JSAPI 38 で廃止
この機能は廃止されました。まだいくつかのブラウザーで動作するかもしれませんが、いつ削除されてもおかしくないので、使わないようにしましょう。
この記事は SpiderMonkey 1.8 の新機能について書かれています。
DEBUG のみ。ヒープに割り当てられたもののオブジェクトグラフをダンプします。構文
bool
JS_DumpHeap(JSRuntime *rt, FILE *fp, void* startThing, JSGCTraceKind kind,
void *thingToFind, size_t maxDepth, void *thingToIgnore);
| Name | Type | Description |
|---|---|---|
cx |
JSContext * |
Pointer to a JS context. Every JSContext is permanently associated with a JSRuntime; each JSRuntime contains a GC heap. |
fp |
FILE * |
File for the dump output. |
startThing |
void * |
NULL or a pointer to a GC thing (use JS::Value::toGCThing() to obtain a pointer to pass here). When null, dump all things reachable from the runtime roots. When non-null, dump only things reachable from the object indicated. |
startKind |
JSGCTraceKind |
Trace kind of startThing, if startThing is not null. Must be JSTRACE_OBJECT when startThing is null. |
thingToFind |
void * |
NULL or a pointer to a GC thing. If this is non-null, JS_DumpHeap only dumps paths in the object graph leading to the specified thing. |
maxDepth |
size_t |
The upper bound on the number of edges to descend from the graph roots. |
thingToIgnore |
void * |
NULL or a pointer to a GC thing that will be ignored during graph traversal. |
enum JSGCTraceKind
{
// These trace kinds have a publicly exposed, although opaque, C++ type.
// Note: The order here is determined by our Value packing. Other users
// should sort alphabetically, for consistency.
JSTRACE_OBJECT = 0x00,
JSTRACE_STRING = 0x01,
JSTRACE_SYMBOL = 0x02,
JSTRACE_SCRIPT = 0x03,
// Shape details are exposed through JS_TraceShapeCycleCollectorChildren.
JSTRACE_SHAPE = 0x04,
// The kind associated with a nullptr.
JSTRACE_NULL = 0x06,
// A kind that indicates the real kind should be looked up in the arena.
JSTRACE_OUTOFLINE = 0x07,
// The following kinds do not have an exposed C++ idiom.
JSTRACE_BASE_SHAPE = 0x0F,
JSTRACE_JITCODE = 0x1F,
JSTRACE_LAZY_SCRIPT = 0x2F,
JSTRACE_TYPE_OBJECT = 0x3F,
JSTRACE_LAST = JSTRACE_TYPE_OBJECT
};
Description
See バグ 378261 for detail.
When tracing a thing, the GC needs to know about the layout of the object it is looking at. There are a fixed number of different layouts that the GC knows about. The "trace kind" is a static map which tells which layout a GC thing has.
Although this map is public, the details are completely hidden. Not all of the matching C++ types are exposed, and those that are, are opaque.
See JS::Value::gcKind() and JSTraceCallback in <codde>Tracer.h</codde> for more details.