From: Warren Hunt <whunt@google.com>
Date: Fri, 10 Jan 2014 23:32:32 +0000 (+0000)
Subject: [ms-abi] Adjusting Rules for Padding Between Bases
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=d51b71c7b3abd27d82f3f97e09eb1eb1630f7f45;p=clang

[ms-abi] Adjusting Rules for Padding Between Bases

The presence of a VBPtr suppresses the presence of zero sized
sub-objects in the non-virtual portion of the object in the context of
determining if two base objects need alias-avoidance padding placed
between them.

Test cases included.



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@198975 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/AST/RecordLayoutBuilder.cpp b/lib/AST/RecordLayoutBuilder.cpp
index 30293c27c1..6a708a7e8d 100644
--- a/lib/AST/RecordLayoutBuilder.cpp
+++ b/lib/AST/RecordLayoutBuilder.cpp
@@ -2477,6 +2477,9 @@ void MicrosoftRecordLayoutBuilder::injectVBPtr(const CXXRecordDecl *RD) {
          i->second += Offset;
   // Update the object alignment.
   updateAlignment(PointerInfo.Alignment);
+  // The presence of a vbptr suppresses zero sized objects that are not in
+  // virtual bases.
+  HasZeroSizedSubObject = false;
 }
 
 void MicrosoftRecordLayoutBuilder::injectVFPtr(const CXXRecordDecl *RD) {
@@ -2566,6 +2569,9 @@ void MicrosoftRecordLayoutBuilder::injectVPtrs(const CXXRecordDecl *RD) {
     }
   }
   layoutFields(RD);
+  // The presence of a vbptr suppresses zero sized objects that are not in
+  // virtual bases.
+  HasZeroSizedSubObject = false;
 }
 
 void MicrosoftRecordLayoutBuilder::layoutVirtualBases(const CXXRecordDecl *RD) {
diff --git a/test/Layout/ms-x86-alias-avoidance-padding.cpp b/test/Layout/ms-x86-alias-avoidance-padding.cpp
index 1b5d25cd5b..4824913701 100644
--- a/test/Layout/ms-x86-alias-avoidance-padding.cpp
+++ b/test/Layout/ms-x86-alias-avoidance-padding.cpp
@@ -139,29 +139,29 @@ struct BT3 : BT0, BT2 {
 
 struct T0 : AT {
 	T0() {
-		printf("T0 (this) : %d\n", (char*)this - buffer);
+		printf("T0 (this) : %d\n", (int)((char*)this - buffer));
 	}
 };
 
 struct T1 : T0 {
 	char a;
 	T1() {
-		printf("T1 (this) : %d\n", (char*)this - buffer);
-		printf("T1 (fiel) : %d\n", (char*)&a - buffer);
+		printf("T1 (this) : %d\n", (int)((char*)this - buffer));
+		printf("T1 (fiel) : %d\n", (int)((char*)&a - buffer));
 	}
 };
 
 struct T2 : AT {
 	char a;
 	T2() {
-		printf("T2 (this) : %d\n", (char*)this - buffer);
-		printf("T2 (fiel) : %d\n", (char*)&a - buffer);
+		printf("T2 (this) : %d\n", (int)((char*)this - buffer));
+		printf("T2 (fiel) : %d\n", (int)((char*)&a - buffer));
 	}
 };
 
 struct __declspec(align(1)) T3 : virtual T1, virtual T2 {
 	T3() {
-		printf("T3 (this) : %d\n", (char*)this - buffer);
+		printf("T3 (this) : %d\n", (int)((char*)this - buffer));
 	}
 };
 
@@ -196,7 +196,69 @@ struct __declspec(align(1)) T3 : virtual T1, virtual T2 {
 // CHECK-X64-NEXT:      | [sizeof=24, align=8
 // CHECK-X64-NEXT:      |  nvsize=8, nvalign=8]
 
+struct B {};
+struct C { int a; };
+struct D : B, virtual C { B b; };
+struct E : D, B {};
+// CHECK: *** Dumping AST Record Layout
+// CHECK: *** Dumping AST Record Layout
+// CHECK: *** Dumping AST Record Layout
+// CHECK: *** Dumping AST Record Layout
+// CHECK-NEXT:    0 | struct E
+// CHECK-NEXT:    0 |   struct D (base)
+// CHECK-NEXT:    4 |     struct B (base) (empty)
+// CHECK-NEXT:    0 |     (D vbtable pointer)
+// CHECK-NEXT:    4 |     struct B b (empty)
+// CHECK:         8 |   struct B (base) (empty)
+// CHECK-NEXT:    8 |   struct C (virtual base)
+// CHECK-NEXT:    8 |     int a
+// CHECK-NEXT:      | [sizeof=12, align=4
+// CHECK-NEXT:      |  nvsize=8, nvalign=4]
+// CHECK-X64: *** Dumping AST Record Layout
+// CHECK-X64: *** Dumping AST Record Layout
+// CHECK-X64: *** Dumping AST Record Layout
+// CHECK-X64: *** Dumping AST Record Layout
+// CHECK-X64-NEXT:   0 | struct E
+// CHECK-X64-NEXT:   0 |   struct D (base)
+// CHECK-X64-NEXT:   8 |     struct B (base) (empty)
+// CHECK-X64-NEXT:   0 |     (D vbtable pointer)
+// CHECK-X64-NEXT:   8 |     struct B b (empty)
+// CHECK-X64:       16 |   struct B (base) (empty)
+// CHECK-X64-NEXT:  16 |   struct C (virtual base)
+// CHECK-X64-NEXT:  16 |     int a
+// CHECK-X64-NEXT:     | [sizeof=24, align=8
+// CHECK-X64-NEXT:     |  nvsize=16, nvalign=8]
+
+struct F : virtual D, virtual B {};
+// CHECK: *** Dumping AST Record Layout
+// CHECK-NEXT:    0 | struct F
+// CHECK-NEXT:    0 |   (F vbtable pointer)
+// CHECK-NEXT:    4 |   struct C (virtual base)
+// CHECK-NEXT:    4 |     int a
+// CHECK-NEXT:    8 |   struct D (virtual base)
+// CHECK-NEXT:   12 |     struct B (base) (empty)
+// CHECK-NEXT:    8 |     (D vbtable pointer)
+// CHECK-NEXT:   12 |     struct B b (empty)
+// CHECK:        16 |   struct B (virtual base) (empty)
+// CHECK-NEXT:      | [sizeof=16, align=4
+// CHECK-NEXT:      |  nvsize=4, nvalign=4]
+// CHECK-X64: *** Dumping AST Record Layout
+// CHECK-X64-NEXT:    0 | struct F
+// CHECK-X64-NEXT:    0 |   (F vbtable pointer)
+// CHECK-X64-NEXT:    8 |   struct C (virtual base)
+// CHECK-X64-NEXT:    8 |     int a
+// CHECK-X64-NEXT:   16 |   struct D (virtual base)
+// CHECK-X64-NEXT:   24 |     struct B (base) (empty)
+// CHECK-X64-NEXT:   16 |     (D vbtable pointer)
+// CHECK-X64-NEXT:   24 |     struct B b (empty)
+// CHECK-X64:        32 |   struct B (virtual base) (empty)
+// CHECK-X64-NEXT:      | [sizeof=32, align=8
+// CHECK-X64-NEXT:      |  nvsize=8, nvalign=8]
+
 int a[
 sizeof(AT3) +
 sizeof(BT3) +
-sizeof(T3)];
+sizeof(T3) +
+sizeof(E) +
+sizeof(F) +
+0];