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Bug 716236 - Fix indentation in GuardObjects.h and allow its inclusion into C files; r=Waldo
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Ms2ger
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@ -38,125 +38,141 @@
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*
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* ***** END LICENSE BLOCK ***** */
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/* Implementation of macros to ensure correct use of RAII Auto* objects. */
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#ifndef mozilla_GuardObjects_h
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#define mozilla_GuardObjects_h
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#include "mozilla/Assertions.h"
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namespace mozilla {
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/**
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* The following classes are designed to cause assertions to detect
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* inadvertent use of guard objects as temporaries. In other words,
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* when we have a guard object whose only purpose is its constructor and
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* destructor (and is never otherwise referenced), the intended use
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* might be:
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* AutoRestore savePainting(mIsPainting);
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* but is is easy to accidentally write:
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* AutoRestore(mIsPainting);
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* which compiles just fine, but runs the destructor well before the
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* intended time.
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*
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* They work by adding (#ifdef DEBUG) an additional parameter to the
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* guard object's constructor, with a default value, so that users of
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* the guard object's API do not need to do anything. The default value
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* of this parameter is a temporary object. C++ (ISO/IEC 14882:1998),
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* section 12.2 [class.temporary], clauses 4 and 5 seem to assume a
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* guarantee that temporaries are destroyed in the reverse of their
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* construction order, but I actually can't find a statement that that
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* is true in the general case (beyond the two specific cases mentioned
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* there). However, it seems to be true.
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*
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* These classes are intended to be used only via the macros immediately
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* below them:
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* MOZ_DECL_USE_GUARD_OBJECT_NOTIFIER declares (ifdef DEBUG) a member
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* variable, and should be put where a declaration of a private
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* member variable would be placed.
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* MOZ_GUARD_OBJECT_NOTIFIER_PARAM should be placed at the end of the
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* parameters to each constructor of the guard object; it declares
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* (ifdef DEBUG) an additional parameter. (But use the *_ONLY_PARAM
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* variant for constructors that take no other parameters.)
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* MOZ_GUARD_OBJECT_NOTIFIER_PARAM_IN_IMPL should likewise be used in
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* the implementation of such constructors when they are not inline.
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* MOZ_GUARD_OBJECT_NOTIFIER_PARAM_TO_PARENT should be used in
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* the implementation of such constructors to pass the parameter to
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* a base class that also uses these macros
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* MOZ_GUARD_OBJECT_NOTIFIER_INIT is a statement that belongs in each
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* constructor. It uses the parameter declared by
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* MOZ_GUARD_OBJECT_NOTIFIER_PARAM.
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*
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* For more details, and examples of using these macros, see
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* https://developer.mozilla.org/en/Using_RAII_classes_in_Mozilla
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*/
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#ifdef __cplusplus
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#ifdef DEBUG
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class GuardObjectNotifier
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{
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namespace mozilla {
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namespace detail {
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/*
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* The following classes are designed to cause assertions to detect
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* inadvertent use of guard objects as temporaries. In other words,
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* when we have a guard object whose only purpose is its constructor and
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* destructor (and is never otherwise referenced), the intended use
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* might be:
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*
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* AutoRestore savePainting(mIsPainting);
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*
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* but is is easy to accidentally write:
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*
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* AutoRestore(mIsPainting);
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*
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* which compiles just fine, but runs the destructor well before the
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* intended time.
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*
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* They work by adding (#ifdef DEBUG) an additional parameter to the
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* guard object's constructor, with a default value, so that users of
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* the guard object's API do not need to do anything. The default value
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* of this parameter is a temporary object. C++ (ISO/IEC 14882:1998),
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* section 12.2 [class.temporary], clauses 4 and 5 seem to assume a
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* guarantee that temporaries are destroyed in the reverse of their
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* construction order, but I actually can't find a statement that that
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* is true in the general case (beyond the two specific cases mentioned
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* there). However, it seems to be true.
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*
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* These classes are intended to be used only via the macros immediately
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* below them:
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*
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* MOZ_DECL_USE_GUARD_OBJECT_NOTIFIER declares (ifdef DEBUG) a member
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* variable, and should be put where a declaration of a private
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* member variable would be placed.
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* MOZ_GUARD_OBJECT_NOTIFIER_PARAM should be placed at the end of the
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* parameters to each constructor of the guard object; it declares
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* (ifdef DEBUG) an additional parameter. (But use the *_ONLY_PARAM
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* variant for constructors that take no other parameters.)
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* MOZ_GUARD_OBJECT_NOTIFIER_PARAM_IN_IMPL should likewise be used in
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* the implementation of such constructors when they are not inline.
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* MOZ_GUARD_OBJECT_NOTIFIER_PARAM_TO_PARENT should be used in
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* the implementation of such constructors to pass the parameter to
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* a base class that also uses these macros
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* MOZ_GUARD_OBJECT_NOTIFIER_INIT is a statement that belongs in each
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* constructor. It uses the parameter declared by
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* MOZ_GUARD_OBJECT_NOTIFIER_PARAM.
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*
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* For more details, and examples of using these macros, see
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* https://developer.mozilla.org/en/Using_RAII_classes_in_Mozilla
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*/
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class GuardObjectNotifier
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{
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private:
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bool* mStatementDone;
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bool* statementDone;
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public:
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GuardObjectNotifier() : mStatementDone(NULL) {}
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GuardObjectNotifier() : statementDone(NULL) {}
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~GuardObjectNotifier() {
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*mStatementDone = true;
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*statementDone = true;
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}
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void SetStatementDone(bool *aStatementDone) {
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mStatementDone = aStatementDone;
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void setStatementDone(bool* statementIsDone) {
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statementDone = statementIsDone;
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}
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};
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};
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class GuardObjectNotificationReceiver
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{
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class GuardObjectNotificationReceiver
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{
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private:
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bool mStatementDone;
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bool statementDone;
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public:
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GuardObjectNotificationReceiver() : mStatementDone(false) {}
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GuardObjectNotificationReceiver() : statementDone(false) {}
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~GuardObjectNotificationReceiver() {
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/*
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* Assert that the guard object was not used as a temporary.
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* (Note that this assert might also fire if Init is not called
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* because the guard object's implementation is not using the
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* above macros correctly.)
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*/
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MOZ_ASSERT(mStatementDone);
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/*
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* Assert that the guard object was not used as a temporary.
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* (Note that this assert might also fire if init is not called
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* because the guard object's implementation is not using the
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* above macros correctly.)
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*/
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MOZ_ASSERT(statementDone);
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}
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void Init(const GuardObjectNotifier &aNotifier) {
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/*
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* aNotifier is passed as a const reference so that we can pass a
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* temporary, but we really intend it as non-const
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*/
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const_cast<GuardObjectNotifier&>(aNotifier).
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SetStatementDone(&mStatementDone);
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void init(const GuardObjectNotifier& constNotifier) {
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/*
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* constNotifier is passed as a const reference so that we can pass a
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* temporary, but we really intend it as non-const.
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*/
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GuardObjectNotifier& notifier = const_cast<GuardObjectNotifier&>(constNotifier);
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notifier.setStatementDone(&statementDone);
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}
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};
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};
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#define MOZ_DECL_USE_GUARD_OBJECT_NOTIFIER \
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mozilla::GuardObjectNotificationReceiver _mCheckNotUsedAsTemporary;
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#define MOZ_GUARD_OBJECT_NOTIFIER_PARAM \
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, const mozilla::GuardObjectNotifier& _notifier = \
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mozilla::GuardObjectNotifier()
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#define MOZ_GUARD_OBJECT_NOTIFIER_ONLY_PARAM \
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const mozilla::GuardObjectNotifier& _notifier = \
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mozilla::GuardObjectNotifier()
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#define MOZ_GUARD_OBJECT_NOTIFIER_PARAM_IN_IMPL \
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, const mozilla::GuardObjectNotifier& _notifier
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#define MOZ_GUARD_OBJECT_NOTIFIER_PARAM_TO_PARENT \
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, _notifier
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#define MOZ_GUARD_OBJECT_NOTIFIER_INIT \
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PR_BEGIN_MACRO _mCheckNotUsedAsTemporary.Init(_notifier); PR_END_MACRO
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} /* namespace detail */
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} /* namespace mozilla */
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#else /* defined(DEBUG) */
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#endif /* DEBUG */
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#define MOZ_DECL_USE_GUARD_OBJECT_NOTIFIER
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#define MOZ_GUARD_OBJECT_NOTIFIER_PARAM
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#define MOZ_GUARD_OBJECT_NOTIFIER_ONLY_PARAM
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#define MOZ_GUARD_OBJECT_NOTIFIER_PARAM_IN_IMPL
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#define MOZ_GUARD_OBJECT_NOTIFIER_PARAM_TO_PARENT
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#define MOZ_GUARD_OBJECT_NOTIFIER_INIT PR_BEGIN_MACRO PR_END_MACRO
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#ifdef DEBUG
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# define MOZ_DECL_USE_GUARD_OBJECT_NOTIFIER \
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mozilla::detail::GuardObjectNotificationReceiver _mCheckNotUsedAsTemporary;
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# define MOZ_GUARD_OBJECT_NOTIFIER_PARAM \
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, const mozilla::detail::GuardObjectNotifier& _notifier = \
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mozilla::detail::GuardObjectNotifier()
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# define MOZ_GUARD_OBJECT_NOTIFIER_ONLY_PARAM \
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const mozilla::detail::GuardObjectNotifier& _notifier = \
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mozilla::detail::GuardObjectNotifier()
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# define MOZ_GUARD_OBJECT_NOTIFIER_PARAM_IN_IMPL \
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, const mozilla::detail::GuardObjectNotifier& _notifier
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# define MOZ_GUARD_OBJECT_NOTIFIER_PARAM_TO_PARENT \
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, _notifier
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# define MOZ_GUARD_OBJECT_NOTIFIER_INIT \
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do { _mCheckNotUsedAsTemporary.init(_notifier); } while (0)
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#else
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# define MOZ_DECL_USE_GUARD_OBJECT_NOTIFIER
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# define MOZ_GUARD_OBJECT_NOTIFIER_PARAM
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# define MOZ_GUARD_OBJECT_NOTIFIER_ONLY_PARAM
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# define MOZ_GUARD_OBJECT_NOTIFIER_PARAM_IN_IMPL
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# define MOZ_GUARD_OBJECT_NOTIFIER_PARAM_TO_PARENT
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# define MOZ_GUARD_OBJECT_NOTIFIER_INIT do { } while (0)
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#endif
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#endif /* !defined(DEBUG) */
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} // namespace mozilla
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#endif /* __cplusplus */
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#endif /* mozilla_GuardObjects_h */
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