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[vm] Verify there is no padding between last field and variable-length payload in the VM objects

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The implicit padding would not be initialized but would
be scanned by GC.

TEST=Manually tested with implicit padding.

Change-Id: Ia3556d3e42a97fbb2d8f67541d2e7de9b7650077
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/494566
Reviewed-by: Slava Egorov <vegorov@google.com>
Commit-Queue: Alexander Markov <alexmarkov@google.com>
Reviewed-by: Ryan Macnak <rmacnak@google.com>
This commit is contained in:
Alexander Markov
2026-04-13 08:52:24 -07:00
committed by dart-scoped@luci-project-accounts.iam.gserviceaccount.com
parent 256878a672
commit c3589b02b4
1 changed files with 19 additions and 12 deletions
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runtime/vm/raw_object.h
+19 -12
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@@ -104,7 +104,7 @@ class TypeParameterTypeDeserializationCluster;
&last##_); \
}
#define VISIT_TO_PAYLOAD_END(elem_type) \
#define VISIT_TO_PAYLOAD_END(elem_type, last_field) \
static_assert(is_uncompressed_ptr<elem_type>::value || \
is_compressed_ptr<elem_type>::value, \
"Payload elements must be object pointers"); \
@@ -113,6 +113,8 @@ class TypeParameterTypeDeserializationCluster;
CHECK_CONTAIN_COMPRESSED(elem_type); \
base_ptr_type<elem_type>::type* to(intptr_t length) { \
const uword payload_start = reinterpret_cast<uword>(this) + sizeof(*this); \
/* Ensure there is no padding between the last field and payload. */ \
ASSERT(reinterpret_cast<uword>(&last_field##_ + 1) == payload_start); \
ASSERT(Utils::IsAligned(payload_start, sizeof(elem_type))); \
const uword payload_last = \
payload_start + sizeof(elem_type) * (length - 1); \
@@ -1054,7 +1056,7 @@ inline intptr_t ObjectPtr::GetClassId() const {
protected: \
Compressed##type name##_;
#define VARIABLE_POINTER_FIELDS(type, accessor_name, array_name) \
#define VARIABLE_POINTER_FIELDS(type, accessor_name, array_name, last_field) \
public: \
type accessor_name(intptr_t index) const { \
return LoadPointer<type>(&array_name()[index]); \
@@ -1085,9 +1087,10 @@ inline intptr_t ObjectPtr::GetClassId() const {
type const* array_name() const { \
OPEN_ARRAY_START(type, type); \
} \
VISIT_TO_PAYLOAD_END(type)
VISIT_TO_PAYLOAD_END(type, last_field)
#define COMPRESSED_VARIABLE_POINTER_FIELDS(type, accessor_name, array_name) \
#define COMPRESSED_VARIABLE_POINTER_FIELDS(type, accessor_name, array_name, \
last_field) \
public: \
type accessor_name(intptr_t index) const { \
return LoadCompressedPointer<type, Compressed##type>( \
@@ -1124,7 +1127,7 @@ inline intptr_t ObjectPtr::GetClassId() const {
Compressed##type const* array_name() const { \
OPEN_ARRAY_START(Compressed##type, Compressed##type); \
} \
VISIT_TO_PAYLOAD_END(Compressed##type)
VISIT_TO_PAYLOAD_END(Compressed##type, last_field)
#define SMI_FIELD(type, name) \
public: \
@@ -1983,7 +1986,7 @@ class UntaggedWeakArray : public UntaggedObject {
COMPRESSED_SMI_FIELD(SmiPtr, length)
VISIT_FROM(length)
// Variable length data follows here.
COMPRESSED_VARIABLE_POINTER_FIELDS(ObjectPtr, element, data)
COMPRESSED_VARIABLE_POINTER_FIELDS(ObjectPtr, element, data, length)
template <typename Table, bool kAllCanonicalObjectsAreIncludedIntoSet>
friend class CanonicalSetDeserializationCluster;
@@ -2544,7 +2547,7 @@ class UntaggedLocalVarDescriptors : public UntaggedObject {
uword num_entries_;
VISIT_FROM_PAYLOAD_START(CompressedStringPtr)
COMPRESSED_VARIABLE_POINTER_FIELDS(StringPtr, name, names)
COMPRESSED_VARIABLE_POINTER_FIELDS(StringPtr, name, names, num_entries)
CompressedStringPtr* nameAddrAt(intptr_t i) { return &(names()[i]); }
@@ -2600,7 +2603,7 @@ class UntaggedContext : public UntaggedObject {
COMPRESSED_POINTER_FIELD(ContextPtr, parent)
VISIT_FROM(parent)
// Variable length data follows here.
COMPRESSED_VARIABLE_POINTER_FIELDS(ObjectPtr, element, data)
COMPRESSED_VARIABLE_POINTER_FIELDS(ObjectPtr, element, data, parent)
friend class Object;
friend class Interpreter;
@@ -2921,7 +2924,10 @@ class UntaggedTypeArguments : public UntaggedInstance {
COMPRESSED_SMI_FIELD(SmiPtr, hash)
COMPRESSED_SMI_FIELD(SmiPtr, nullability)
// Variable length data follows here.
COMPRESSED_VARIABLE_POINTER_FIELDS(AbstractTypePtr, element, types)
COMPRESSED_VARIABLE_POINTER_FIELDS(AbstractTypePtr,
element,
types,
nullability)
friend class Object;
friend class Interpreter;
@@ -3193,13 +3199,14 @@ class UntaggedClosure : public UntaggedInstance {
COMPRESSED_SMI_FIELD(SmiPtr, hash)
COMPRESSED_POINTER_FIELD(FunctionPtr, function)
public:
// Variable length data follows here.
// It contains (in order):
// - delayed type arguments (if function is generic);
// - instantiator type arguments (if enclosing class is generic);
// - parent function type arguments (if enclosing function has type args);
// - captured values and contexts.
COMPRESSED_VARIABLE_POINTER_FIELDS(ObjectPtr, element, data)
COMPRESSED_VARIABLE_POINTER_FIELDS(ObjectPtr, element, data, function)
CompressedObjectPtr* to_snapshot(Snapshot::Kind kind, intptr_t num_elements) {
return to(num_elements);
@@ -3477,7 +3484,7 @@ class UntaggedArray : public UntaggedInstance {
VISIT_FROM(type_arguments)
COMPRESSED_SMI_FIELD(SmiPtr, length)
// Variable length data follows here.
COMPRESSED_VARIABLE_POINTER_FIELDS(ObjectPtr, element, data)
COMPRESSED_VARIABLE_POINTER_FIELDS(ObjectPtr, element, data, length)
friend class MapSerializationCluster;
friend class MapDeserializationCluster;
@@ -3629,7 +3636,7 @@ class UntaggedRecord : public UntaggedInstance {
COMPRESSED_SMI_FIELD(SmiPtr, shape)
VISIT_FROM(shape)
// Variable length data follows here.
COMPRESSED_VARIABLE_POINTER_FIELDS(ObjectPtr, field, data)
COMPRESSED_VARIABLE_POINTER_FIELDS(ObjectPtr, field, data, shape)
friend void UpdateLengthField(intptr_t, ObjectPtr,
ObjectPtr); // shape_