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[clang][bytecode] Mark CXXDefaultInitExprs in InitLink chain #166395

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Merged
merged 1 commit into from
Nov 11, 2025
Merged

[clang][bytecode] Mark CXXDefaultInitExprs in InitLink chain #166395

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11 changes: 6 additions & 5 deletions clang/lib/AST/ByteCode/Compiler.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -5432,8 +5432,7 @@ bool Compiler<Emitter>::VisitCXXThisExpr(const CXXThisExpr *E) {
unsigned EndIndex = 0;
// Find the init list.
for (StartIndex = InitStack.size() - 1; StartIndex > 0; --StartIndex) {
if (InitStack[StartIndex].Kind == InitLink::K_InitList ||
InitStack[StartIndex].Kind == InitLink::K_This) {
if (InitStack[StartIndex].Kind == InitLink::K_DIE) {
EndIndex = StartIndex;
--StartIndex;
break;
Expand All @@ -5446,7 +5445,8 @@ bool Compiler<Emitter>::VisitCXXThisExpr(const CXXThisExpr *E) {
continue;

if (InitStack[StartIndex].Kind != InitLink::K_Field &&
InitStack[StartIndex].Kind != InitLink::K_Elem)
InitStack[StartIndex].Kind != InitLink::K_Elem &&
InitStack[StartIndex].Kind != InitLink::K_DIE)
break;
}

Expand All @@ -5457,7 +5457,8 @@ bool Compiler<Emitter>::VisitCXXThisExpr(const CXXThisExpr *E) {

// Emit the instructions.
for (unsigned I = StartIndex; I != (EndIndex + 1); ++I) {
if (InitStack[I].Kind == InitLink::K_InitList)
if (InitStack[I].Kind == InitLink::K_InitList ||
InitStack[I].Kind == InitLink::K_DIE)
continue;
if (!InitStack[I].template emit<Emitter>(this, E))
return false;
Expand Down Expand Up @@ -6328,8 +6329,8 @@ bool Compiler<Emitter>::compileConstructor(const CXXConstructorDecl *Ctor) {

unsigned FirstLinkOffset =
R->getField(cast<FieldDecl>(IFD->chain()[0]))->Offset;
InitStackScope<Emitter> ISS(this, isa<CXXDefaultInitExpr>(InitExpr));
InitLinkScope<Emitter> ILS(this, InitLink::Field(FirstLinkOffset));
InitStackScope<Emitter> ISS(this, isa<CXXDefaultInitExpr>(InitExpr));
if (!emitFieldInitializer(NestedField, NestedFieldOffset, InitExpr,
IsUnion))
return false;
Expand Down
17 changes: 13 additions & 4 deletions clang/lib/AST/ByteCode/Compiler.h
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Expand Up @@ -52,12 +52,14 @@ struct InitLink {
K_Decl = 3,
K_Elem = 5,
K_RVO = 6,
K_InitList = 7
K_InitList = 7,
K_DIE = 8,
Copy link
Collaborator

@shafik shafik Nov 19, 2025

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What does DIE stand for here? The rest of the fields are mostly self explanatory. Either a different name or a comment would help. Also DIE is a dwarf think and so we are now overloading the term, which is not good.

};

static InitLink This() { return InitLink{K_This}; }
static InitLink InitList() { return InitLink{K_InitList}; }
static InitLink RVO() { return InitLink{K_RVO}; }
static InitLink DIE() { return InitLink{K_DIE}; }
static InitLink Field(unsigned Offset) {
InitLink IL{K_Field};
IL.Offset = Offset;
Expand Down Expand Up @@ -668,22 +670,29 @@ template <class Emitter> class InitLinkScope final {

~InitLinkScope() { this->Ctx->InitStack.pop_back(); }

private:
public:
Compiler<Emitter> *Ctx;
};

template <class Emitter> class InitStackScope final {
public:
InitStackScope(Compiler<Emitter> *Ctx, bool Active)
: Ctx(Ctx), OldValue(Ctx->InitStackActive) {
: Ctx(Ctx), OldValue(Ctx->InitStackActive), Active(Active) {
Ctx->InitStackActive = Active;
if (Active)
Ctx->InitStack.push_back(InitLink::DIE());
}

~InitStackScope() { this->Ctx->InitStackActive = OldValue; }
~InitStackScope() {
this->Ctx->InitStackActive = OldValue;
if (Active)
Ctx->InitStack.pop_back();
}

private:
Compiler<Emitter> *Ctx;
bool OldValue;
bool Active;
};

} // namespace interp
Expand Down
21 changes: 21 additions & 0 deletions clang/test/AST/ByteCode/cxx14.cpp
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Expand Up @@ -7,3 +7,24 @@ constexpr int(*null_ptr)() = nullptr;
constexpr int test4 = (*null_ptr)(); // both-error {{must be initialized by a constant expression}} \
// both-note {{evaluates to a null function pointer}}

struct E {
int n = 0;
struct {
void *x = this;
};
void *y = this;
};
constexpr E e1 = E();
static_assert(e1.x != e1.y, "");
constexpr E e2 = E{0};
static_assert(e2.x != e2.y, "");

struct S {
int &&a = 2;
int b[1]{a};
};
constexpr int foo() {
S s{12};
return s.b[0];
}
static_assert(foo() == 12, "");
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