Merge topic 'vs-lang-C'

5c04e77e07 VS: Restore compilation of '.C' sources as C++

Acked-by: Kitware Robot <kwrobot@kitware.com>
Merge-request: !4880

Tests/CxxOnly/CMakeLists.txt

@@ -5,7 +5,7 @@ set(CMAKE_DEBUG_POSTFIX "_test_debug_postfix")
 if(WIN32)
   set(EXTRA_SRCS test.CPP)
 endif()
-add_library(testcxx1.my STATIC libcxx1.cxx ${EXTRA_SRCS})
+add_library(testcxx1.my STATIC libcxx1.cxx test.C ${EXTRA_SRCS})
 add_library(testcxx2 SHARED libcxx2.cxx)
 add_executable (CxxOnly cxxonly.cxx)
 target_link_libraries(CxxOnly testcxx1.my testcxx2)

Tests/CxxOnly/cxxonly.cxx

@@ -1,5 +1,6 @@
 #include "libcxx1.h"
 #include "libcxx2.h"
+extern int testC;
 #ifdef _MSC_VER
 extern int testCPP;
 #endif
@@ -8,6 +9,7 @@ extern int testCPP;
 
 int main()
 {
+  testC = 1;
 #ifdef _MSC_VER
   testCPP = 1;
 #endif

Tests/CxxOnly/test.C

@@ -0,0 +1 @@
+int testC;