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Merged
merged 2 commits into from
Sep 27, 2023
Merged

PR for llvm/llvm-project#65982 #703

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7ae78be
[clang] Bail out when handling union access with virtual inheritance
antoniofrighetto Sep 13, 2023
df3e2c4
[clang] Include `expected-no-diagnostics` in newly-added test (NFC)
antoniofrighetto Sep 14, 2023
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17 changes: 12 additions & 5 deletions clang/lib/AST/ExprConstant.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -6013,8 +6013,9 @@ const AccessKinds StartLifetimeOfUnionMemberHandler::AccessKind;
/// operator whose left-hand side might involve a union member access. If it
/// does, implicitly start the lifetime of any accessed union elements per
/// C++20 [class.union]5.
static bool HandleUnionActiveMemberChange(EvalInfo &Info, const Expr *LHSExpr,
const LValue &LHS) {
static bool MaybeHandleUnionActiveMemberChange(EvalInfo &Info,
const Expr *LHSExpr,
const LValue &LHS) {
if (LHS.InvalidBase || LHS.Designator.Invalid)
return false;

Expand Down Expand Up @@ -6069,8 +6070,14 @@ static bool HandleUnionActiveMemberChange(EvalInfo &Info, const Expr *LHSExpr,
break;
// Walk path backwards as we walk up from the base to the derived class.
for (const CXXBaseSpecifier *Elt : llvm::reverse(ICE->path())) {
if (Elt->isVirtual()) {
// A class with virtual base classes never has a trivial default
// constructor, so S(E) is empty in this case.
E = nullptr;
break;
}

--PathLength;
(void)Elt;
assert(declaresSameEntity(Elt->getType()->getAsCXXRecordDecl(),
LHS.Designator.Entries[PathLength]
.getAsBaseOrMember().getPointer()));
Expand Down Expand Up @@ -7748,7 +7755,7 @@ class ExprEvaluatorBase
// per C++20 [class.union]5.
if (Info.getLangOpts().CPlusPlus20 && OCE &&
OCE->getOperator() == OO_Equal && MD->isTrivial() &&
!HandleUnionActiveMemberChange(Info, Args[0], ThisVal))
!MaybeHandleUnionActiveMemberChange(Info, Args[0], ThisVal))
return false;

Args = Args.slice(1);
Expand Down Expand Up @@ -8621,7 +8628,7 @@ bool LValueExprEvaluator::VisitBinAssign(const BinaryOperator *E) {
return false;

if (Info.getLangOpts().CPlusPlus20 &&
!HandleUnionActiveMemberChange(Info, E->getLHS(), Result))
!MaybeHandleUnionActiveMemberChange(Info, E->getLHS(), Result))
return false;

return handleAssignment(this->Info, E, Result, E->getLHS()->getType(),
Expand Down
13 changes: 13 additions & 0 deletions clang/test/SemaCXX/cxx2a-virtual-base-used.cpp
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Original file line number Diff line number Diff line change
@@ -0,0 +1,13 @@
// RUN: %clang_cc1 -std=c++2a -verify -triple=x86_64-linux-gnu %s
// expected-no-diagnostics

// Fixes assertion triggered by https://github.com/llvm/llvm-project/issues/65982

struct A { int y; };
struct B : virtual public A {};
struct X : public B {};

void member_with_virtual_inheritance() {
X x;
x.B::y = 1;
}