Approach to enable static linkage

Linking statically might be useful, especially
when linking Windows applications since MinGW
is less buggy then.

CMakeLists.txt

@@ -73,6 +73,7 @@ set(CMAKE_MODULE_FILES
     cmake/modules/Doxygen.cmake
     cmake/modules/ListToString.cmake
     cmake/modules/ShellCompletion.cmake
+    cmake/modules/3rdParty.cmake
 )
 set(CMAKE_TEMPLATE_FILES
     cmake/templates/Config.cmake.in
@@ -100,7 +101,7 @@ set(META_PROJECT_VARNAME CPP_UTILITIES)
 set(META_APP_NAME "C++ Utilities")
 set(META_APP_AUTHOR "Martchus")
 set(META_APP_URL "https://github.com/${META_APP_AUTHOR}/${META_PROJECT_NAME}")
-set(META_APP_DESCRIPTION "Common C++ classes and routines used by my applications such as argument parser, IO and conversion utilities.")
+set(META_APP_DESCRIPTION "Common C++ classes and routines used by my applications such as argument parser, IO and conversion utilities")
 set(META_VERSION_MAJOR 4)
 set(META_VERSION_MINOR 0)
 set(META_VERSION_PATCH 0)

cmake/modules/3rdParty.cmake

@@ -0,0 +1,63 @@
+if(NOT DEFINED EXTERNAL_LIBRARIES_EXISTS)
+    set(EXTERNAL_LIBRARIES_EXISTS true)
+    macro(use_external_library_from_package NAME VERSION INCLUDE_VAR LIBRARY_VAR LINKAGE REQUIRED)
+        # need to set CMAKE_FIND_LIBRARY_SUFFIXES temporarily to be able to find static libs, save the current value to be able to restore
+        set(DEFAULT_CMAKE_FIND_LIBRARY_SUFFIXES ${CMAKE_FIND_LIBRARY_SUFFIXES})
+
+        # handle arguments VERSION and REQUIRED
+        if("${VERSION}" STREQUAL "ANY_VERSION")
+            set(${NAME}_COMPATIBLE_VERSION "")
+        else()
+            set(${NAME}_COMPATIBLE_VERSION ${VERSION})
+        endif()
+        if("${REQUIRED}" STREQUAL "OPTIONAL")
+            set(${NAME}_REQUIRED "")
+        elseif("${REQUIRED}" STREQUAL "REQUIRED")
+            set(${NAME}_REQUIRED "REQUIRED")
+        else()
+            message(FATAL_ERROR "Invalid use of use_external_library; must specify either REQUIRED or OPTIONAL.")
+        endif()
+
+        # find dynamic library
+        if(WIN32)
+            set(CMAKE_FIND_LIBRARY_SUFFIXES .so)
+        else()
+            set(CMAKE_FIND_LIBRARY_SUFFIXES .dll.a .dll)
+        endif()
+        find_package(${NAME} ${${NAME}_COMPATIBLE_VERSION})
+        include_directories(${${INCLUDE_VAR}})
+        set(${NAME}_DYNAMIC_LIB ${${LIBRARY_VAR}})
+        set(${${LIBRARY_VAR}} "")
+
+        # find static library
+        if(WIN32)
+            set(CMAKE_FIND_LIBRARY_SUFFIXES .lib .a)
+        else()
+            set(CMAKE_FIND_LIBRARY_SUFFIXES .a)
+        endif()
+        find_package(${NAME} ${${NAME}_COMPATIBLE_VERSION})
+        set(${NAME}_STATIC_LIB ${${LIBRARY_VAR}})
+
+        # add library to list of libraries to link against when building dynamic libraries or applications
+        if(${NAME}_STATIC_LIB AND (("${LINKAGE}" STREQUAL "AUTO_LINKAGE" AND ((STATIC_LINKAGE AND "${META_PROJECT_TYPE}" STREQUAL "application") OR (STATIC_LIBRARY_LINKAGE AND ("${META_PROJECT_TYPE}" STREQUAL "" OR "${META_PROJECT_TYPE}" STREQUAL "library")))) OR ("${LINKAGE}" STREQUAL "STATIC")))
+            list(APPEND LIBRARIES ${${NAME}_STATIC_LIB})
+            message(STATUS "Linking ${META_PROJECT_NAME} statically against external library ${NAME}.")
+        elseif(${NAME}_DYNAMIC_LIB AND ("${LINKAGE}" STREQUAL "AUTO_LINKAGE" OR ("${LINKAGE}" STREQUAL "SHARED")))
+            list(APPEND LIBRARIES ${${NAME}_DYNAMIC_LIB})
+            message(STATUS "Linking ${META_PROJECT_NAME} dynamically against external library ${NAME}.")
+        else()
+            if(${REQUIRED})
+                message(FATAL_ERROR "External library ${NAME} required by ${META_PROJECT_NAME} is not available for the specified linkage ${LINKAGE}.")
+            else()
+                message(WARNING "External library ${NAME} required by ${META_PROJECT_NAME} is not available for the specified linkage ${LINKAGE}.")
+            endif()
+        endif()
+
+        # add library to list of libraries to be provided as transitive dependencies when building static libraries
+        list(APPEND STATIC_LIBRARIES ${${LIBRARY_VAR}})
+
+        # restore altered CMAKE_FIND_LIBRARY_SUFFIXES
+        set(CMAKE_FIND_LIBRARY_SUFFIXES ${DEFAULT_CMAKE_FIND_LIBRARY_SUFFIXES})
+        set(DEFAULT_CMAKE_FIND_LIBRARY_SUFFIXES "")
+    endmacro()
+endif()

cmake/modules/AppTarget.cmake

@@ -1,9 +1,9 @@
 # before including this module, BasicConfig must be included
 
-# set the windows extension to "exe", this is required by the mingw-w64 specific WindowsResources module
-if(MINGW)
+# set the windows extension to "exe", this is required by the Windows specific WindowsResources module
+if(WIN32)
     set(WINDOWS_EXT "exe")
-endif(MINGW)
+endif(WIN32)
 
 # add target for building the application
 add_executable(${TARGET_PREFIX}${META_PROJECT_NAME}${TARGET_SUFFIX} ${GUI_TYPE} ${HEADER_FILES} ${SRC_FILES} ${WIDGETS_FILES} ${QML_FILES} ${RES_FILES} ${QM_FILES} ${WINDOWS_ICON_PATH})

cmake/modules/BasicConfig.cmake

@@ -69,3 +69,7 @@ if(LOGGING_ENABLED)
     add_definitions(-DLOGGING_ENABLED)
     message(STATUS "Logging is enabled.")
 endif()
+
+# options for forcing static linkage when building applications or dynamic libraries
+option(STATIC_LINKAGE "forces static linkage when building applications" OFF)
+option(STATIC_LIBRARY_LINKAGE "forces static linkage when building dynamic libraries" OFF)

cmake/modules/LibraryTarget.cmake

@@ -25,27 +25,6 @@ set(LIB_INSTALL_DESTINATION "${CMAKE_INSTALL_PREFIX}/lib${SELECTED_LIB_SUFFIX}")
 set(CMAKE_MODULE_INSTALL_DESTINATION "${CMAKE_INSTALL_PREFIX}/share/${META_PROJECT_NAME}/cmake/modules")
 set(CMAKE_CONFIG_INSTALL_DESTINATION "${CMAKE_INSTALL_PREFIX}/share/${META_PROJECT_NAME}/cmake")
 
-# create the CMake config file from the template
-configure_package_config_file(
-    "${CONFIG_TEMPLATE_FILE}"
-    "${CMAKE_CURRENT_BINARY_DIR}/${META_PROJECT_NAME}Config.cmake"
-    INSTALL_DESTINATION
-        "${CMAKE_CONFIG_INSTALL_DESTINATION}"
-    PATH_VARS
-        CMAKE_MODULE_INSTALL_DESTINATION
-        CMAKE_CONFIG_INSTALL_DESTINATION
-        HEADER_INSTALL_DESTINATION
-        BIN_INSTALL_DESTINATION
-        LIB_INSTALL_DESTINATION
-)
-
-# write the CMake version config file
-write_basic_package_version_file(
-    ${CMAKE_CURRENT_BINARY_DIR}/${META_PROJECT_NAME}ConfigVersion.cmake
-    VERSION "${META_VERSION_MAJOR}.${META_VERSION_MINOR}.${META_VERSION_PATCH}"
-    COMPATIBILITY SameMajorVersion
-)
-
 # remove library prefix when building with mingw-w64 (just for consistency with qmake)
 if(MINGW)
     set(CMAKE_SHARED_LIBRARY_PREFIX "")
@@ -77,15 +56,37 @@ endif()
 if(BUILD_STATIC_LIBS)
     add_library(${TARGET_PREFIX}${META_PROJECT_NAME}${TARGET_SUFFIX}_static STATIC ${HEADER_FILES} ${SRC_FILES} ${WIDGETS_FILES} ${QML_FILES} ${RES_FILES} ${QM_FILES} ${WINDOWS_ICON_PATH})
     # add target link libraries for the static lib also because otherwise Qt header files can not be located
-    target_link_libraries(${TARGET_PREFIX}${META_PROJECT_NAME}${TARGET_SUFFIX}_static ${LIBRARIES})
+    target_link_libraries(${TARGET_PREFIX}${META_PROJECT_NAME}${TARGET_SUFFIX}_static ${STATIC_LIBRARIES})
     set_target_properties(${TARGET_PREFIX}${META_PROJECT_NAME}${TARGET_SUFFIX}_static PROPERTIES
         VERSION ${META_VERSION_MAJOR}.${META_VERSION_MINOR}.${META_VERSION_PATCH}
         SOVERSION ${META_VERSION_MAJOR}
         OUTPUT_NAME ${TARGET_PREFIX}${META_PROJECT_NAME}${TARGET_SUFFIX}
         CXX_STANDARD 11
     )
+    set(META_LIB_DEPENDS ${${TARGET_PREFIX}${META_PROJECT_NAME}${TARGET_SUFFIX}_static_LIB_DEPENDS}) # used in config file
 endif()
 
+# create the CMake config file from the template
+configure_package_config_file(
+    "${CONFIG_TEMPLATE_FILE}"
+    "${CMAKE_CURRENT_BINARY_DIR}/${META_PROJECT_NAME}Config.cmake"
+    INSTALL_DESTINATION
+        "${CMAKE_CONFIG_INSTALL_DESTINATION}"
+    PATH_VARS
+        CMAKE_MODULE_INSTALL_DESTINATION
+        CMAKE_CONFIG_INSTALL_DESTINATION
+        HEADER_INSTALL_DESTINATION
+        BIN_INSTALL_DESTINATION
+        LIB_INSTALL_DESTINATION
+)
+
+# write the CMake version config file
+write_basic_package_version_file(
+    ${CMAKE_CURRENT_BINARY_DIR}/${META_PROJECT_NAME}ConfigVersion.cmake
+    VERSION "${META_VERSION_MAJOR}.${META_VERSION_MINOR}.${META_VERSION_PATCH}"
+    COMPATIBILITY SameMajorVersion
+)
+
 # add install target for the CMake config files
 install(
     FILES

cmake/templates/Config.cmake.in

@@ -1,6 +1,10 @@
 @PACKAGE_INIT@
 
+set(@META_PROJECT_VARNAME@_HAS_LIBS "@BUILD_SHARED_LIBS@")
 set(@META_PROJECT_VARNAME@_LIBS "@META_PROJECT_NAME@")
+set(@META_PROJECT_VARNAME@_HAS_STATIC_LIBS "@BUILD_STATIC_LIBS@")
+set(@META_PROJECT_VARNAME@_STATIC_LIBS "@META_PROJECT_NAME@.a")
+set(@META_PROJECT_VARNAME@_STATIC_LIBS_DEPENDS @META_LIB_DEPENDS@)
 set(@META_PROJECT_VARNAME@_INCLUDE_DIRS "@PACKAGE_HEADER_INSTALL_DESTINATION@")
 set(@META_PROJECT_VARNAME@_BIN_DIR "@PACKAGE_BIN_INSTALL_DESTINATION@")
 set(@META_PROJECT_VARNAME@_LIB_DIR "@PACKAGE_LIB_INSTALL_DESTINATION@")
@@ -10,6 +14,16 @@ set(@META_PROJECT_VARNAME@_CONFIG_DIRS "@PACKAGE_CMAKE_CONFIG_INSTALL_DESTINATIO
 macro(use_@META_PROJECT_VARNAME@)
     include_directories(BEFORE SYSTEM ${@META_PROJECT_VARNAME@_INCLUDE_DIRS})
     link_directories(${@META_PROJECT_VARNAME@_LIB_DIR})
-    list(APPEND LIBRARIES ${@META_PROJECT_VARNAME@_LIBS})
+    # add library to list of libraries to link against when building dynamic libraries or applications
+    if(@META_PROJECT_VARNAME@_HAS_STATIC_LIBS AND ((NOT ARGV0 AND ((STATIC_LINKAGE AND "${META_PROJECT_TYPE}" STREQUAL "application") OR (STATIC_LIBRARY_LINKAGE AND ("${META_PROJECT_TYPE}" STREQUAL "" OR "${META_PROJECT_TYPE}" STREQUAL "library")))) OR ("${ARGV0}" STREQUAL "STATIC")))
+        list(APPEND LIBRARIES ${@META_PROJECT_VARNAME@_STATIC_LIBS} ${@META_PROJECT_VARNAME@_STATIC_LIBS_DEPENDS})
+    elseif(@META_PROJECT_VARNAME@_HAS_LIBS AND (NOT ARGV0 OR ("${ARGV0}" STREQUAL "SHARED")))
+        list(APPEND LIBRARIES ${@META_PROJECT_VARNAME@_LIBS})
+    else()
+        message(ERROR "Specified linkage ${ARGV0} is not available.")
+    endif()
+    # add library to list of libraries to be provided as transitive dependencies when building static libraries
+    list(APPEND STATIC_LIBRARIES ${@META_PROJECT_VARNAME@_STATIC_LIBS} ${@META_PROJECT_VARNAME@_STATIC_LIBS_DEPENDS})
+    # make CMake modules of the project available
     list(APPEND CMAKE_MODULE_PATH ${@META_PROJECT_VARNAME@_MODULE_DIRS})
 endmacro()