Core/Build: Add the possibility to link libraries dynamically.

* makes it possible to access exported singletons from other shared lib's.
* reduces binary size

CMakeLists.txt

@@ -24,9 +24,6 @@ endif(POLICY CMP0043)
 set(CMAKE_DISABLE_SOURCE_CHANGES ON)
 set(CMAKE_DISABLE_IN_SOURCE_BUILD ON)
 
-# build static libraries
-set(BUILD_SHARED_LIBS OFF)
-
 # Set RPATH-handing (CMake parameters)
 set(CMAKE_SKIP_BUILD_RPATH 0)
 set(CMAKE_BUILD_WITH_INSTALL_RPATH 0)

cmake/compiler/clang/settings.cmake

@@ -18,3 +18,16 @@ endif()
 # -Wno-deprecated-register is needed to suppress 185 gsoap warnings on Unix systems.
 set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11 -Wno-narrowing -Wno-deprecated-register")
 set(CMAKE_CXX_FLAGS_DEBUG "${CMAKE_CXX_FLAGS_DEBUG} -DDEBUG=1")
+
+if (WITH_DYNAMIC_LINKING)
+  # -fPIC is needed to allow static linking in shared libs.
+  # -fvisibility=hidden sets the default visibility to hidden to prevent exporting of all symbols.
+  set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -fPIC -fvisibility=hidden")
+  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fPIC -fvisibility=hidden")
+
+  # --no-undefined to throw errors when there are undefined symbols
+  # (caused through missing TRINITY_*_API macros).
+  set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} --no-undefined")
+
+  message(STATUS "Clang: Disallow undefined symbols")
+endif()

cmake/compiler/gcc/settings.cmake

@@ -34,3 +34,15 @@ if( WITH_COREDEBUG )
   set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -g3")
   message(STATUS "GCC: Debug-flags set (-g3)")
 endif()
+
+if (WITH_DYNAMIC_LINKING)
+  set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -fPIC -fvisibility=hidden -Wno-attributes")
+  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fPIC -fvisibility=hidden -Wno-attributes")
+
+  # Should break the build when there are TRINITY_*_API macros missing
+  # but it complains about missing references in precompiled headers.
+  # set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -Wl,--no-undefined")
+  # set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wl,--no-undefined")
+
+  message(STATUS "GCC: Enabled shared linking")
+endif()

cmake/compiler/msvc/settings.cmake

@@ -74,6 +74,13 @@ if(NOT WITH_WARNINGS)
   message(STATUS "MSVC: Disabled generic compiletime warnings")
 endif()
 
+if (WITH_DYNAMIC_LINKING)
+  # C4251: needs to have dll-interface to be used by clients of class '...'
+  # C4275: non dll-interface class ...' used as base for dll-interface class '...'
+  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} /wd4251 /wd4275")
+  message(STATUS "MSVC: Enabled shared linking")
+endif()
+
 # Specify the maximum PreCompiled Header memory allocation limit
 # Fixes a compiler-problem when using PCH - the /Ym flag is adjusted by the compiler in MSVC2012, hence we need to set an upper limit with /Zm to avoid discrepancies)
 # (And yes, this is a verified , unresolved bug with MSVC... *sigh*)

cmake/options.cmake

@@ -13,6 +13,7 @@ option(SCRIPTS          "Build core with scripts included"
 option(TOOLS            "Build map/vmap/mmap extraction/assembler tools"              0)
 option(USE_SCRIPTPCH    "Use precompiled headers when compiling scripts"              1)
 option(USE_COREPCH      "Use precompiled headers when compiling servers"              1)
+option(WITH_DYNAMIC_LINKING "Enable dynamic library linking."                         0)
 option(WITH_WARNINGS    "Show all warnings during compile"                            0)
 option(WITH_COREDEBUG   "Include additional debug-code in core"                       0)
 set(WITH_SOURCE_TREE "no" CACHE STRING "Build the source tree for IDE's.")

cmake/showoptions.cmake

@@ -130,5 +130,14 @@ if ( HELGRIND )
   add_definitions(-DHELGRIND)
 endif()
 
+if (WITH_DYNAMIC_LINKING)
+  message("")
+  message(" *** WITH_DYNAMIC_LINKING - INFO!")
+  message(" *** Will link against shared libraries!")
+  message(" *** Please note that this is an experimental feature!")
+  add_definitions(-DTRINITY_API_USE_DYNAMIC_LINKING)
+  set(BUILD_SHARED_LIBS ON)
+else()
+  set(BUILD_SHARED_LIBS OFF)
+endif()
 message("")
-

src/common/Define.h

@@ -95,6 +95,45 @@
 #endif
 #endif //COMPILER == COMPILER_GNU
 
+#ifdef TRINITY_API_USE_DYNAMIC_LINKING
+#  if COMPILER == COMPILER_MICROSOFT
+#    define TC_API_EXPORT __declspec(dllexport)
+#    define TC_API_IMPORT __declspec(dllimport)
+#  elif COMPILER == COMPILER_GNU
+#    define TC_API_EXPORT __attribute__((visibility("default")))
+#    define TC_API_IMPORT
+#  else
+#    error compiler not supported!
+#  endif
+#else
+#  define TC_API_EXPORT
+#  define TC_API_IMPORT
+#endif
+
+#ifdef TRINITY_API_EXPORT_COMMON
+#  define TC_COMMON_API TC_API_EXPORT
+#else
+#  define TC_COMMON_API TC_API_IMPORT
+#endif
+
+#ifdef TRINITY_API_EXPORT_DATABASE
+#  define TC_DATABASE_API TC_API_EXPORT
+#else
+#  define TC_DATABASE_API TC_API_IMPORT
+#endif
+
+#ifdef TRINITY_API_EXPORT_SHARED
+#  define TC_SHARED_API TC_API_EXPORT
+#else
+#  define TC_SHARED_API TC_API_IMPORT
+#endif
+
+#ifdef TRINITY_API_EXPORT_GAME
+#  define TC_GAME_API TC_API_EXPORT
+#else
+#  define TC_GAME_API TC_API_IMPORT
+#endif
+
 #define UI64FMTD "%" PRIu64
 #define UI64LIT(N) UINT64_C(N)