dnrops
/
clang
mirror of https://github.com/microsoft/clang.git
1
0
Fork 0
Code Issues Packages Projects Releases Wiki Activity

[MS] Fix bug in method vfptr location code 

We were assuming that vbtable indices were assigned in layout order in
our comparison, which is not the case. When a virtual method, such as
the destructor, appears in multiple vftables, the vftable that appears
first in object layout order is the one that points to the main
implementation of that method. The later vftables use thunks.

In this layout, we adjusted "this" in the main implementation by the
amount that is appropriate for 'B' instead of 'A', even though the main
implementation is found in D's vftable for A:

  struct A {
    virtual ~A() {}
  };
  struct B {
    virtual ~B() {}
  };
  struct C : virtual B {};
  struct D : virtual A, C {};

D's layout looks like:
   0 D subobject (empty)
   0 C base suboject
   8 A base subobject
  16 B base subobject

With this fix, we correctly adjust by -8 in D's deleting destructor
instead of -16.

Fixes PR36921.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@328723 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Reid Kleckner 2018-03-28 18:23:35 +00:00
parent 873ca69ee1
commit e3fdb5e25a
2 changed files with 38 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

26
lib/AST/VTableBuilder.cpp
View File

@ -3544,6 +3544,19 @@ static void computeFullPathsForVFTables(ASTContext &Context,
}
}
static bool
vfptrIsEarlierInMDC(const ASTRecordLayout &Layout,
const MicrosoftVTableContext::MethodVFTableLocation &LHS,
const MicrosoftVTableContext::MethodVFTableLocation &RHS) {
CharUnits L = LHS.VFPtrOffset;
CharUnits R = RHS.VFPtrOffset;
if (LHS.VBase)
L += Layout.getVBaseClassOffset(LHS.VBase);
if (RHS.VBase)
R += Layout.getVBaseClassOffset(RHS.VBase);
return L < R;
}
void MicrosoftVTableContext::computeVTableRelatedInformation(
const CXXRecordDecl *RD) {
assert(RD->isDynamicClass());
@ -3574,12 +3587,15 @@ void MicrosoftVTableContext::computeVTableRelatedInformation(
EmptyAddressPointsMap);
Thunks.insert(Builder.thunks_begin(), Builder.thunks_end());
const ASTRecordLayout &Layout = Context.getASTRecordLayout(RD);
for (const auto &Loc : Builder.vtable_locations()) {
GlobalDecl GD = Loc.first;
MethodVFTableLocation NewLoc = Loc.second;
auto M = NewMethodLocations.find(GD);
if (M == NewMethodLocations.end() || NewLoc < M->second)
NewMethodLocations[GD] = NewLoc;
auto Insert = NewMethodLocations.insert(Loc);
if (!Insert.second) {
const MethodVFTableLocation &NewLoc = Loc.second;
MethodVFTableLocation &OldLoc = Insert.first->second;
if (vfptrIsEarlierInMDC(Layout, NewLoc, OldLoc))
OldLoc = NewLoc;
}
}
}

17
test/CodeGenCXX/microsoft-abi-virtual-inheritance.cpp
View File

@ -538,3 +538,20 @@ D::D() : C() {}
// CHECK: %[[FIELD:.*]] = getelementptr inbounds i8, i8* %[[C_i8]], i32 8
// CHECK: call void @llvm.memset.p0i8.i32(i8* align 4 %[[FIELD]], i8 0, i32 4, i1 false)
}
namespace pr36921 {
struct A {
virtual ~A() {}
};
struct B {
virtual ~B() {}
};
struct C : virtual B {};
struct D : virtual A, C {};
D d;
// CHECK-LABEL: define linkonce_odr dso_local x86_thiscallcc i8* @"??_GD@pr36921@@UAEPAXI@Z"(
// CHECK: %[[THIS:.*]] = load %"struct.pr36921::D"*, %"struct.pr36921::D"**
// CHECK: %[[THIS_UNADJ_i8:.*]] = bitcast %"struct.pr36921::D"* %[[THIS_RELOAD]] to i8*
// CHECK: %[[THIS_ADJ_i8:.*]] = getelementptr inbounds i8, i8* %[[THIS_UNADJ_i8]], i32 -4
// CHECK: %[[THIS:.*]] = bitcast i8* %[[THIS_ADJ_i8]] to %"struct.pr36921::D"*
}