Problem: CMake rebuilds everything twice

Solution: build all the objects separately before the link step, to
avoid rebuilding when doing both static and shared builds

CMakeLists.txt

@@ -575,8 +575,6 @@ set (cxx-sources
         gather.cpp
 		zap_client.cpp)
 
-set (rc-sources version.rc)
-
 if (MINGW)
   # Generate the right type when using -m32 or -m64
   macro (set_rc_arch rc_target)
@@ -643,10 +641,7 @@ foreach (source ${cxx-sources})
   list (APPEND sources ${CMAKE_CURRENT_SOURCE_DIR}/src/${source})
 endforeach ()
 
-foreach (source ${rc-sources})
-  list (APPEND sources ${CMAKE_CURRENT_BINARY_DIR}/${source})
-  configure_file (${CMAKE_CURRENT_SOURCE_DIR}/src/${source}.in ${CMAKE_CURRENT_BINARY_DIR}/${source})
-endforeach ()
+configure_file (${CMAKE_CURRENT_SOURCE_DIR}/src/version.rc.in ${CMAKE_CURRENT_BINARY_DIR}/version.rc)
 
 #   Delete any src/platform.hpp left by configure
 file (REMOVE ${CMAKE_CURRENT_SOURCE_DIR}/src/platform.hpp)
@@ -751,12 +746,16 @@ if (BUILD_STATIC)
   list(APPEND target_outputs "libzmq-static")
 endif()
 
+# avoid building everything twice for shared + static
+add_library (objects OBJECT ${sources})
+set_property(TARGET objects PROPERTY POSITION_INDEPENDENT_CODE ON)
+
 if (MSVC)
   # Suppress linker warnings caused by #ifdef omission
   # of file content.
   set( CMAKE_STATIC_LINKER_FLAGS /ignore:4221 )
   if (BUILD_SHARED)
-    add_library (libzmq SHARED ${sources} ${public_headers} ${html-docs} ${readme-docs} ${CMAKE_CURRENT_BINARY_DIR}/NSIS.template.in)
+    add_library (libzmq SHARED $<TARGET_OBJECTS:objects> ${public_headers} ${html-docs} ${readme-docs} ${CMAKE_CURRENT_BINARY_DIR}/NSIS.template.in ${CMAKE_CURRENT_BINARY_DIR}/version.rc)
     target_link_libraries (libzmq ${OPTIONAL_LIBRARIES})
     set_target_properties (libzmq PROPERTIES
       PUBLIC_HEADER "${public_headers}"
@@ -769,7 +768,7 @@ if (MSVC)
   endif()
   
   if (BUILD_STATIC)
-    add_library (libzmq-static STATIC ${sources})
+    add_library (libzmq-static STATIC $<TARGET_OBJECTS:objects> ${CMAKE_CURRENT_BINARY_DIR}/version.rc)
     set_target_properties (libzmq-static PROPERTIES
       PUBLIC_HEADER "${public_headers}"
       RELEASE_POSTFIX "${MSVC_TOOLSET}-mt-s-${ZMQ_VERSION_MAJOR}_${ZMQ_VERSION_MINOR}_${ZMQ_VERSION_PATCH}"
@@ -780,7 +779,7 @@ if (MSVC)
   endif()
 else ()
   if (BUILD_SHARED)
-    add_library (libzmq SHARED ${sources} ${public_headers} ${html-docs} ${readme-docs} ${zmq-pkgconfig})
+    add_library (libzmq SHARED $<TARGET_OBJECTS:objects> ${public_headers} ${html-docs} ${readme-docs} ${zmq-pkgconfig} ${CMAKE_CURRENT_BINARY_DIR}/version.rc)
     target_link_libraries (libzmq ${OPTIONAL_LIBRARIES})
     # NOTE: the SOVERSION MUST be the same as the one generated by libtool!
     set_target_properties (libzmq PROPERTIES
@@ -806,7 +805,7 @@ else ()
   endif()
 
   if (BUILD_STATIC)
-    add_library (libzmq-static STATIC ${sources} ${public_headers} ${html-docs} ${readme-docs} ${zmq-pkgconfig})
+    add_library (libzmq-static STATIC $<TARGET_OBJECTS:objects> ${public_headers} ${html-docs} ${readme-docs} ${zmq-pkgconfig} ${CMAKE_CURRENT_BINARY_DIR}/version.rc)
     set_target_properties (libzmq-static PROPERTIES
       PUBLIC_HEADER "${public_headers}"
       COMPILE_DEFINITIONS "ZMQ_STATIC"
@@ -815,7 +814,7 @@ else ()
   endif()
 endif ()
 
-foreach (target ${target_outputs})
+foreach (target ${target_outputs} objects)
   target_include_directories (${target}
     PUBLIC
       $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/include>

tests/CMakeLists.txt

@@ -145,8 +145,12 @@ if(WIN32)
 endif()
 
 # add library and include dirs for all targets
-link_libraries(libzmq ${OPTIONAL_LIBRARIES})
-include_directories("${CMAKE_SOURCE_DIR}/../include")
+if (BUILD_SHARED)
+link_libraries(libzmq ${OPTIONAL_LIBRARIES} ${CMAKE_THREAD_LIBS_INIT})
+else ()
+link_libraries(libzmq-static ${OPTIONAL_LIBRARIES} ${CMAKE_THREAD_LIBS_INIT})
+endif ()
+include_directories("${CMAKE_SOURCE_DIR}/../include" "${CMAKE_BINARY_DIR}")
 
 foreach(test ${tests})
   # target_sources not supported before CMake 3.1