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// Copyright 2014 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef TOOLS_BLINK_GC_PLUGIN_TRACING_STATUS_H_
#define TOOLS_BLINK_GC_PLUGIN_TRACING_STATUS_H_
// TracingStatus is a four-point value ordered by
// illegal < unneeded < unknown < needed
//
// It is used to categorize tracing of fields:
//
// * illegal field is invalid/illegal to trace.
// * unneeded field has type with no traceable fields of its own;
// it may have an empty trace() method. Not harmful
// to trace, but not needed.
// * unknown initial TracingStatus value.
// * needed field is a heap reference or an object containing
// traceable fields.
//
// Tracing status |illegal| is considered an error; treating |unneeded| also
// as an error would detect and report unnecessary tracing of objects that
// probably don't need to be on the Blink GC heap. However, template use
// and instantiation can leave us with classes that do have empty trace
// methods and no traceable fields -- reporting these as errors/warnings
// wouldn't work. Hence, only consider |illegal| as an error TracingStatus
// state.
class TracingStatus {
public:
static TracingStatus Illegal() { return kIllegal; }
static TracingStatus Unneeded() { return kUnneeded; }
static TracingStatus Unknown() { return kUnknown; }
static TracingStatus Needed() { return kNeeded; }
bool IsIllegal() const { return status_ == kIllegal; }
bool IsUnneeded() const { return status_ == kUnneeded; }
bool IsUnknown() const { return status_ == kUnknown; }
bool IsNeeded() const { return status_ == kNeeded; }
TracingStatus LUB(const TracingStatus& other) const {
return status_ > other.status_ ? status_ : other.status_;
}
bool operator==(const TracingStatus& other) const {
return status_ == other.status_;
}
private:
enum Status { kIllegal, kUnneeded, kUnknown, kNeeded };
TracingStatus(Status status) : status_(status) {}
Status status_;
};
#endif // TOOLS_BLINK_GC_PLUGIN_TRACING_STATUS_H_
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