Allow override of BUILD_SHARED_LIBS

The cmake option BUILD_SHARED_LIBS is a cmake built-in option
to control if libraries are by default SHARED or STATIC.

For large projects, it is desired to be able to design gtsam as a
shared or static library regardless of the value of BUILD_SHARED_LIBS.
This change is unobtrusive, two new cmake options are created, to
force gtsam to be a shared or static library. If neither option is
set (this is the default), the behavior of gtsam remains unchanged
which is to use BUILD_SHARED_LIBS decision.

cmake/HandleEigen.cmake

@@ -82,7 +82,7 @@ else()
 endif ()
 
 if (MSVC)
-    if (BUILD_SHARED_LIBS)
+    if (GTSAM_LIBRARY_TYPE STREQUAL "SHARED")
         # mute eigen static assert to avoid errors in shared lib
         list_append_cache(GTSAM_COMPILE_DEFINITIONS_PUBLIC EIGEN_NO_STATIC_ASSERT)
     endif()

cmake/HandleGeneralOptions.cmake

@@ -14,7 +14,8 @@ if(GTSAM_UNSTABLE_AVAILABLE)
     option(GTSAM_UNSTABLE_BUILD_PYTHON       "Enable/Disable Python wrapper for libgtsam_unstable" ON)
     option(GTSAM_UNSTABLE_INSTALL_MATLAB_TOOLBOX "Enable/Disable MATLAB wrapper for libgtsam_unstable" OFF)
 endif()
-option(BUILD_SHARED_LIBS                    "Build shared gtsam library, instead of static" ON)
+option(GTSAM_FORCE_SHARED_LIB               "Force gtsam to be a shared library, overriding BUILD_SHARED_LIBS" OFF)
+option(GTSAM_FORCE_STATIC_LIB               "Force gtsam to be a static library, overriding BUILD_SHARED_LIBS" OFF)
 option(GTSAM_USE_QUATERNIONS                "Enable/Disable using an internal Quaternion representation for rotations instead of rotation matrices. If enable, Rot3::EXPMAP is enforced by default." OFF)
 option(GTSAM_POSE3_EXPMAP                   "Enable/Disable using Pose3::EXPMAP as the default mode. If disabled, Pose3::FIRST_ORDER will be used." ON)
 option(GTSAM_ROT3_EXPMAP                    "Ignore if GTSAM_USE_QUATERNIONS is OFF (Rot3::EXPMAP by default). Otherwise, enable Rot3::EXPMAP, or if disabled, use Rot3::CAYLEY." ON)
@@ -31,6 +32,24 @@ option(GTSAM_TANGENT_PREINTEGRATION         "Use new ImuFactor with integration
 option(GTSAM_SLOW_BUT_CORRECT_BETWEENFACTOR "Use the slower but correct version of BetweenFactor" OFF)
 option(GTSAM_ENABLE_BOOST_SERIALIZATION "Enable Boost serialization" ON)
 
+if (GTSAM_FORCE_SHARED_LIB)
+    message(STATUS "GTSAM is a shared library due to GTSAM_FORCE_SHARED_LIB")
+    set(GTSAM_LIBRARY_TYPE SHARED CACHE STRING "" FORCE)
+    set(GTSAM_SHARED_LIB 1 CACHE BOOL "" FORCE)
+elseif (GTSAM_FORCE_STATIC_LIB)
+    message(STATUS "GTSAM is a static library due to GTSAM_FORCE_STATIC_LIB")
+    set(GTSAM_LIBRARY_TYPE STATIC CACHE STRING "" FORCE)
+    set(GTSAM_SHARED_LIB 0 CACHE BOOL "" FORCE)
+elseif (BUILD_SHARED_LIBS)
+    message(STATUS "GTSAM is a shared library due to BUILD_SHARED_LIBS is ON")
+    set(GTSAM_LIBRARY_TYPE SHARED CACHE STRING "" FORCE)
+    set(GTSAM_SHARED_LIB 1 CACHE BOOL "" FORCE)
+else()
+    message(STATUS "GTSAM is a static library due to BUILD_SHARED_LIBS is OFF")
+    set(GTSAM_LIBRARY_TYPE STATIC CACHE STRING "" FORCE)
+    set(GTSAM_SHARED_LIB 0 CACHE BOOL "" FORCE)
+endif()
+
 #TODO(kartikarcot) defining it in config.h.in did not work
 if (GTSAM_ENABLE_BOOST_SERIALIZATION)
     add_definitions(-DGTSAM_ENABLE_BOOST_SERIALIZATION)

cmake/HandleGlobalBuildFlags.cmake

@@ -14,11 +14,11 @@ endif()
 # or explicit instantiation will generate build errors.
 # See: https://bitbucket.org/gtborg/gtsam/issues/417/fail-to-build-on-msvc-2017
 #
-if(MSVC AND BUILD_SHARED_LIBS)
+if(MSVC AND GTSAM_SHARED_LIB)
     list_append_cache(GTSAM_COMPILE_DEFINITIONS_PUBLIC EIGEN_NO_STATIC_ASSERT)
 endif()
 
-if (APPLE AND BUILD_SHARED_LIBS)
+if (APPLE AND GTSAM_SHARED_LIB)
     # Set the default install directory on macOS
     set(CMAKE_INSTALL_NAME_DIR "${CMAKE_INSTALL_PREFIX}/lib")
 endif()

cmake/HandlePrintConfiguration.cmake

@@ -14,7 +14,7 @@ print_enabled_config(${GTSAM_BUILD_TIMING_ALWAYS}         "Build timing scripts
 if (DOXYGEN_FOUND)
     print_enabled_config(${GTSAM_BUILD_DOCS}              "Build Docs")
 endif()
-print_enabled_config(${BUILD_SHARED_LIBS}                 "Build shared GTSAM libraries")
+print_enabled_config(${GTSAM_SHARED_LIB}                  "Build shared GTSAM libraries")
 print_enabled_config(${GTSAM_BUILD_TYPE_POSTFIXES}        "Put build type in library name")
 if(GTSAM_UNSTABLE_AVAILABLE)
     print_enabled_config(${GTSAM_BUILD_UNSTABLE}          "Build libgtsam_unstable        ")

cmake/dllexport.h.in

@@ -31,10 +31,10 @@
 
 // Whether GTSAM is compiled as static or DLL in windows. 
 // This will be used to decide whether include __declspec(dllimport) or not in headers
-#cmakedefine BUILD_SHARED_LIBS
+#cmakedefine GTSAM_SHARED_LIB
 
 #ifdef _WIN32
-#  ifndef BUILD_SHARED_LIBS
+#  ifndef GTSAM_SHARED_LIB
 #    define @library_name@_EXPORT
 #    define @library_name@_EXTERN_EXPORT extern
 #  else
@@ -56,5 +56,5 @@
 #endif
 #endif
 
-#undef BUILD_SHARED_LIBS
+#undef GTSAM_SHARED_LIB
 

gtsam/CMakeLists.txt

@@ -118,10 +118,11 @@ message(STATUS "GTSAM Version: ${gtsam_version}")
 message(STATUS "Install prefix: ${CMAKE_INSTALL_PREFIX}")
 
 # build shared and static versions of the library
-message(STATUS "Building GTSAM - shared: ${BUILD_SHARED_LIBS}")
+message(STATUS "Building GTSAM - as a ${GTSAM_LIBRARY_TYPE} library")
 
-# BUILD_SHARED_LIBS automatically defines static/shared libs:
-add_library(gtsam ${gtsam_srcs})
+# BUILD_SHARED_LIBS automatically defines static/shared libs
+# Here we ensure we control which type of library gtsam is specifically
+add_library(gtsam ${GTSAM_LIBRARY_TYPE} ${gtsam_srcs})
 target_link_libraries(gtsam PUBLIC ${GTSAM_BOOST_LIBRARIES})
 target_link_libraries(gtsam PUBLIC ${GTSAM_ADDITIONAL_LIBRARIES})
 
@@ -174,7 +175,7 @@ target_include_directories(gtsam SYSTEM BEFORE PUBLIC
 )
 
 if(WIN32) # Add 'lib' prefix to static library to avoid filename collision with shared library
-	if (NOT BUILD_SHARED_LIBS)
+	if (NOT GTSAM_SHARED_LIB)
 		set_target_properties(gtsam PROPERTIES
 			PREFIX "lib"
 			COMPILE_DEFINITIONS GTSAM_IMPORT_STATIC)

gtsam_unstable/CMakeLists.txt

@@ -87,8 +87,7 @@ set(gtsam_unstable_soversion ${GTSAM_VERSION_MAJOR})
 message(STATUS "GTSAM_UNSTABLE Version: ${gtsam_unstable_version}")
 message(STATUS "Install prefix: ${CMAKE_INSTALL_PREFIX}")
 
-# BUILD_SHARED_LIBS automatically defines static/shared libs:
-add_library(gtsam_unstable ${gtsam_unstable_srcs})
+add_library(gtsam_unstable ${GTSAM_LIBRARY_TYPE} ${gtsam_unstable_srcs})
 
 # Apply build flags:
 gtsam_apply_build_flags(gtsam_unstable)
@@ -102,7 +101,7 @@ target_link_libraries(gtsam_unstable PUBLIC gtsam)
 # No need to link against Boost here, it's inherited from gtsam PUBLIC interface
 
 if(WIN32) # Add 'lib' prefix to static library to avoid filename collision with shared library
-	if (NOT BUILD_SHARED_LIBS)
+	if (NOT GTSAM_SHARED_LIB)
 		set_target_properties(gtsam_unstable PROPERTIES
 			PREFIX "lib"
 			COMPILE_DEFINITIONS GTSAM_UNSTABLE_IMPORT_STATIC)

matlab/CMakeLists.txt

@@ -42,7 +42,7 @@ endif()
 
 include(MatlabWrap)
 
-if(NOT BUILD_SHARED_LIBS)
+if(NOT GTSAM_SHARED_LIB)
   message(
     FATAL_ERROR
       "GTSAM_INSTALL_MATLAB_TOOLBOX and BUILD_SHARED_LIBS=OFF."
@@ -54,7 +54,7 @@ endif()
 # ##############################################################################
 # Generate, build and install toolbox
 set(mexFlags "${GTSAM_BUILD_MEX_BINARY_FLAGS}")
-if(NOT BUILD_SHARED_LIBS)
+if(NOT GTSAM_SHARED_LIB)
   list(APPEND mexFlags -DGTSAM_IMPORT_STATIC)
 endif()
 
@@ -89,7 +89,7 @@ matlab_wrap("${interface_files}" "gtsam" "${GTSAM_ADDITIONAL_LIBRARIES}"
 if(GTSAM_UNSTABLE_INSTALL_MATLAB_TOOLBOX)
   # Generate, build and install toolbox
   set(mexFlags "${GTSAM_BUILD_MEX_BINARY_FLAGS}")
-  if(NOT BUILD_SHARED_LIBS)
+  if(NOT GTSAM_SHARED_LIB)
     list(APPEND mexFlags -DGTSAM_IMPORT_STATIC)
   endif()