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QVariant: don't leak PrivateShared if the constructor throws 

This means we can't do a tail-call from customConstruct when
PrivateShared is in use. But the case without that is still a tail-call.

Change-Id: I3859764fed084846bcb0fffd17045d144181ea84
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>
bb10
Thiago Macieira 2022-07-22 22:08:24 -07:00
parent 0db329e48d
commit 392e445393
1 changed files with 22 additions and 9 deletions
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31
src/corelib/kernel/qvariant.cpp
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@ -235,6 +235,21 @@ static bool isValidMetaTypeForVariant(const QtPrivate::QMetaTypeInterface *iface
return true;
}
template <typename F> static QVariant::PrivateShared *
customConstructShared(const QtPrivate::QMetaTypeInterface *iface, F &&construct)
{
struct Deleter {
void operator()(QVariant::PrivateShared *p) const
{ QVariant::PrivateShared::free(p); }
};
// this is exception-safe
std::unique_ptr<QVariant::PrivateShared, Deleter> ptr;
ptr.reset(QVariant::PrivateShared::create(iface));
construct(ptr->data());
return ptr.release();
}
// the type of d has already been set, but other field are not set
static void customConstruct(const QtPrivate::QMetaTypeInterface *iface, QVariant::Private *d,
const void *copy)
@ -252,20 +267,17 @@ static void customConstruct(const QtPrivate::QMetaTypeInterface *iface, QVariant
// ### Qt 7: remove nullptr_t special casing
d->is_null = !copy QT6_ONLY(|| isInterfaceFor<std::nullptr_t>(iface));
void *dst;
if (QVariant::Private::canUseInternalSpace(iface)) {
d->is_shared = false;
dst = &d->data;
if (!copy && !iface->defaultCtr)
return; // trivial default constructor, we've already memset
construct(iface, d->data.data, copy);
} else {
d->data.shared = QVariant::PrivateShared::create(iface);
d->data.shared = customConstructShared(iface, [=](void *where) {
construct(iface, where, copy);
});
d->is_shared = true;
dst = d->data.shared->data();
}
// now ask QMetaType to construct for us
construct(iface, dst, copy);
}
static void customClear(QVariant::Private *d)
@ -350,8 +362,9 @@ QVariant::Private::Private(std::piecewise_construct_t, const T &t)
new (data.data) T(t);
} else {
static_assert(!isNothrowQVariantConstructible); // we allocate memory, even if T doesn't
data.shared = QVariant::PrivateShared::create(QtPrivate::qMetaTypeInterfaceForType<T>());
new (data.shared->data()) T(t);
data.shared = customConstructShared(iface, [=](void *where) {
new (where) T(t);
});
}
}