Consider "_BitInt(5) : 6" to be oversized; add tests for bit-fields

Author: MitalAshok

clang/lib/AST/RecordLayoutBuilder.cpp

@@ -2433,9 +2433,17 @@ DiagnosticBuilder ItaniumRecordLayoutBuilder::Diag(SourceLocation Loc,
 /// This function does not check if the type is POD first
 static bool isItaniumPOD(const ASTContext &Context, const CXXRecordDecl *RD) {
   const auto IsDisqualifying = [&](const FieldDecl *FD) -> bool {
-    if (FD->isBitField())
-      if (FD->getBitWidthValue(Context) > Context.getTypeSize(FD->getType()))
+    if (FD->isBitField()) {
+      QualType DeclaredType = FD->getType();
+      unsigned DeclaredWidth;
+      if (const BitIntType *BIT = DeclaredType->getAs<BitIntType>())
+        DeclaredWidth = BIT->getNumBits();
+      else
+        DeclaredWidth = Context.getTypeSize(FD->getType());
+
+      if (FD->getBitWidthValue(Context) > DeclaredWidth)
         return true;
+    }
 
     return FD->isPotentiallyOverlapping();
   };

clang/test/Layout/itanium-padded-bit-field.cpp

@@ -0,0 +1,106 @@
+// RUN: %clang_cc1 -DOLD_ABI=false -std=c++17 -fsyntax-only -triple %itanium_abi_triple -fdump-record-layouts -Wno-bitfield-width %s | FileCheck %s --check-prefixes=CHECK,NEW
+// RUN: %clang_cc1 -fclang-abi-compat=19.0 -DOLD_ABI=true -std=c++17 -fsyntax-only -triple %itanium_abi_triple -fdump-record-layouts -Wno-bitfield-width %s | FileCheck %s --check-prefixes=CHECK,OLD
+
+using i4 = __INT32_TYPE__;
+using i1 = __INT8_TYPE__;
+
+struct OversizedBase {
+  i4 i : 33;
+};
+
+static_assert(sizeof(OversizedBase) == 8);
+// CHECK:*** Dumping AST Record Layout
+// CHECK:           0 | struct OversizedBase
+// CHECK-NEXT: 0:0-32 |   i4 i
+
+// NEW-NEXT:          | [sizeof=8, dsize=5, align=4,
+// NEW-NEXT:          |  nvsize=5, nvalign=4]
+
+// OLD-NEXT:          | [sizeof=8, dsize=8, align=4,
+// OLD-NEXT:          |  nvsize=8, nvalign=4]
+
+struct X : OversizedBase {
+  i1 in_padding;
+};
+static_assert(sizeof(X) == (OLD_ABI ? 12 : 8));
+// CHECK:*** Dumping AST Record Layout
+// CHECK:           0 | struct X
+// CHECK-NEXT:      0 |   struct OversizedBase (base)
+// CHECK-NEXT: 0:0-32 |     i4 i
+
+// NEW-NEXT:        5 |   i1 in_padding
+// NEW-NEXT:          | [sizeof=8, dsize=6, align=4,
+// NEW-NEXT:          |  nvsize=6, nvalign=4]
+
+// OLD-NEXT:        8 |   i1 in_padding
+// OLD-NEXT:          | [sizeof=12, dsize=9, align=4,
+// OLD-NEXT:          |  nvsize=9, nvalign=4]
+
+struct Y : OversizedBase {
+  i1 in_padding[3];
+};
+
+static_assert(sizeof(Y) == (OLD_ABI ? 12 : 8));
+// CHECK:*** Dumping AST Record Layout
+// CHECK:           0 | struct Y
+// CHECK-NEXT:      0 |   struct OversizedBase (base)
+// CHECK-NEXT: 0:0-32 |     i4 i
+
+// NEW-NEXT:        5 |   i1[3] in_padding
+// NEW-NEXT:          | [sizeof=8, dsize=8, align=4,
+// NEW-NEXT:          |  nvsize=8, nvalign=4]
+
+// OLD-NEXT:        8 |   i1[3] in_padding
+// OLD-NEXT:          | [sizeof=12, dsize=11, align=4,
+// OLD-NEXT:          |  nvsize=11, nvalign=4]
+
+struct Z : OversizedBase {
+  i1 in_padding[4];
+};
+
+static_assert(sizeof(Z) == 12);
+// CHECK:*** Dumping AST Record Layout
+// CHECK:           0 | struct Z
+// CHECK-NEXT:      0 |   struct OversizedBase (base)
+// CHECK-NEXT: 0:0-32 |     i4 i
+
+// NEW-NEXT:        5 |   i1[4] in_padding
+// NEW-NEXT:          | [sizeof=12, dsize=9, align=4,
+// NEW-NEXT:          |  nvsize=9, nvalign=4]
+
+// OLD-NEXT:        8 |   i1[4] in_padding
+// OLD-NEXT:          | [sizeof=12, dsize=12, align=4,
+// OLD-NEXT:          |  nvsize=12, nvalign=4]
+
+namespace BitInt {
+struct alignas(4) OversizedBase {
+  _BitInt(9) i : 10;
+};
+static_assert(sizeof(OversizedBase) == 4);
+// CHECK:*** Dumping AST Record Layout
+// CHECK:           0 | struct BitInt::OversizedBase
+// CHECK-NEXT: 0:0-9  |   _BitInt(9) i
+
+// NEW-NEXT:        | [sizeof=4, dsize=2, align=4,
+// NEW-NEXT:        |  nvsize=2, nvalign=4]
+
+// OLD-NEXT:        | [sizeof=4, dsize=4, align=4,
+// OLD-NEXT:        |  nvsize=4, nvalign=4]
+
+struct X : OversizedBase {
+  i1 in_padding;
+};
+static_assert(sizeof(X) == (OLD_ABI ? 8 : 4));
+// CHECK:*** Dumping AST Record Layout
+// CHECK:           0 | struct BitInt::X
+// CHECK-NEXT:      0 |   struct BitInt::OversizedBase (base)
+// CHECK-NEXT:  0:0-9 |     _BitInt(9) i
+
+// NEW-NEXT:        2 |   i1 in_padding
+// NEW-NEXT:          | [sizeof=4, dsize=3, align=4,
+// NEW-NEXT:          |  nvsize=3, nvalign=4]
+
+// OLD-NEXT:        4 |   i1 in_padding
+// OLD-NEXT:          | [sizeof=8, dsize=5, align=4,
+// OLD-NEXT:          |  nvsize=5, nvalign=4]
+}

clang/test/Layout/no-unique-address.cpp

@@ -1,5 +1,5 @@
-// RUN: %clang_cc1 -std=c++2a -fsyntax-only -triple x86_64-linux-gnu -fdump-record-layouts %s | FileCheck %s --check-prefix=NEW --check-prefix=CHECK
-// RUN: %clang_cc1 -fclang-abi-compat=19.0 -DOLD_ABI=1 -std=c++2a -fsyntax-only -triple x86_64-linux-gnu -fdump-record-layouts %s | FileCheck %s --check-prefix=OLD --check-prefix=CHECK
+// RUN: %clang_cc1 -std=c++20 -fsyntax-only -triple x86_64-linux-gnu -fdump-record-layouts %s | FileCheck %s --check-prefixes=CHECK,NEW
+// RUN: %clang_cc1 -fclang-abi-compat=19.0 -std=c++20 -fsyntax-only -triple x86_64-linux-gnu -fdump-record-layouts %s | FileCheck %s --check-prefixes=CHECK,OLD
 
 namespace Empty {
   struct A {};