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MS ABI: Up the required alignment after inserting padding between vbases 

We would correctly insert sufficiently aligned padding between vbases
when our leading base was empty, however we would neglect to increase
the required alignment of the most derived class.

This fixes PR20315.

llvm-svn: 213123
This commit is contained in:
David Majnemer 2014-07-16 07:16:58 +00:00
parent 1272764b18
commit bf3d430163
2 changed files with 58 additions and 1 deletions
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4
clang/lib/AST/RecordLayoutBuilder.cpp
View File

@ -2613,8 +2613,10 @@ void MicrosoftRecordLayoutBuilder::layoutVirtualBases(const CXXRecordDecl *RD) {
// bytes (in both 32 and 64 bits modes) and always involves rounding up to
// the required alignment, we don't know why.
if ((PreviousBaseLayout && PreviousBaseLayout->hasZeroSizedSubObject() &&
BaseLayout.leadsWithZeroSizedBase()) || HasVtordisp)
BaseLayout.leadsWithZeroSizedBase()) || HasVtordisp) {
Size = Size.RoundUpToAlignment(VtorDispAlignment) + VtorDispSize;
RequiredAlignment = VtorDispAlignment;
}
// Insert the virtual base.
ElementInfo Info = getAdjustedElementInfo(BaseLayout);
CharUnits BaseOffset = Size.RoundUpToAlignment(Info.Alignment);

55
clang/test/Layout/ms-x86-pack-and-align.cpp
View File

@ -544,6 +544,60 @@ struct RE {
// CHECK-X64-NEXT: | [sizeof=1029, align=1
// CHECK-X64-NEXT: | nvsize=1029, nvalign=1]
struct NA {};
struct NB {};
#pragma pack(push, 1)
struct NC : virtual NA, virtual NB {};
#pragma pack(pop)
struct ND : NC {};
// CHECK: *** Dumping AST Record Layout
// CHECK-NEXT: 0 | struct NA (empty)
// CHECK-NEXT: | [sizeof=1, align=1
// CHECK-NEXT: | nvsize=0, nvalign=1]
// CHECK: *** Dumping AST Record Layout
// CHECK-NEXT: 0 | struct NB (empty)
// CHECK-NEXT: | [sizeof=1, align=1
// CHECK-NEXT: | nvsize=0, nvalign=1]
// CHECK: *** Dumping AST Record Layout
// CHECK-NEXT: 0 | struct NC
// CHECK-NEXT: 0 | (NC vbtable pointer)
// CHECK-NEXT: 4 | struct NA (virtual base) (empty)
// CHECK-NEXT: 8 | struct NB (virtual base) (empty)
// CHECK-NEXT: | [sizeof=8, align=1
// CHECK-NEXT: | nvsize=4, nvalign=1]
// CHECK: *** Dumping AST Record Layout
// CHECK-NEXT: 0 | struct ND
// CHECK-NEXT: 0 | struct NC (base)
// CHECK-NEXT: 0 | (NC vbtable pointer)
// CHECK-NEXT: 4 | struct NA (virtual base) (empty)
// CHECK-NEXT: 8 | struct NB (virtual base) (empty)
// CHECK-NEXT: | [sizeof=8, align=4
// CHECK-NEXT: | nvsize=4, nvalign=4]
// CHECK-X64: *** Dumping AST Record Layout
// CHECK-X64-NEXT: 0 | struct NA (empty)
// CHECK-X64-NEXT: | [sizeof=1, align=1
// CHECK-X64-NEXT: | nvsize=0, nvalign=1]
// CHECK-X64: *** Dumping AST Record Layout
// CHECK-X64-NEXT: 0 | struct NB (empty)
// CHECK-X64-NEXT: | [sizeof=1, align=1
// CHECK-X64-NEXT: | nvsize=0, nvalign=1]
// CHECK-X64: *** Dumping AST Record Layout
// CHECK-X64-NEXT: 0 | struct NC
// CHECK-X64-NEXT: 0 | (NC vbtable pointer)
// CHECK-X64-NEXT: 8 | struct NA (virtual base) (empty)
// CHECK-X64-NEXT: 12 | struct NB (virtual base) (empty)
// CHECK-X64-NEXT: | [sizeof=12, align=1
// CHECK-X64-NEXT: | nvsize=8, nvalign=1]
// CHECK-X64: *** Dumping AST Record Layout
// CHECK-X64-NEXT: 0 | struct ND
// CHECK-X64-NEXT: 0 | struct NC (base)
// CHECK-X64-NEXT: 0 | (NC vbtable pointer)
// CHECK-X64-NEXT: 8 | struct NA (virtual base) (empty)
// CHECK-X64-NEXT: 12 | struct NB (virtual base) (empty)
// CHECK-X64-NEXT: | [sizeof=12, align=4
// CHECK-X64-NEXT: | nvsize=8, nvalign=4]
int a[
sizeof(X)+
sizeof(Y)+
@ -568,4 +622,5 @@ sizeof(RB2)+
sizeof(RB3)+
sizeof(RC)+
sizeof(RE)+
sizeof(ND)+
0];