Commit 06815bf8 authored by Tom Stellard's avatar Tom Stellard
Browse files

Merging r326476: 

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r326476 | mstorsjo | 2018-03-01 12:22:57 -0800 (Thu, 01 Mar 2018) | 7 lines

[RecordLayout] Only assert that fundamental type sizes are power of two on MSVC

Make types with sizes that aren't a power of two an error (that can
be disabled) in structs with ms_struct layout, except on mingw where
the situation is quite likely to occur and GCC handles it silently.

Differential Revision: https://reviews.llvm.org/D43908
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llvm-svn: 333571
parent ba3c53d0

clang/include/clang/Basic/DiagnosticSemaKinds.td

+4 −0
Original line number Diff line number Diff line
@@ -759,6 +759,10 @@ def warn_cxx_ms_struct : 
  Warning<"ms_struct may not produce Microsoft-compatible layouts for classes "

          "with base classes or virtual functions">,

  DefaultError, InGroup<IncompatibleMSStruct>;

def warn_npot_ms_struct :

  Warning<"ms_struct may not produce Microsoft-compatible layouts with fundamental "

          "data types with sizes that aren't a power of two">,

  DefaultError, InGroup<IncompatibleMSStruct>;

def err_section_conflict : Error<"%0 causes a section type conflict with %1">;

def err_no_base_classes : Error<"invalid use of '__super', %0 has no base classes">;

def err_invalid_super_scope : Error<"invalid use of '__super', "

clang/lib/AST/RecordLayoutBuilder.cpp

+26 −4
Original line number Diff line number Diff line
@@ -1751,10 +1751,32 @@ void ItaniumRecordLayoutBuilder::LayoutField(const FieldDecl *D, 
      QualType T = Context.getBaseElementType(D->getType());

      if (const BuiltinType *BTy = T->getAs<BuiltinType>()) {

        CharUnits TypeSize = Context.getTypeSizeInChars(BTy);



        if (!llvm::isPowerOf2_64(TypeSize.getQuantity())) {

          assert(

            (llvm::isPowerOf2_64(TypeSize.getQuantity()) ||

             Context.getTargetInfo().getTriple().isWindowsGNUEnvironment()) &&

            "Non PowerOf2 size outside of GNU mode");

              !Context.getTargetInfo().getTriple().isWindowsMSVCEnvironment() &&

              "Non PowerOf2 size in MSVC mode");

          // Base types with sizes that aren't a power of two don't work

          // with the layout rules for MS structs. This isn't an issue in

          // MSVC itself since there are no such base data types there.

          // On e.g. x86_32 mingw and linux, long double is 12 bytes though.

          // Any structs involving that data type obviously can't be ABI

          // compatible with MSVC regardless of how it is laid out.



          // Since ms_struct can be mass enabled (via a pragma or via the

          // -mms-bitfields command line parameter), this can trigger for

          // structs that don't actually need MSVC compatibility, so we

          // need to be able to sidestep the ms_struct layout for these types.



          // Since the combination of -mms-bitfields together with structs

          // like max_align_t (which contains a long double) for mingw is

          // quite comon (and GCC handles it silently), just handle it

          // silently there. For other targets that have ms_struct enabled

          // (most probably via a pragma or attribute), trigger a diagnostic

          // that defaults to an error.

          if (!Context.getTargetInfo().getTriple().isWindowsGNUEnvironment())

            Diag(D->getLocation(), diag::warn_npot_ms_struct);

        }

        if (TypeSize > FieldAlign &&

            llvm::isPowerOf2_64(TypeSize.getQuantity()))

          FieldAlign = TypeSize;

clang/test/CodeGen/ms_struct-long-double.c

0 → 100644
+17 −0
Original line number Diff line number Diff line 
// RUN: %clang_cc1 -emit-llvm-only -triple i686-windows-gnu -fdump-record-layouts %s | FileCheck %s

// RUN: %clang_cc1 -emit-llvm-only -triple i686-linux -fdump-record-layouts -Wno-incompatible-ms-struct %s | FileCheck %s

// RUN: not %clang_cc1 -emit-llvm-only -triple i686-linux -fdump-record-layouts %s 2>&1 | FileCheck %s -check-prefix=ERROR



struct ldb_struct {

  char c;

  long double ldb;

} __attribute__((__ms_struct__));



struct ldb_struct a;



// CHECK:             0 | struct ldb_struct

// CHECK-NEXT:        0 |   char c

// CHECK-NEXT:        4 |   long double ldb

// CHECK-NEXT:          | [sizeof=16, align=4]



// ERROR: error: ms_struct may not produce Microsoft-compatible layouts with fundamental data types with sizes that aren't a power of two