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Remove the name cache from QMetaType::typeName

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It was unnecessary, since we only cached the static types, which are all
generated by the macro anyway. The way it was implemented, this produced
data races that are strictly-speaking UB, even if all the threads were
writing the same values to the same data locations.

This commit changes a little the code to simplify, since we're changing
those lines anyway.

Task-number: QTBUG-58851
Change-Id: Idc5061f7145940f987dffffd14a30047846e3113
Reviewed-by: Marc Mutz <marc.mutz@kdab.com>
Reviewed-by: Olivier Goffart (Woboq GmbH) <ogoffart@woboq.com>
This commit is contained in:
Thiago Macieira 2017-02-13 16:36:49 -08:00
parent 7dff4b921b
commit fb376e0fcc
1 changed files with 14 additions and 25 deletions
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39
src/corelib/kernel/qmetatype.cpp
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@ -834,38 +834,27 @@ void QMetaType::registerStreamOperators(int idx, SaveOperator saveOp,
const char *QMetaType::typeName(int typeId)
{
const uint type = typeId;
// In theory it can be filled during compilation time, but for some reason template code
// that is able to do it causes GCC 4.6 to generate additional 3K of executable code. Probably
// it is not worth of it.
static const char *namesCache[QMetaType::HighestInternalId + 1];
const char *result;
if (type <= QMetaType::HighestInternalId && ((result = namesCache[type])))
return result;
#define QT_METATYPE_TYPEID_TYPENAME_CONVERTER(MetaTypeName, TypeId, RealName) \
case QMetaType::MetaTypeName: result = #RealName; break;
case QMetaType::MetaTypeName: return #RealName; break;
switch (QMetaType::Type(type)) {
QT_FOR_EACH_STATIC_TYPE(QT_METATYPE_TYPEID_TYPENAME_CONVERTER)
case QMetaType::UnknownType:
case QMetaType::User:
break;
}
default: {
if (Q_UNLIKELY(type < QMetaType::User)) {
return 0; // It can happen when someone cast int to QVariant::Type, we should not crash...
} else {
const QVector<QCustomTypeInfo> * const ct = customTypes();
QReadLocker locker(customTypesLock());
return ct && uint(ct->count()) > type - QMetaType::User && !ct->at(type - QMetaType::User).typeName.isEmpty()
? ct->at(type - QMetaType::User).typeName.constData()
: 0;
}
}
if (Q_UNLIKELY(type < QMetaType::User)) {
return nullptr; // It can happen when someone cast int to QVariant::Type, we should not crash...
}
const QVector<QCustomTypeInfo> * const ct = customTypes();
QReadLocker locker(customTypesLock());
return ct && uint(ct->count()) > type - QMetaType::User && !ct->at(type - QMetaType::User).typeName.isEmpty()
? ct->at(type - QMetaType::User).typeName.constData()
: nullptr;
#undef QT_METATYPE_TYPEID_TYPENAME_CONVERTER
Q_ASSERT(type <= QMetaType::HighestInternalId);
namesCache[type] = result;
return result;
}
/*