https://github.com/tbaederr updated
https://github.com/llvm/llvm-project/pull/137159
>From a489e3957eeb23fc38758c9a6670a3abd082321d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Timm=20B=C3=A4der?= <tbae...@redhat.com>
Date: Thu, 24 Apr 2025 13:19:25 +0200
Subject: [PATCH] [clang][bytecode] Diagnose comparing pointers to fields...
... with different access specifiers.
---
clang/lib/AST/ByteCode/Interp.h | 13 +++++++++
clang/lib/AST/ByteCode/Pointer.cpp | 42 +++++++++++++++++++++++++++++
clang/lib/AST/ByteCode/Pointer.h | 9 ++++++-
clang/test/AST/ByteCode/records.cpp | 23 ++++++++++++++++
4 files changed, 86 insertions(+), 1 deletion(-)
diff --git a/clang/lib/AST/ByteCode/Interp.h b/clang/lib/AST/ByteCode/Interp.h
index 99b032bee9e3d..0a52a64240c04 100644
--- a/clang/lib/AST/ByteCode/Interp.h
+++ b/clang/lib/AST/ByteCode/Interp.h
@@ -1007,6 +1007,19 @@ inline bool CmpHelper<Pointer>(InterpState &S, CodePtr
OpPC, CompareFn Fn) {
return false;
}
+ // Diagnose comparisons between fields with different access specifiers.
+ if (std::optional<std::pair<Pointer, Pointer>> Split =
+ Pointer::computeSplitPoint(LHS, RHS)) {
+ const FieldDecl *LF = Split->first.getField();
+ const FieldDecl *RF = Split->second.getField();
+ if (LF && RF && !LF->getParent()->isUnion() &&
+ LF->getAccess() != RF->getAccess()) {
+ S.CCEDiag(S.Current->getSource(OpPC),
+ diag::note_constexpr_pointer_comparison_differing_access)
+ << LF << LF->getAccess() << RF << RF->getAccess() << LF->getParent();
+ }
+ }
+
unsigned VL = LHS.getByteOffset();
unsigned VR = RHS.getByteOffset();
S.Stk.push<BoolT>(BoolT::from(Fn(Compare(VL, VR))));
diff --git a/clang/lib/AST/ByteCode/Pointer.cpp
b/clang/lib/AST/ByteCode/Pointer.cpp
index 059503cae3561..6c2566ba20bde 100644
--- a/clang/lib/AST/ByteCode/Pointer.cpp
+++ b/clang/lib/AST/ByteCode/Pointer.cpp
@@ -571,6 +571,48 @@ bool Pointer::pointsToLiteral() const {
return E && !isa<MaterializeTemporaryExpr, StringLiteral>(E);
}
+std::optional<std::pair<Pointer, Pointer>>
+Pointer::computeSplitPoint(const Pointer &A, const Pointer &B) {
+ if (!A.isBlockPointer() || !B.isBlockPointer())
+ return std::nullopt;
+
+ if (A.asBlockPointer().Pointee != B.asBlockPointer().Pointee)
+ return std::nullopt;
+ if (A.isRoot() && B.isRoot())
+ return std::nullopt;
+
+ if (A == B)
+ return std::make_pair(A, B);
+
+ auto getBase = [](const Pointer &P) -> Pointer {
+ if (P.isArrayElement())
+ return P.expand().getArray();
+ return P.getBase();
+ };
+
+ Pointer IterA = A;
+ Pointer IterB = B;
+ Pointer CurA = IterA;
+ Pointer CurB = IterB;
+ for (;;) {
+ if (IterA.asBlockPointer().Base > IterB.asBlockPointer().Base) {
+ CurA = IterA;
+ IterA = getBase(IterA);
+ } else {
+ CurB = IterB;
+ IterB = getBase(IterB);
+ }
+
+ if (IterA == IterB)
+ return std::make_pair(CurA, CurB);
+
+ if (IterA.isRoot() && IterB.isRoot())
+ return std::nullopt;
+ }
+
+ llvm_unreachable("The loop above should've returned.");
+}
+
std::optional<APValue> Pointer::toRValue(const Context &Ctx,
QualType ResultType) const {
const ASTContext &ASTCtx = Ctx.getASTContext();
diff --git a/clang/lib/AST/ByteCode/Pointer.h b/clang/lib/AST/ByteCode/Pointer.h
index 8ede706f2736f..e168154a55f58 100644
--- a/clang/lib/AST/ByteCode/Pointer.h
+++ b/clang/lib/AST/ByteCode/Pointer.h
@@ -492,7 +492,11 @@ class Pointer {
return ElemDesc ? ElemDesc->ElemRecord : nullptr;
}
/// Returns the field information.
- const FieldDecl *getField() const { return getFieldDesc()->asFieldDecl(); }
+ const FieldDecl *getField() const {
+ if (const Descriptor *FD = getFieldDesc())
+ return FD->asFieldDecl();
+ return nullptr;
+ }
/// Checks if the storage is extern.
bool isExtern() const {
@@ -724,6 +728,9 @@ class Pointer {
/// Checks if both given pointers point to the same block.
static bool pointToSameBlock(const Pointer &A, const Pointer &B);
+ static std::optional<std::pair<Pointer, Pointer>>
+ computeSplitPoint(const Pointer &A, const Pointer &B);
+
/// Whether this points to a block that's been created for a "literal
lvalue",
/// i.e. a non-MaterializeTemporaryExpr Expr.
bool pointsToLiteral() const;
diff --git a/clang/test/AST/ByteCode/records.cpp
b/clang/test/AST/ByteCode/records.cpp
index da851785323a5..b4059f009b887 100644
--- a/clang/test/AST/ByteCode/records.cpp
+++ b/clang/test/AST/ByteCode/records.cpp
@@ -1787,3 +1787,26 @@ namespace IntegralBaseCast {
static_assert(f() == 0, "");
}
+
+namespace AccessMismatch {
+ struct A {
+ public:
+ constexpr A() : a(0), b(0) {}
+ int a;
+ constexpr bool cmp() const { return &a < &b; } // both-note {{comparison
of address of fields 'a' and 'b' of 'A' with differing access specifiers
(public vs private) has unspecified value}}
+ private:
+ int b;
+ };
+ static_assert(A().cmp(), ""); // both-error {{constant expression}} \
+ // both-note {{in call}}
+
+ class B {
+ public:
+ A a;
+ constexpr bool cmp() const { return &a.a < &b.a; } // both-note
{{comparison of address of fields 'a' and 'b' of 'B' with differing access
specifiers (public vs protected) has unspecified value}}
+ protected:
+ A b;
+ };
+ static_assert(B().cmp(), ""); // both-error {{constant expression}} \
+ // both-note {{in call}}
+}
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