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JS_DumpHeap 编辑

Obsolete since JSAPI 38
This feature is obsolete. Although it may still work in some browsers, its use is discouraged since it could be removed at any time. Try to avoid using it.

This article covers features introduced in SpiderMonkey 1.8

DEBUG only. Dump the object graph of heap-allocated things.

Syntax

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
};

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.

JS_DumpHeap 编辑

Syntax

Description

See Also

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友情链接

JS_DumpHeap 编辑

Syntax

Description

See Also

如果你对这篇内容有疑问，欢迎到本站社区发帖提问 参与讨论，获取更多帮助，或者扫码二维码加入 Web 技术交流群。

发布评论

词条统计

友情链接

如果你对这篇内容有疑问，欢迎到本站社区发帖提问参与讨论，获取更多帮助，或者扫码二维码加入 Web 技术交流群。