cleanup: require CMake >= 3.15 with MSVC (#6190)

coryan · web-flow · commit 19ff12399c2f · 2021-04-05T13:34:17.000Z
diff --git a/CMakeLists.txt b/CMakeLists.txt
@@ -45,9 +45,6 @@ if (NOT ("${GOOGLE_CLOUD_CPP_CXX_STANDARD}" STREQUAL ""))
             "GOOGLE_CLOUD_CPP_CXX_STANDARD is retired, use CMAKE_CXX_STANDARD")
 endif ()
 
-list(APPEND CMAKE_MODULE_PATH ${PROJECT_SOURCE_DIR}/cmake)
-include(SelectMSVCRuntime)
-
 if ("${CMAKE_CXX_COMPILER_ID}" STREQUAL "GNU")
 
     # gcc-4.8 is the first release that claims C++11 support.
@@ -68,8 +65,20 @@ elseif ("${CMAKE_CXX_COMPILER_ID}" STREQUAL "Clang")
                 " either lack C++11 support or have bugs that prevent us from"
                 " using them.")
     endif ()
+elseif ("${CMAKE_CXX_COMPILER_ID}" STREQUAL "MSVC")
+
+    if (CMAKE_VERSION VERSION_LESS 3.15)
+        message(
+            FATAL_ERROR
+                "MSVC builds require CMake >= 3.15."
+                " Previous versions of CMake lack a standard mechanism to"
+                " select the runtime C++ library.")
+    endif ()
 endif ()
 
+list(APPEND CMAKE_MODULE_PATH ${PROJECT_SOURCE_DIR}/cmake)
+include(SelectMSVCRuntime)
+
 option(GOOGLE_CLOUD_CPP_ENABLE_MACOS_OPENSSL_CHECK
        "If enabled, check that the user has defined OPENSSL_ROOT_DIR on macOS"
        ON)
diff --git a/cmake/SelectMSVCRuntime.cmake b/cmake/SelectMSVCRuntime.cmake
@@ -29,30 +29,10 @@
 #
 
 if (MSVC)
-    # TODO(#5852) - if we require CMake >= 3.15 we can remove this conditional
-    # and the hacks below.
-    if (NOT (CMAKE_VERSION VERSION_LESS 3.15))
-        if (VCPKG_TARGET_TRIPLET MATCHES "-static$")
-            set(CMAKE_MSVC_RUNTIME_LIBRARY
-                "MultiThreaded$<$<CONFIG:Debug>:Debug>")
-        else ()
-            set(CMAKE_MSVC_RUNTIME_LIBRARY
-                "MultiThreaded$<$<CONFIG:Debug>:Debug>DLL")
-        endif ()
-    elseif (VCPKG_TARGET_TRIPLET MATCHES "-static$")
-        message(
-            WARNING
-                [===[
-CMake is too old to use CMAKE_MSVC_RUNTIME_LIBRARY.
-Attempting to set CMAKE_CXX_FLAGS* to get consistent CRT versions.
-]===])
-        foreach (flag_var
-                 CMAKE_CXX_FLAGS CMAKE_CXX_FLAGS_DEBUG CMAKE_CXX_FLAGS_RELEASE
-                 CMAKE_CXX_FLAGS_MINSIZEREL CMAKE_CXX_FLAGS_RELWITHDEBINFO)
-            if (${flag_var} MATCHES "/MD")
-                string(REGEX REPLACE "/MD" "/MT" ${flag_var} "${${flag_var}}")
-            endif ()
-        endforeach (flag_var)
-        unset(flag_var)
+    if (VCPKG_TARGET_TRIPLET MATCHES "-static$")
+        set(CMAKE_MSVC_RUNTIME_LIBRARY "MultiThreaded$<$<CONFIG:Debug>:Debug>")
+    else ()
+        set(CMAKE_MSVC_RUNTIME_LIBRARY
+            "MultiThreaded$<$<CONFIG:Debug>:Debug>DLL")
     endif ()
 endif ()
