Reduce warnings from moc-generated code

- The auto-generated code produces a lot of warnings from
   Clang 8; this obscures the more meaningful warnings from
   actual Calamares code, so tone the warnings down.
 - For Clang, set CALAMARES_MOC_OPTIONS.
 - Add convenience CMake function for automoccing. It applies
   the options as needed to a given target.

CMakeLists.txt

@@ -208,6 +208,8 @@ if( CMAKE_CXX_COMPILER_ID MATCHES "Clang" )
     set( CMAKE_TOOLCHAIN_PREFIX "llvm-" )
 
     set( CMAKE_SHARED_LINKER_FLAGS "-Wl,--no-undefined" )
+    
+    set( CALAMARES_AUTOMOC_OPTIONS "-butils/moc-warnings.h" )
 else()
     set( CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wl,--no-undefined" )
     set( CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wl,--fatal-warnings -Wnon-virtual-dtor -Woverloaded-virtual -Werror=return-type" )
@@ -509,6 +511,7 @@ install(
         "CMakeModules/CalamaresAddLibrary.cmake"
         "CMakeModules/CalamaresAddBrandingSubdirectory.cmake"
         "CMakeModules/CalamaresAddTranslations.cmake"
+        "CMakeModules/CalamaresAutomoc.cmake"
         "CMakeModules/CMakeColors.cmake"
     DESTINATION
         "${CMAKE_INSTALL_CMAKEDIR}"

CMakeModules/CalamaresAddLibrary.cmake

@@ -44,6 +44,7 @@
 # flag (i.e. `-D`) so only state the name (optionally, also the value)
 # without a `-D` prefixed to it. Pass in a CMake list as needed.
 include( CMakeParseArguments )
+include( CalamaresAutomoc )
 
 function(calamares_add_library)
     # parse arguments (name needs to be saved before passing ARGN into the macro)
@@ -81,9 +82,7 @@ function(calamares_add_library)
         add_library(${target} SHARED ${LIBRARY_SOURCES})
     endif()
 
-    # definitions - can this be moved into set_target_properties below?
+    calamares_automoc(${target})
-    add_definitions(${QT_DEFINITIONS})
-    set_target_properties(${target} PROPERTIES AUTOMOC TRUE)
     
     if(LIBRARY_EXPORT_MACRO)
         set_target_properties(${target} PROPERTIES COMPILE_DEFINITIONS ${LIBRARY_EXPORT_MACRO})

CMakeModules/CalamaresAutomoc.cmake

@@ -0,0 +1,36 @@
+# === This file is part of Calamares - <https://github.com/calamares> ===
+#
+#   Calamares is free software: you can redistribute it and/or modify
+#   it under the terms of the GNU General Public License as published by
+#   the Free Software Foundation, either version 3 of the License, or
+#   (at your option) any later version.
+#
+#   Calamares is distributed in the hope that it will be useful,
+#   but WITHOUT ANY WARRANTY; without even the implied warranty of
+#   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+#   GNU General Public License for more details.
+#
+#   You should have received a copy of the GNU General Public License
+#   along with Calamares. If not, see <http://www.gnu.org/licenses/>.
+#
+#   SPDX-License-Identifier: GPL-3.0+
+#   License-Filename: LICENSE
+#
+###
+#
+# Helper function for doing automoc on a target.
+#
+# Sets AUTOMOC TRUE for a target.
+#
+# If the global variable CALAMARES_AUTOMOC_OPTIONS is set, uses that
+# as well to set options passed to MOC. This can be used to add
+# libcalamares/utils/moc-warnings.h file to the moc, which in turn
+# reduces compiler warnings in generated MOC code.
+#
+
+function(calamares_automoc TARGET)
+    set_target_properties( ${TARGET} PROPERTIES AUTOMOC TRUE )
+    if ( CALAMARES_AUTOMOC_OPTIONS )
+        set_target_properties( ${TARGET} PROPERTIES AUTOMOC_MOC_OPTIONS "${CALAMARES_AUTOMOC_OPTIONS}" )
+    endif()
+endfunction()

src/libcalamares/CMakeLists.txt

@@ -84,10 +84,10 @@ endif()
 add_library( calamares SHARED ${libSources} ${kdsagSources} ${utilsSources} )
 set_target_properties( calamares
     PROPERTIES
-        AUTOMOC TRUE
         VERSION ${CALAMARES_VERSION_SHORT}
         SOVERSION ${CALAMARES_VERSION_SHORT}
 )
+calamares_automoc( calamares )
 
 target_link_libraries( calamares
     LINK_PRIVATE
@@ -114,7 +114,7 @@ if ( ECM_FOUND AND BUILD_TESTING )
             Qt5::Core
             Qt5::Test
     )
-    set_target_properties( libcalamarestest PROPERTIES AUTOMOC TRUE )
+    calamares_automoc( libcalamarestest )
 endif()
 
 # Make symlink lib/calamares/libcalamares.so to lib/libcalamares.so.VERSION so

src/libcalamares/utils/moc-warnings.h

@@ -0,0 +1,4 @@
+#ifdef __clang__
+#pragma clang diagnostic ignored "-Wextra-semi-stmt"
+#pragma clang diagnostic ignored "-Wredundant-parens"
+#endif