diff --git a/clang/lib/Sema/SemaCast.cpp b/clang/lib/Sema/SemaCast.cpp
--- a/clang/lib/Sema/SemaCast.cpp
+++ b/clang/lib/Sema/SemaCast.cpp
@@ -2204,13 +2204,19 @@
     // C++ 5.2.10p4: A pointer can be explicitly converted to any integral
     //   type large enough to hold it; except in Microsoft mode, where the
     //   integral type size doesn't matter (except we don't allow bool).
-    bool MicrosoftException = Self.getLangOpts().MicrosoftExt &&
-                              !DestType->isBooleanType();
     if ((Self.Context.getTypeSize(SrcType) >
-         Self.Context.getTypeSize(DestType)) &&
-         !MicrosoftException) {
-      msg = diag::err_bad_reinterpret_cast_small_int;
-      return TC_Failed;
+         Self.Context.getTypeSize(DestType))) {
+      bool MicrosoftException =
+          Self.getLangOpts().MicrosoftExt && !DestType->isBooleanType();
+      if (MicrosoftException) {
+        unsigned Diag = SrcType->isVoidPointerType()
+                            ? diag::warn_void_pointer_to_int_cast
+                            : diag::warn_pointer_to_int_cast;
+        Self.Diag(OpRange.getBegin(), Diag) << SrcType << DestType << OpRange;
+      } else {
+        msg = diag::err_bad_reinterpret_cast_small_int;
+        return TC_Failed;
+      }
     }
     Kind = CK_PointerToIntegral;
     return TC_Success;
diff --git a/clang/test/SemaCXX/MicrosoftExtensions.cpp b/clang/test/SemaCXX/MicrosoftExtensions.cpp
--- a/clang/test/SemaCXX/MicrosoftExtensions.cpp
+++ b/clang/test/SemaCXX/MicrosoftExtensions.cpp
@@ -200,10 +200,24 @@
 static const int static_var = 3; // expected-warning {{redeclaring non-static 'static_var' as static is a Microsoft extension}}
 
 void pointer_to_integral_type_conv(char* ptr) {
-   char ch = (char)ptr;
-   short sh = (short)ptr;
-   ch = (char)ptr;
-   sh = (short)ptr;
+   char ch = (char)ptr; // expected-warning {{cast to smaller integer type 'char' from 'char *'}}
+   short sh = (short)ptr; // expected-warning {{cast to smaller integer type 'short' from 'char *'}}
+   ch = (char)ptr; // expected-warning {{cast to smaller integer type 'char' from 'char *'}}
+   sh = (short)ptr; // expected-warning {{cast to smaller integer type 'short' from 'char *'}}
+
+   // These are valid C++.
+   bool b = (bool)ptr;
+   b = static_cast<bool>(ptr);
+
+   // This is bad.
+   b = reinterpret_cast<bool>(ptr); // expected-error {{cast from pointer to smaller type 'bool' loses information}}
+}
+
+void void_pointer_to_integral_type_conv(void* ptr) {
+   char ch = (char)ptr; // expected-warning {{cast to smaller integer type 'char' from 'void *'}}
+   short sh = (short)ptr; // expected-warning {{cast to smaller integer type 'short' from 'void *'}}
+   ch = (char)ptr; // expected-warning {{cast to smaller integer type 'char' from 'void *'}}
+   sh = (short)ptr; // expected-warning {{cast to smaller integer type 'short' from 'void *'}}
 
    // These are valid C++.
    bool b = (bool)ptr;