Merge 0b656495436f57212be8700794a3d5fb14000c5f into 1b96fa13f549387b7549cc89e1a785cf143a1a50

With CMake 3.15, a new mechanism was added to control which CRT
libraries link to. Because the minimum CMake version is above 3.15,
googletest can leverage it in the implementation of
gtest_force_shared_crt.

If CMAKE_MSVC_RUNTIME_LIBRARY is already defined, googletest will
respect its value rather than replace it, allowing for users to
customize the exact CRT used by googletest.

googletest/CMakeLists.txt

@@ -8,10 +8,12 @@
 # ctest. You can select which tests to run using 'ctest -R regex'.
 # For more options, run 'ctest --help'.
 
-if (DEFINED gtest_force_shared_crt)
-  message(DEPRECATION
-    "gtest_force_shared_crt is deprecated and ignored. Use `CMAKE_MSVC_RUNTIME_LIBRARY` to configure the MSVC runtime library")
-endif()
+# When other libraries are using a shared version of runtime libraries,
+# Google Test also has to use one.
+option(
+  gtest_force_shared_crt
+  "Use shared (DLL) run-time lib even when Google Test is built as static lib."
+  OFF)
 
 option(gtest_build_tests "Build all of gtest's own tests." OFF)
 

googletest/README.md

@@ -117,16 +117,10 @@ something like the following: gtest.lib(gtest-all.obj) : error LNK2038: mismatch
 detected for 'RuntimeLibrary': value 'MTd_StaticDebug' doesn't match value
 'MDd_DynamicDebug' in main.obj
 
-This is resolved by forcing googletest to dynamically link to the C runtimes.
-CMake 3.15 added the variable `CMAKE_MSVC_RUNTIME_LIBRARY` as the way to
-select the C runtime used by projects.
-
-To do this, either add
-`set(CMAKE_MSVC_RUNTIME_LIBRARY "MultiThreaded$<$<CONFIG:Debug>:Debug>DLL")`
-to the project's CMakeLists.txt before including googletest, or set it
-on the command line with
-`-DCMAKE_MSVC_RUNTIME_LIBRARY="MultiThreaded$<$<CONFIG:Debug>:Debug>DLL"`.
+GoogleTest already has a CMake option for this: `gtest_force_shared_crt`
 
+Enabling this option will make gtest link the runtimes dynamically too, and
+match the project in which it is included.
 
 #### C++ Standard Version
 

googletest/cmake/internal_utils.cmake

@@ -62,19 +62,18 @@ macro(config_compiler_and_linker)
 
   fix_default_compiler_settings_()
 
-  # When Google Test is built as a shared library, it should also use
-  # shared runtime libraries. Otherwise, it may end up with multiple
-  # copies of runtime library data in different modules, resulting in
-  # hard-to-find crashes. When it is built as a static library, it is
-  # preferable to use CRT as static libraries, as we don't have to rely
-  # on CRT DLLs being available. CMake defaults to using shared
-  # CRT libraries, so we change that here.
-  if (NOT BUILD_SHARED_LIBS AND NOT DEFINED CMAKE_MSVC_RUNTIME_LIBRARY)
-    set(CMAKE_MSVC_RUNTIME_LIBRARY "MultiThreaded$<$<CONFIG:Debug>:Debug>")
-  endif()
-
-
   if (MSVC)
+    # When Google Test is built as a shared library, it should also use
+    # shared runtime libraries. Otherwise, it may end up with multiple
+    # copies of runtime library data in different modules, resulting in
+    # hard-to-find crashes. When it is built as a static library, it is
+    # preferable to use CRT as static libraries, as we don't have to rely
+    # on CRT DLLs being available. CMake defaults to using shared
+    # CRT libraries, so we change that here.
+    if (NOT BUILD_SHARED_LIBS AND NOT gtest_force_shared_crt AND NOT DEFINED CMAKE_MSVC_RUNTIME_LIBRARY)
+      set(CMAKE_MSVC_RUNTIME_LIBRARY "MultiThreaded$<$<CONFIG:Debug>:Debug>")
+    endif()
+
     # Newlines inside flags variables break CMake's NMake generator.
     # TODO(vladl@google.com): Add -RTCs and -RTCu to debug builds.
     set(cxx_base_flags "-GS -W4 -WX -wd4251 -wd4275 -nologo -J")