Made it so that a dummy .cpp is actually created when compiling with VC++.

cmake/OpenCVModule.cmake

@@ -470,8 +470,16 @@ endmacro()
 #   ocv_create_module(<extra link dependencies>)
 #   ocv_create_module(SKIP_LINK)
 macro(ocv_create_module)
+  # The condition we ought to be testing here is whether ocv_add_precompiled_headers will
+  # be called at some point in the future. We can't look into the future, though,
+  # so this will have to do.
+  if(EXISTS "${CMAKE_CURRENT_SOURCE_DIR}/src/precomp.hpp")
+    get_native_precompiled_header(${the_module} precomp.hpp)
+  endif()
+
   add_library(${the_module} ${OPENCV_MODULE_TYPE} ${OPENCV_MODULE_${the_module}_HEADERS} ${OPENCV_MODULE_${the_module}_SOURCES}
-    "${OPENCV_CONFIG_FILE_INCLUDE_DIR}/cvconfig.h" "${OPENCV_CONFIG_FILE_INCLUDE_DIR}/opencv2/opencv_modules.hpp")
+    "${OPENCV_CONFIG_FILE_INCLUDE_DIR}/cvconfig.h" "${OPENCV_CONFIG_FILE_INCLUDE_DIR}/opencv2/opencv_modules.hpp"
+    ${${the_module}_pch})
 
   if(NOT "${ARGN}" STREQUAL "SKIP_LINK")
     target_link_libraries(${the_module} ${OPENCV_MODULE_${the_module}_DEPS} ${OPENCV_MODULE_${the_module}_DEPS_EXT} ${OPENCV_LINKER_LIBS} ${IPP_LIBS} ${ARGN})
@@ -637,7 +645,9 @@ function(ocv_add_perf_tests)
         set(OPENCV_PERF_${the_module}_SOURCES ${perf_srcs} ${perf_hdrs})
       endif()
 
-      add_executable(${the_target} ${OPENCV_PERF_${the_module}_SOURCES})
+      get_native_precompiled_header(${the_target} test_precomp.hpp)
+
+      add_executable(${the_target} ${OPENCV_PERF_${the_module}_SOURCES} ${${the_target}_pch})
       target_link_libraries(${the_target} ${OPENCV_MODULE_${the_module}_DEPS} ${perf_deps} ${OPENCV_LINKER_LIBS})
       add_dependencies(opencv_perf_tests ${the_target})
 
@@ -685,7 +695,9 @@ function(ocv_add_accuracy_tests)
         set(OPENCV_TEST_${the_module}_SOURCES ${test_srcs} ${test_hdrs})
       endif()
 
-      add_executable(${the_target} ${OPENCV_TEST_${the_module}_SOURCES})
+      get_native_precompiled_header(${the_target} test_precomp.hpp)
+
+      add_executable(${the_target} ${OPENCV_TEST_${the_module}_SOURCES} ${${the_target}_pch})
       target_link_libraries(${the_target} ${OPENCV_MODULE_${the_module}_DEPS} ${test_deps} ${OPENCV_LINKER_LIBS})
       add_dependencies(opencv_tests ${the_target})
 

cmake/OpenCVPCHSupport.cmake

@@ -272,12 +272,9 @@ ENDMACRO(ADD_PRECOMPILED_HEADER)
 MACRO(GET_NATIVE_PRECOMPILED_HEADER _targetName _input)
 
     if(CMAKE_GENERATOR MATCHES "^Visual.*$")
-        SET(_dummy_str "#include \"${_input}\"\n"
-"// This is required to suppress LNK4221.  Very annoying.\n"
-"void *g_${_targetName}Dummy = 0\;\n")
+        set(_dummy_str "#include \"${_input}\"\n")
 
-        # Use of cxx extension for generated files (as Qt does)
-        SET(${_targetName}_pch ${CMAKE_CURRENT_BINARY_DIR}/${_targetName}_pch.cxx)
+        set(${_targetName}_pch ${CMAKE_CURRENT_BINARY_DIR}/${_targetName}_pch.cpp)
         if(EXISTS ${${_targetName}_pch})
             # Check if contents is the same, if not rewrite
             # todo
@@ -337,11 +334,7 @@ ENDMACRO(ADD_NATIVE_PRECOMPILED_HEADER)
 
 macro(ocv_add_precompiled_header_to_target the_target pch_header)
   if(PCHSupport_FOUND AND ENABLE_PRECOMPILED_HEADERS AND EXISTS "${pch_header}")
-    if(CMAKE_GENERATOR MATCHES Visual)
-      string(REGEX REPLACE "hpp$" "cpp" ${the_target}_pch "${pch_header}")
-      add_native_precompiled_header(${the_target} ${pch_header})
-      unset(${the_target}_pch)
-    elseif(CMAKE_GENERATOR MATCHES Xcode)
+    if(CMAKE_GENERATOR MATCHES "^Visual" OR CMAKE_GENERATOR MATCHES Xcode)
       add_native_precompiled_header(${the_target} ${pch_header})
     elseif(CMAKE_COMPILER_IS_GNUCXX AND CMAKE_GENERATOR MATCHES "Makefiles|Ninja")
       add_precompiled_header(${the_target} ${pch_header})