dart-sdk/runtime/vm/raw_object_fields.h
Martin Kustermann 3669086a40 [vm] Fix field index information in heap snapshots in AOT
In AOT we can have unboxed fields that will not be visited by GC
visitors and as such are also not reported as <obj>.references when
producing heap snapshots.

Though the heapsnapshot's <class>.fields will contain entries
for unboxed fields, which causes the fields index calculation to be
incorrect.

This can cause various confusing things, e.g. incorrectly caluclated
retaining paths, since the <class>.fields.index doesn't match the
index in <obj>.references.

To fix this this CL will change the visiting code to emit dummy
references for unboxed fields.

The written test uncovered a few other issues:

  - report type_arguments and native_fields in <class>.fields
    => the visitors already visit those fields

  - fix `Class::next_{host,target}_field_offset` for classes
    with native fields
    => this will also shrink size of `NativeWrapperClass` subclasses

  - ensure classes with vm-defined layout are finalized
    => we assume objects should only exist in heap if their class
       is finalized

  - fix `FfiNativeFunction` type_argument offset

  - fixes for object fields list
    => add missing entries, fix existing entries

Fixes https://github.com/dart-lang/sdk/issues/49711

TEST=vm/dart{,_2}/heap_snapshot_regress_49711_test

Change-Id: I8e25680b2c0c8c49caafbb8da57b0b6419e89c4f
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/255814
Reviewed-by: Ryan Macnak <rmacnak@google.com>
Commit-Queue: Martin Kustermann <kustermann@google.com>
2022-08-23 05:17:49 +00:00

87 lines
2.3 KiB
C++

// Copyright (c) 2018, the Dart project authors. Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.
//
// This file (and "raw_object_fields.cc") provide a kind of reflection that
// allows us to identify the name of fields in hand-written "Raw..." classes
// (from "raw_object.h") given the class and the offset within the object. This
// is used for example by the snapshot profile writer ("v8_snapshot_writer.h")
// to show the property names of these built-in objects in the snapshot profile.
#ifndef RUNTIME_VM_RAW_OBJECT_FIELDS_H_
#define RUNTIME_VM_RAW_OBJECT_FIELDS_H_
#include <utility>
#include "vm/hash_map.h"
#include "vm/object.h"
#include "vm/raw_object.h"
namespace dart {
#if defined(DART_PRECOMPILER) || !defined(PRODUCT)
class OffsetsTable : public ZoneAllocated {
public:
explicit OffsetsTable(Zone* zone);
// Returns 'nullptr' if no offset was found.
// Otherwise, the returned string is allocated in global static memory.
const char* FieldNameForOffset(intptr_t cid, intptr_t offset);
struct OffsetsTableEntry {
intptr_t class_id;
const char* field_name;
bool is_compressed_pointer;
intptr_t offset;
};
static const MallocGrowableArray<OffsetsTableEntry>& offsets_table();
static void Init();
static void Cleanup();
private:
struct IntAndIntToStringMapTraits {
typedef std::pair<intptr_t, intptr_t> Key;
typedef const char* Value;
struct Pair {
Key key;
Value value;
Pair() : key({-1, -1}), value(nullptr) {}
Pair(Key k, Value v) : key(k), value(v) {}
};
static Value ValueOf(Pair pair) { return pair.value; }
static Key KeyOf(Pair pair) { return pair.key; }
static uword Hash(Key key) {
return Utils::WordHash(key.first ^ key.second);
}
static bool IsKeyEqual(Pair x, Key y) {
return x.key.first == y.first && x.key.second == y.second;
}
};
DirectChainedHashMap<IntAndIntToStringMapTraits> cached_offsets_;
};
#else
class OffsetsTable : public ZoneAllocated {
public:
explicit OffsetsTable(Zone* zone) {}
const char* FieldNameForOffset(intptr_t cid, intptr_t offset) {
return nullptr;
}
static void Init() {}
static void Cleanup() {}
};
#endif
} // namespace dart
#endif // RUNTIME_VM_RAW_OBJECT_FIELDS_H_