[Sema] Don't emit pointer to int cast warnings under -Wmicrosoft-cast

[aeubanks]

Summary

MSVC also warns on this:
$ cat /tmp/a.c
int f(void* p) { return (int) p; }

$ cl /c /tmp/a.c
C:/src/tmp/a.c(1): warning C4311: 'type cast': pointer truncation from
'void *' to 'int'

Warnings originally added in https://reviews.llvm.org/D72231.

[rnk]

Looking at the review, I think @rsmith requested this -Wmicrosoft-cast behavior here:
https://reviews.llvm.org/D72231#1857660

This change looks good to me, but I wanted to get his input before we undo his request.

[rnk]

I re-read Richard's comment:

Would it make sense to put the MS extension warning into the -Wpointer-to-int-cast group so that we can control this warning consistently across platforms? You could get that effect by introducing a new warning group (eg, "-Wmicrosoft-pointer-to-int-cast") containing just the ExtWarn warning, and putting that group in both MicrosoftCast and PointerToIntCast.

My interpretation is that he was suggesting the change that you are making here. So, let's continue without his additional approval.

I'll go ahead and push this in a minute.

[rnk]

I think I patched this in, ran tests, but didn't push. Feel free to push if you get the chance.

clang/include/clang/Basic/DiagnosticSemaKinds.td

def warn_pointer_to_enum_cast : Warning<
   warn_pointer_to_int_cast.Text>,
   InGroup<PointerToEnumCast>;
 def warn_void_pointer_to_int_cast : Warning<
   "cast to smaller integer type %1 from %0">,
   InGroup<VoidPointerToIntCast>;
 def warn_void_pointer_to_enum_cast : Warning<
   warn_void_pointer_to_int_cast.Text>,
   InGroup<VoidPointerToEnumCast>;
-def ext_ms_pointer_to_int_cast : ExtWarn<
-  "cast to smaller integer type %1 from %0 is a Microsoft extension">,
-InGroup<MicrosoftCast>;
 
 def warn_attribute_ignored_for_field_of_type : Warning<
   "%0 attribute ignored for field of type %1">,
   InGroup<IgnoredAttributes>;
 def warn_no_underlying_type_specified_for_enum_bitfield : Warning<
   "enums in the Microsoft ABI are signed integers by default; consider giving "
   "the enum %0 an unsigned underlying type to make this code portable">,
   InGroup<SignedEnumBitfield>, DefaultIgnore;

clang/lib/Sema/SemaCast.cpp

if ((Self.Context.getTypeSize(SrcType) >
          Self.Context.getTypeSize(DestType)) &&
         !DestType->isBooleanType()) {
       // C 6.3.2.3p6: Any pointer type may be converted to an integer type.
       // Except as previously specified, the result is implementation-defined.
       // If the result cannot be represented in the integer type, the behavior
       // is undefined. The result need not be in the range of values of any
       // integer type.
       unsigned Diag;
-      if (Self.getLangOpts().MicrosoftExt)
-        Diag = diag::ext_ms_pointer_to_int_cast;
-      else if (SrcType->isVoidPointerType())
+      if (SrcType->isVoidPointerType())
         Diag = DestType->isEnumeralType() ? diag::warn_void_pointer_to_enum_cast
                                           : diag::warn_void_pointer_to_int_cast;
       else if (DestType->isEnumeralType())
         Diag = diag::warn_pointer_to_enum_cast;
       else
         Diag = diag::warn_pointer_to_int_cast;
       Self.Diag(OpRange.getBegin(), Diag) << SrcType << DestType << OpRange;
     }

clang/test/Sema/MicrosoftExtensions.c

-// RUN: %clang_cc1 -triple i686-windows %s -fsyntax-only -Wno-unused-value -Wmicrosoft -verify -fms-extensions
-
+// RUN: %clang_cc1 -triple i686-windows %s -fsyntax-only -Wno-unused-value -Wno-pointer-to-int-cast -Wmicrosoft -verify -fms-extensions
 
 struct A
 {
    int a[];  /* expected-warning {{flexible array member 'a' in otherwise empty struct is a Microsoft extension}} */
 };
 
 struct PR28407
 {
struct X0 {
   enum E1 : seventeen;
 };
 
 enum : long long {  // expected-warning{{enumeration types with a fixed underlying type are a Microsoft extension}}
   SomeValue = 0x100000000
 };
 
 void pointer_to_integral_type_conv(char* ptr) {
-   char ch = (char)ptr; // expected-warning{{cast to smaller integer type 'char' from 'char *' is a Microsoft extension}}
-   short sh = (short)ptr; // expected-warning{{cast to smaller integer type 'short' from 'char *' is a Microsoft extension}}
-   ch = (char)ptr; // expected-warning{{cast to smaller integer type 'char' from 'char *' is a Microsoft extension}}
-   sh = (short)ptr; // expected-warning{{cast to smaller integer type 'short' from 'char *' is a Microsoft extension}}
+  char ch = (char)ptr;
+  short sh = (short)ptr;
+  ch = (char)ptr;
+  sh = (short)ptr;
 
-   // This is valid ISO C.
-   _Bool b = (_Bool)ptr;
 }
 
 typedef struct {
   UNKNOWN u; // expected-error {{unknown type name 'UNKNOWN'}}
 } AA;
 
 typedef struct {
   AA; // expected-warning {{anonymous structs are a Microsoft extension}}