Here are the notes from the session
https://wiki.qt.io/Qt_Contributors_Summit_2019_-_moc_and_QMetaObject
Summary:
We discuss if we should rewrite moc using libclang.
moc currently hasn't still fully be ported to support C++11 yet. Features such
as raw literals, trailing returns and other will confuse moc.
It is agreed that using clang for moc would be the path forward even if it is
slower. We discussed that we should use the clang C API for compatibility
reasons. we should avoid using Qt in the implementation to simplify the
bootstrap proccess.
There is already a prototype i made years ago (but it is using the C++ API)
https://github.com/woboq/moc-ng
However this was not seen as a blocking issue for Qt6 as the changes we want to
do to the "generator" can easily be ported to the new moc without requiring to
do all the work twice..
We discussed if Qt should provide an additional API such as
https://github.com/woboq/verdigris which allow to write code that does not use
moc. But the consensus is that this wasn't usefull, and that verdigris can stay
a separate library. However it should still be made possible. (And a solution
for the new json output required by QML3 will be needed)
We discussed the reflexion features coming in future version of C++. But since
this is for the far future and won't help us immediately, we won't consider
them now. Later they can be adopted.
The QMetaObject itself will gain new feature for performance reasons so QML can
be faster.
--
Olivier
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