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MS ABI: Pure virtual functions don't contribute to vtordisps 

Usually, overriding a virtual function defined in a virtual base
required emission of a vtordisp slot in the record.  However no vtordisp
is needed if the overriding function is pure; it should be impossible to
observe the pure virtual method.

This fixes PR21046.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@218340 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
David Majnemer 2014-09-23 22:58:15 +00:00
parent 86dc7fea0b
commit d1307f5687
2 changed files with 39 additions and 14 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

27
lib/AST/RecordLayoutBuilder.cpp
View File

@ -2181,8 +2181,9 @@ public:
FieldOffsets.push_back(FieldOffset);
}
/// \brief Compute the set of virtual bases for which vtordisps are required.
llvm::SmallPtrSet<const CXXRecordDecl *, 2>
computeVtorDispSet(const CXXRecordDecl *RD);
void computeVtorDispSet(
llvm::SmallPtrSetImpl<const CXXRecordDecl *> &HasVtorDispSet,
const CXXRecordDecl *RD) const;
const ASTContext &Context;
/// \brief The size of the record being laid out.
CharUnits Size;
@ -2605,14 +2606,14 @@ void MicrosoftRecordLayoutBuilder::layoutVirtualBases(const CXXRecordDecl *RD) {
}
VtorDispAlignment = std::max(VtorDispAlignment, RequiredAlignment);
// Compute the vtordisp set.
llvm::SmallPtrSet<const CXXRecordDecl *, 2> HasVtordispSet =
computeVtorDispSet(RD);
llvm::SmallPtrSet<const CXXRecordDecl *, 2> HasVtorDispSet;
computeVtorDispSet(HasVtorDispSet, RD);
// Iterate through the virtual bases and lay them out.
const ASTRecordLayout *PreviousBaseLayout = nullptr;
for (const CXXBaseSpecifier &VBase : RD->vbases()) {
const CXXRecordDecl *BaseDecl = VBase.getType()->getAsCXXRecordDecl();
const ASTRecordLayout &BaseLayout = Context.getASTRecordLayout(BaseDecl);
bool HasVtordisp = HasVtordispSet.count(BaseDecl);
bool HasVtordisp = HasVtorDispSet.count(BaseDecl) > 0;
// Insert padding between two bases if the left first one is zero sized or
// contains a zero sized subobject and the right is zero sized or one leads
// with a zero sized base. The padding between virtual bases is 4
@ -2671,10 +2672,9 @@ RequiresVtordisp(const llvm::SmallPtrSetImpl<const CXXRecordDecl *> &
return false;
}
llvm::SmallPtrSet<const CXXRecordDecl *, 2>
MicrosoftRecordLayoutBuilder::computeVtorDispSet(const CXXRecordDecl *RD) {
llvm::SmallPtrSet<const CXXRecordDecl *, 2> HasVtordispSet;
void MicrosoftRecordLayoutBuilder::computeVtorDispSet(
llvm::SmallPtrSetImpl<const CXXRecordDecl *> &HasVtordispSet,
const CXXRecordDecl *RD) const {
// /vd2 or #pragma vtordisp(2): Always use vtordisps for virtual bases with
// vftables.
if (RD->getMSVtorDispMode() == MSVtorDispAttr::ForVFTable) {
@ -2684,7 +2684,7 @@ MicrosoftRecordLayoutBuilder::computeVtorDispSet(const CXXRecordDecl *RD) {
if (Layout.hasExtendableVFPtr())
HasVtordispSet.insert(BaseDecl);
}
return HasVtordispSet;
return;
}
// If any of our bases need a vtordisp for this type, so do we. Check our
@ -2701,7 +2701,7 @@ MicrosoftRecordLayoutBuilder::computeVtorDispSet(const CXXRecordDecl *RD) {
// * #pragma vtordisp(0) or the /vd0 flag are in use.
if ((!RD->hasUserDeclaredConstructor() && !RD->hasUserDeclaredDestructor()) ||
RD->getMSVtorDispMode() == MSVtorDispAttr::Never)
return HasVtordispSet;
return;
// /vd1 or #pragma vtordisp(1): Try to guess based on whether we think it's
// possible for a partially constructed object with virtual base overrides to
// escape a non-trivial constructor.
@ -2712,9 +2712,9 @@ MicrosoftRecordLayoutBuilder::computeVtorDispSet(const CXXRecordDecl *RD) {
// vtordisp.
llvm::SmallPtrSet<const CXXMethodDecl *, 8> Work;
llvm::SmallPtrSet<const CXXRecordDecl *, 2> BasesWithOverriddenMethods;
// Seed the working set with our non-destructor virtual methods.
// Seed the working set with our non-destructor, non-pure virtual methods.
for (const CXXMethodDecl *MD : RD->methods())
if (MD->isVirtual() && !isa<CXXDestructorDecl>(MD))
if (MD->isVirtual() && !isa<CXXDestructorDecl>(MD) && !MD->isPure())
Work.insert(MD);
while (!Work.empty()) {
const CXXMethodDecl *MD = *Work.begin();
@ -2736,7 +2736,6 @@ MicrosoftRecordLayoutBuilder::computeVtorDispSet(const CXXRecordDecl *RD) {
RequiresVtordisp(BasesWithOverriddenMethods, BaseDecl))
HasVtordispSet.insert(BaseDecl);
}
return HasVtordispSet;
}
/// \brief Get or compute information about the layout of the specified record

26
test/Layout/ms-x86-vtordisp.cpp
View File

@ -416,6 +416,31 @@ struct HC : virtual HB {};
// CHECK-X64-NEXT: | [sizeof=32, align=8
// CHECK-X64-NEXT: | nvsize=8, nvalign=8]
struct IA {
virtual void f();
};
struct __declspec(dllexport) IB : virtual IA {
virtual void f() = 0;
IB() {}
};
// CHECK: *** Dumping AST Record Layout
// CHECK: *** Dumping AST Record Layout
// CHECK-NEXT: 0 | struct IB
// CHECK-NEXT: 0 | (IB vbtable pointer)
// CHECK-NEXT: 4 | struct IA (virtual base)
// CHECK-NEXT: 4 | (IA vftable pointer)
// CHECK-NEXT: | [sizeof=8, align=4
// CHECK-NEXT: | nvsize=4, nvalign=4]
// CHECK-X64: *** Dumping AST Record Layout
// CHECK-X64: *** Dumping AST Record Layout
// CHECK-X64-NEXT: 0 | struct IB
// CHECK-X64-NEXT: 0 | (IB vbtable pointer)
// CHECK-X64-NEXT: 8 | struct IA (virtual base)
// CHECK-X64-NEXT: 8 | (IA vftable pointer)
// CHECK-X64-NEXT: | [sizeof=16, align=8
// CHECK-X64-NEXT: | nvsize=8, nvalign=8]
int a[
sizeof(A)+
sizeof(C)+
@ -428,4 +453,5 @@ sizeof(pragma_test3::C)+
sizeof(pragma_test4::C)+
sizeof(GD)+
sizeof(HC)+
sizeof(IB)+
0];