r251738 - [MSVC Compat] Permit conversions from pointer-to-function to pointer-to-object iff -fms-compatibility

[Nico Weber via cfe-commits]

I think we more commonly say "function pointer":

$ grep 'pointer-to-function' include/clang/Basic/Diagnostic*td | wc -l
       3
$ grep 'function pointer' include/clang/Basic/Diagnostic*td | wc -l
       7

For "object pointer" and "pointer-to-object" it's currently a tie. For
"member pointer" and "pointer-to-member", the former is more common too. We
should probably make all of these consistent – any preferences? "foo
pointer" reads easier to me than "pointer-to-foo", but I'm not a native
speaker.

On Sat, Oct 31, 2015 at 1:42 AM, David Majnemer via cfe-commits <
cfe-commits at lists.llvm.org> wrote:

> Author: majnemer
> Date: Sat Oct 31 03:42:14 2015
> New Revision: 251738
>
> URL: http://llvm.org/viewvc/llvm-project?rev=251738&view=rev
> Log:
> [MSVC Compat] Permit conversions from pointer-to-function to
> pointer-to-object iff -fms-compatibility
>
> We permit implicit conversion from pointer-to-function to
> pointer-to-object when -fms-extensions is specified.  This is rather
> unfortunate, move this into -fms-compatibility and only permit it within
> system headers unless -Wno-error=microsoft-cast is specified.
>
> Modified:
>     cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td
>     cfe/trunk/lib/Sema/SemaOverload.cpp
>     cfe/trunk/test/SemaCXX/MicrosoftCompatibility-cxx98.cpp
>     cfe/trunk/test/SemaCXX/MicrosoftExtensions.cpp
>
> Modified: cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td
> URL:
> http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td?rev=251738&r1=251737&r2=251738&view=diff
>
> ==============================================================================
> --- cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td (original)
> +++ cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td Sat Oct 31
> 03:42:14 2015
> @@ -2635,6 +2635,10 @@ def warn_impcast_null_pointer_to_integer
>  def warn_impcast_floating_point_to_bool : Warning<
>      "implicit conversion turns floating-point number into bool: %0 to
> %1">,
>      InGroup<ImplicitConversionFloatingPointToBool>;
> +def ext_ms_impcast_fn_obj : ExtWarn<
> +  "implicit conversion between pointer-to-function and pointer-to-object
> is a "
> +  "Microsoft extension">,
> +  InGroup<MicrosoftCast>, DefaultError, SFINAEFailure;
>
>  def warn_impcast_pointer_to_bool : Warning<
>      "address of%select{| function| array}0 '%1' will always evaluate to "
>
> Modified: cfe/trunk/lib/Sema/SemaOverload.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaOverload.cpp?rev=251738&r1=251737&r2=251738&view=diff
>
> ==============================================================================
> --- cfe/trunk/lib/Sema/SemaOverload.cpp (original)
> +++ cfe/trunk/lib/Sema/SemaOverload.cpp Sat Oct 31 03:42:14 2015
> @@ -2104,7 +2104,7 @@ bool Sema::IsPointerConversion(Expr *Fro
>    }
>
>    // MSVC allows implicit function to void* type conversion.
> -  if (getLangOpts().MicrosoftExt && FromPointeeType->isFunctionType() &&
> +  if (getLangOpts().MSVCCompat && FromPointeeType->isFunctionType() &&
>        ToPointeeType->isVoidType()) {
>      ConvertedType = BuildSimilarlyQualifiedPointerType(FromTypePtr,
>                                                         ToPointeeType,
> @@ -2666,6 +2666,14 @@ bool Sema::CheckPointerConversion(Expr *
>          // The conversion was successful.
>          Kind = CK_DerivedToBase;
>        }
> +
> +      if (!IsCStyleOrFunctionalCast && FromPointeeType->isFunctionType()
> &&
> +          ToPointeeType->isVoidType()) {
> +        assert(getLangOpts().MSVCCompat &&
> +               "this should only be possible with MSVCCompat!");
> +        Diag(From->getExprLoc(), diag::ext_ms_impcast_fn_obj)
> +            << From->getSourceRange();
> +      }
>      }
>    } else if (const ObjCObjectPointerType *ToPtrType =
>                 ToType->getAs<ObjCObjectPointerType>()) {
>
> Modified: cfe/trunk/test/SemaCXX/MicrosoftCompatibility-cxx98.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/SemaCXX/MicrosoftCompatibility-cxx98.cpp?rev=251738&r1=251737&r2=251738&view=diff
>
> ==============================================================================
> --- cfe/trunk/test/SemaCXX/MicrosoftCompatibility-cxx98.cpp (original)
> +++ cfe/trunk/test/SemaCXX/MicrosoftCompatibility-cxx98.cpp Sat Oct 31
> 03:42:14 2015
> @@ -12,3 +12,12 @@ void (*PR23733_1)() = static_cast<FnPtrT
>  void (*PR23733_2)() = FnPtrTy((void *)0);
>  void (*PR23733_3)() = (FnPtrTy)((void *)0);
>  void (*PR23733_4)() = reinterpret_cast<FnPtrTy>((void *)0);
> +
> +long function_prototype(int a);
> +long (*function_ptr)(int a);
> +
> +void function_to_voidptr_conv() {
> +  void *a1 = function_prototype;  // expected-warning {{implicit
> conversion between pointer-to-function and pointer-to-object is a Microsoft
> extension}}
> +  void *a2 = &function_prototype; // expected-warning {{implicit
> conversion between pointer-to-function and pointer-to-object is a Microsoft
> extension}}
> +  void *a3 = function_ptr;        // expected-warning {{implicit
> conversion between pointer-to-function and pointer-to-object is a Microsoft
> extension}}
> +}
>
> Modified: cfe/trunk/test/SemaCXX/MicrosoftExtensions.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/SemaCXX/MicrosoftExtensions.cpp?rev=251738&r1=251737&r2=251738&view=diff
>
> ==============================================================================
> --- cfe/trunk/test/SemaCXX/MicrosoftExtensions.cpp (original)
> +++ cfe/trunk/test/SemaCXX/MicrosoftExtensions.cpp Sat Oct 31 03:42:14 2015
> @@ -153,16 +153,6 @@ static void static_func() // expected-wa
>  extern const int static_var; // expected-note {{previous declaration is
> here}}
>  static const int static_var = 3; // expected-warning {{redeclaring
> non-static 'static_var' as static is a Microsoft extension}}
>
> -long function_prototype(int a);
> -long (*function_ptr)(int a);
> -
> -void function_to_voidptr_conv() {
> -   void *a1 = function_prototype;
> -   void *a2 = &function_prototype;
> -   void *a3 = function_ptr;
> -}
> -
> -
>  void pointer_to_integral_type_conv(char* ptr) {
>     char ch = (char)ptr;
>     short sh = (short)ptr;
>
>
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