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53 lines
1.9 KiB
C++
53 lines
1.9 KiB
C++
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
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* vim: set ts=8 sts=4 et sw=4 tw=99:
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* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#ifndef js_TraceKind_h
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#define js_TraceKind_h
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namespace JS {
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// When tracing a thing, the GC needs to know about the layout of the object it
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// is looking at. There are a fixed number of different layouts that the GC
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// knows about. The "trace kind" is a static map which tells which layout a GC
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// thing has.
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//
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// Although this map is public, the details are completely hidden. Not all of
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// the matching C++ types are exposed, and those that are, are opaque.
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//
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// See Value::gcKind() and JSTraceCallback in Tracer.h for more details.
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enum class TraceKind
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{
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// These trace kinds have a publicly exposed, although opaque, C++ type.
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// Note: The order here is determined by our Value packing. Other users
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// should sort alphabetically, for consistency.
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Object = 0x00,
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String = 0x01,
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Symbol = 0x02,
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Script = 0x03,
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// Shape details are exposed through JS_TraceShapeCycleCollectorChildren.
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Shape = 0x04,
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// ObjectGroup details are exposed through JS_TraceObjectGroupCycleCollectorChildren.
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ObjectGroup = 0x05,
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// The kind associated with a nullptr.
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Null = 0x06,
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// The following kinds do not have an exposed C++ idiom.
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BaseShape = 0x0F,
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JitCode = 0x1F,
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LazyScript = 0x2F
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};
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const static uintptr_t OutOfLineTraceKindMask = 0x07;
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static_assert(uintptr_t(JS::TraceKind::BaseShape) & OutOfLineTraceKindMask, "mask bits are set");
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static_assert(uintptr_t(JS::TraceKind::JitCode) & OutOfLineTraceKindMask, "mask bits are set");
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static_assert(uintptr_t(JS::TraceKind::LazyScript) & OutOfLineTraceKindMask, "mask bits are set");
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} // namespace JS
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#endif // js_TraceKind_h
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