https://github.com/tbaederr created
https://github.com/llvm/llvm-project/pull/133852
Union members get the same address, so we can't just use
`Pointer::getByteOffset()`.
>From fa0d8971671cb28df72d9a4712f6be951a367145 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Timm=20B=C3=A4der?= <tbae...@redhat.com>
Date: Tue, 1 Apr 2025 06:07:19 +0200
Subject: [PATCH] [clang][bytecode] Fix comparing the addresses of union
members
Union members get the same address, so we can't just use
`Pointer::getByteOffset()`.
---
clang/lib/AST/ByteCode/Interp.h | 11 ++++++++-
clang/lib/AST/ByteCode/Pointer.cpp | 31 ++++++++++++++++++++++++
clang/lib/AST/ByteCode/Pointer.h | 4 +++-
clang/test/AST/ByteCode/unions.cpp | 38 ++++++++++++++++++++++++++++++
4 files changed, 82 insertions(+), 2 deletions(-)
diff --git a/clang/lib/AST/ByteCode/Interp.h b/clang/lib/AST/ByteCode/Interp.h
index 938077a9f10ae..6fe1d4b1f95ae 100644
--- a/clang/lib/AST/ByteCode/Interp.h
+++ b/clang/lib/AST/ByteCode/Interp.h
@@ -1070,9 +1070,18 @@ inline bool CmpHelperEQ<Pointer>(InterpState &S, CodePtr
OpPC, CompareFn Fn) {
}
if (Pointer::hasSameBase(LHS, RHS)) {
+ if (LHS.inUnion() && RHS.inUnion()) {
+ // If the pointers point into a union, things are a little more
+ // complicated since the offset we save in interp::Pointer can't be used
+ // to compare the pointers directly.
+ size_t A = LHS.computeOffsetForComparison();
+ size_t B = RHS.computeOffsetForComparison();
+ S.Stk.push<BoolT>(BoolT::from(Fn(Compare(A, B))));
+ return true;
+ }
+
unsigned VL = LHS.getByteOffset();
unsigned VR = RHS.getByteOffset();
-
// In our Pointer class, a pointer to an array and a pointer to the first
// element in the same array are NOT equal. They have the same Base value,
// but a different Offset. This is a pretty rare case, so we fix this here
diff --git a/clang/lib/AST/ByteCode/Pointer.cpp
b/clang/lib/AST/ByteCode/Pointer.cpp
index 79b47c26992ae..7ccefd6aeb9e1 100644
--- a/clang/lib/AST/ByteCode/Pointer.cpp
+++ b/clang/lib/AST/ByteCode/Pointer.cpp
@@ -339,6 +339,37 @@ void Pointer::print(llvm::raw_ostream &OS) const {
}
}
+/// Compute an integer that can be used to compare this pointer to
+/// another one.
+size_t Pointer::computeOffsetForComparison() const {
+ if (!isBlockPointer())
+ return Offset;
+
+ size_t Result = 0;
+ Pointer P = *this;
+ while (!P.isRoot()) {
+ if (P.isArrayRoot()) {
+ P = P.getBase();
+ continue;
+ }
+ if (P.isArrayElement()) {
+ Result += (P.getIndex() * P.elemSize());
+ P = P.getArray();
+ }
+
+ if (const Record *R = P.getBase().getRecord(); R && R->isUnion()) {
+ // Direct child of a union - all have offset 0.
+ P = P.getBase();
+ continue;
+ }
+
+ Result += P.getInlineDesc()->Offset;
+ P = P.getBase();
+ }
+
+ return Result;
+}
+
std::string Pointer::toDiagnosticString(const ASTContext &Ctx) const {
if (isZero())
return "nullptr";
diff --git a/clang/lib/AST/ByteCode/Pointer.h b/clang/lib/AST/ByteCode/Pointer.h
index fd33ee9955f55..988237d39fff4 100644
--- a/clang/lib/AST/ByteCode/Pointer.h
+++ b/clang/lib/AST/ByteCode/Pointer.h
@@ -417,7 +417,7 @@ class Pointer {
return false;
}
bool inUnion() const {
- if (isBlockPointer())
+ if (isBlockPointer() && asBlockPointer().Base >= sizeof(InlineDescriptor))
return getInlineDesc()->InUnion;
return false;
};
@@ -727,6 +727,8 @@ class Pointer {
/// Prints the pointer.
void print(llvm::raw_ostream &OS) const;
+ size_t computeOffsetForComparison() const;
+
private:
friend class Block;
friend class DeadBlock;
diff --git a/clang/test/AST/ByteCode/unions.cpp
b/clang/test/AST/ByteCode/unions.cpp
index 66b8389606b85..3911a2b2f7dde 100644
--- a/clang/test/AST/ByteCode/unions.cpp
+++ b/clang/test/AST/ByteCode/unions.cpp
@@ -600,3 +600,41 @@ namespace MoveOrAssignOp {
static_assert(foo());
}
#endif
+
+namespace AddressComparison {
+ union {
+ int a;
+ int c;
+ } U;
+ static_assert(__builtin_addressof(U.a) == (void*)__builtin_addressof(U.c));
+ static_assert(&U.a == &U.c);
+
+
+ struct {
+ union {
+ struct {
+ int a;
+ int b;
+ } a;
+ struct {
+ int b;
+ int a;
+ }b;
+ } u;
+ int b;
+ } S;
+
+ static_assert(&S.u.a.a == &S.u.b.b);
+ static_assert(&S.u.a.b != &S.u.b.b);
+ static_assert(&S.u.a.b == &S.u.b.b); // both-error {{failed}}
+
+
+ union {
+ int a[2];
+ int b[2];
+ } U2;
+
+ static_assert(&U2.a[0] == &U2.b[0]);
+ static_assert(&U2.a[0] != &U2.b[1]);
+ static_assert(&U2.a[0] == &U2.b[1]); // both-error {{failed}}
+}
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