This should show value of _MSC_VER when build fails with new version of MSVC.

Note, it is not documented so far for newly released  MSVC 17.1.

Author: hvlad

src/common/os/win32/mod_loader.cpp

@@ -87,26 +87,34 @@ class ContextActivator
 		memset(&ackd, 0, sizeof(ackd));
 		ackd.cbSize = sizeof(ackd);
 
-		// if CRT already present in some activation context then nothing to do
-		if ((*mFindActCtxSectionString)
-				(0, NULL,
-				ACTIVATION_CONTEXT_SECTION_DLL_REDIRECTION,
+		const char* crtDll =
 #if _MSC_VER == 1400
-                    "msvcr80.dll",
+			"msvcr80.dll";
 #elif _MSC_VER == 1500
-                    "msvcr90.dll",
+			"msvcr90.dll";
 #elif _MSC_VER == 1600
-				"msvcr100.dll",
+			"msvcr100.dll";
 #elif _MSC_VER == 1700
-				"msvcr110.dll",
+			"msvcr110.dll";
 #elif _MSC_VER == 1800
-					"msvcr120.dll",
+			"msvcr120.dll";
 #elif _MSC_VER >= 1900 && _MSC_VER <= 1930
-					"vcruntime140.dll",
+			"vcruntime140.dll";
 #else
-                    #error Specify CRT DLL name here !
+			"";
+
+#define TO_STR(x) #x
+#define ERRSTR(x) "Unknown " #x " value: "  TO_STR(x) ". Specify CRT DLL name here !"
+
+		static_assert(false, ERRSTR(_MSC_VER));
+//		#error Specify CRT DLL name here !
 #endif
-				&ackd))
+
+		// if CRT already present in some activation context then nothing to do
+		if ((*mFindActCtxSectionString)
+				(0, NULL,
+				ACTIVATION_CONTEXT_SECTION_DLL_REDIRECTION,
+				crtDll, &ackd))
 		{
 			return;
 		}