QMetaType: remember whether a type was registered with Q_DECLARE_METATYPE

There are two ways to register a type: using Q_DECLARE_METATYPE(T) and
using qRegisterMetaType<T>("T"). Doing one thing in one translation
unit and another thing in another TU constitutes an ODR violation,
because the value of QMetaTypeId<T>::Defined will differ in the two
TUs.

By adding the information whether a type was declared with
Q_DECLARE_METATYPE to the typeFlags(), such a use will trigger
the existing binary-incompatibility failure that checks for
equality of the incoming type flags with the stored ones (if any).

I had to encode the type as a defaulted function argument in order
to avoid the linker merging instantiations of the function templates
and therefore rendering the detection moot.

Change-Id: I82017caf300458b411cc8ac2f6653536fac64117
Reviewed-by: Lars Knoll <lars.knoll@digia.com>

1 files changed, 5 insertions, 0 deletions

diff --git a/tests/manual/qmetatype/qmetatype.pro b/tests/manual/qmetatype/qmetatype.pro
new file mode 100644
index 0000000000..a4f941e577
--- /dev/null
+++ b/tests/manual/qmetatype/qmetatype.pro
@@ -0,0 +1,5 @@
+CONFIG += testcase
+TARGET = tst_qmetatype_expect_fail
+QT = core
+HEADERS = declare_metatype_noninline.h
+SOURCES = tst_qmetatype.cpp declare_metatype_noninline.cpp