QVariant: attempt to work around an ICE on linux-arm-gnueabi-g++ (Ubuntu 11.10) with constexpr QSizePolicy

This is the error:

  src/corelib/kernel/qvariant_p.h: In constructor ‘QVariantPrivateSharedEx<T>::QVariantPrivateSharedEx() [with T = QSizePolicy]’:
  src/corelib/kernel/qvariant_p.h:107:61: internal compiler error: in gimplify_init_ctor_eval, at gimplify.c:3560

There are two things fishy in this file:

1. Use of the unnamed namespace in a file that gets included
   in different libraries. While not technically undefined
   behavior, it may become so when used in the implementation,
   which it is.
2. Missing explicit initialization of a member of
   QVariantPrivateSharedEx. This is just a wild guess, because
   the ICE happens in that line. That class itself is quite
   smelly, because the address of an object is taken before
   the lifetime of the object begins. A fix would be to store
   the object in a wrapper class from which QVPSEx inherits
   _first_, but then a cast from QVPSEx to QVariant::PrivateShared
   would require pointer adjustments, and I didn't look through
   all the code to determine whether that would be an issue.
   Having been bitten by this sometime ago:
    https://marcmutz.wordpress.com/private-practice/private-practice-taming-templates/#edit-20111128
   I opted to do these easy changes first to see whether they
   already fix the ICE.

Change-Id: Ic15fd928b3dff2318c425c915b2dab5e54254d71
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

1 files changed, 1 insertions, 3 deletions

diff --git a/src/corelib/kernel/qvariant_p.h b/src/corelib/kernel/qvariant_p.h
index 9b9e266f8e..9e4f468872 100644
--- a/src/corelib/kernel/qvariant_p.h
+++ b/src/corelib/kernel/qvariant_p.h
@@ -54,7 +54,6 @@
 
 QT_BEGIN_NAMESPACE
 
-namespace {
 template<typename T>
 struct QVariantIntegrator
 {
@@ -64,7 +63,6 @@ struct QVariantIntegrator
 Q_STATIC_ASSERT(QVariantIntegrator<double>::CanUseInternalSpace);
 Q_STATIC_ASSERT(QVariantIntegrator<long int>::CanUseInternalSpace);
 Q_STATIC_ASSERT(QVariantIntegrator<qulonglong>::CanUseInternalSpace);
-} // namespace
 
 #ifdef Q_CC_SUN // Sun CC picks the wrong overload, so introduce awful hack
 
@@ -104,7 +102,7 @@ inline T *v_cast(QVariant::Private *d, T * = 0)
 template <class T> class QVariantPrivateSharedEx : public QVariant::PrivateShared
 {
 public:
-    QVariantPrivateSharedEx() : QVariant::PrivateShared(&m_t) { }
+    QVariantPrivateSharedEx() : QVariant::PrivateShared(&m_t), m_t() { }
     QVariantPrivateSharedEx(const T&t) : QVariant::PrivateShared(&m_t), m_t(t) { }
 
 private: