    set(CMAKE_REQUIRED_LIBRARIES "${CMAKE_REQUIRED_LIBRARIES};${SYSTEMD_LIBRARIES}")
-
-    check_c_source_compiles("
-    #include <systemd/sd-journal.h>
-
-    int main() {
-        int x = SD_JOURNAL_OS_ROOT;
-        return 0;
-    }" HAVE_SD_JOURNAL_OS_ROOT)
-
-    check_symbol_exists(SD_JOURNAL_OS_ROOT "systemd/sd-journal.h" HAVE_SD_JOURNAL_OS_ROOT)
-    check_symbol_exists(sd_journal_open_files_fd "systemd/sd-journal.h" HAVE_SD_JOURNAL_OPEN_FILES_FD)
-    check_symbol_exists(sd_journal_restart_fields "systemd/sd-journal.h" HAVE_SD_JOURNAL_RESTART_FIELDS)
-    check_symbol_exists(sd_journal_get_seqnum "systemd/sd-journal.h" HAVE_SD_JOURNAL_GET_SEQNUM)
-
-    check_symbol_exists(sd_bus_default_system "systemd/sd-bus.h" HAVE_SD_BUS_DEFAULT_SYSTEM)
-    check_symbol_exists(sd_bus_call_method "systemd/sd-bus.h" HAVE_SD_BUS_CALL_METHOD)
-    check_symbol_exists(sd_bus_message_enter_container "systemd/sd-bus.h" HAVE_SD_BUS_MESSAGE_ENTER_CONTAINER)
-    check_symbol_exists(sd_bus_message_read "systemd/sd-bus.h" HAVE_SD_BUS_MESSAGE_READ)
-    check_symbol_exists(sd_bus_message_exit_container "systemd/sd-bus.h" HAVE_SD_BUS_MESSAGE_EXIT_CONTAINER)
-
-    set(CMAKE_REQUIRED_LIBRARIES "${CMAKE_REQUIRED_LIBRARIES_BEFORE_SYSTEMD}")
-
-    set(HAVE_SYSTEMD True)
-    if(HAVE_SD_BUS_DEFAULT_SYSTEM AND HAVE_SD_BUS_CALL_METHOD AND HAVE_SD_BUS_MESSAGE_ENTER_CONTAINER AND HAVE_SD_BUS_MESSAGE_READ AND HAVE_SD_BUS_MESSAGE_EXIT_CONTAINER)
-        set(ENABLE_SYSTEMD_DBUS YES)
-    endif()
-endif()