build: require CMake 3.12, resolve circular dependency

In order to resolve the circular dependency, we need to annotate the
respective static libraries as "object" libraries.

This requires cmake 3.12, where Debian 10 (old old stable) and Ubuntu
20.04 have 3.13 and 3.16 respectively.

Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>

CMakeLists.txt

@@ -19,7 +19,7 @@
 # along with WeeChat.  If not, see <https://www.gnu.org/licenses/>.
 #
 
-cmake_minimum_required(VERSION 3.5)
+cmake_minimum_required(VERSION 3.12)
 
 project(weechat C)
 
@@ -242,14 +242,12 @@ endif()
 # Check for CURL
 find_package(CURL REQUIRED)
 
-# weechat_gui_common MUST be the first lib in the list
-set(STATIC_LIBS weechat_gui_common)
+set(STATIC_LIBS weechat_plugins)
 
 find_library(DL_LIBRARY
   NAMES dl
   PATHS /lib /usr/lib /usr/libexec /usr/local/lib /usr/local/libexec
 )
-list(APPEND STATIC_LIBS weechat_plugins)
 if(DL_LIBRARY)
   string(REGEX REPLACE "/[^/]*$" "" DL_LIBRARY_PATH "${DL_LIBRARY}")
   set(CMAKE_C_LINK_FLAGS "${CMAKE_C_LINK_FLAGS} -L${DL_LIBRARY_PATH}")

src/core/CMakeLists.txt

@@ -100,6 +100,6 @@ if(ENABLE_CJSON)
 endif()
 
 include_directories("${CMAKE_BINARY_DIR}")
-add_library(weechat_core STATIC ${LIB_CORE_SRC})
+add_library(weechat_core OBJECT ${LIB_CORE_SRC})
 target_link_libraries(weechat_core coverage_config)
 add_dependencies(weechat_core version_git)

src/gui/CMakeLists.txt

@@ -43,7 +43,7 @@ set(LIB_GUI_COMMON_SRC
 )
 
 include_directories("${CMAKE_BINARY_DIR}")
-add_library(weechat_gui_common STATIC ${LIB_GUI_COMMON_SRC})
+add_library(weechat_gui_common OBJECT ${LIB_GUI_COMMON_SRC})
 target_link_libraries(weechat_gui_common coverage_config)
 list(APPEND STATIC_LIBS weechat_gui_common)
 

src/gui/curses/headless/CMakeLists.txt

@@ -55,9 +55,7 @@ add_dependencies(${EXECUTABLE}
   weechat_ncurses_fake
 )
 
-# Due to circular references, we must link two times with libweechat_core.a and libweechat_gui_common.a
 target_link_libraries(${EXECUTABLE}
-  ${STATIC_LIBS}
   weechat_gui_headless
   weechat_ncurses_fake
   ${EXTRA_LIBS}

src/gui/curses/normal/CMakeLists.txt

@@ -58,8 +58,12 @@ add_dependencies(${EXECUTABLE} weechat_gui_curses_normal)
 
 list(APPEND EXTRA_LIBS ${NCURSES_LIBRARY})
 
-# Due to circular references, we must link two times with libweechat_core.a and libweechat_gui_common.a
-target_link_libraries(${EXECUTABLE} ${STATIC_LIBS} weechat_gui_curses_normal ${EXTRA_LIBS} ${STATIC_LIBS} coverage_config)
+target_link_libraries(${EXECUTABLE}
+  weechat_gui_curses_normal
+  ${EXTRA_LIBS}
+  ${STATIC_LIBS}
+  coverage_config
+)
 
 # Create a symbolic link weechat-curses -> weechat
 # This link is created for compatibility with old versions on /upgrade.

tests/CMakeLists.txt

@@ -226,8 +226,6 @@ target_link_libraries(tests
   weechat_gui_headless
   weechat_ncurses_fake
   weechat_unit_tests_core
-  # due to circular references, we must link two times with libweechat_core.a
-  weechat_core
   ${EXTRA_LIBS}
   ${CURL_LIBRARIES}
   ${ZLIB_LIBRARY}