Qt Contributors Summit 2019 - moc and QMetaObject: Difference between revisions
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Milian Wolff (talk | contribs) No edit summary |
Milian Wolff (talk | contribs) No edit summary |
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*** we only need to parse a few things correctly, but we have to ignore all of the rest properly, which is tough | *** we only need to parse a few things correctly, but we have to ignore all of the rest properly, which is tough | ||
** for qt6 we could remove old system to use moc without passing include paths, i.e. hard error if file is missing | ** for qt6 we could remove old system to use moc without passing include paths, i.e. hard error if file is missing | ||
* one could add a clang plugin in addition if moc is also "partially" a library that could be reused from elsewhere | |||
** that would allow us to do moc'ing at compile time to remove any overhead | |||
** we will get that once refactoring support lands in C++ for real | |||
* when we need to extend moc, do we extend the old one or do we build a new tool based on top of libclang and add the new features there? | * when we need to extend moc, do we extend the old one or do we build a new tool based on top of libclang and add the new features there? | ||
** who does the work? | |||
** do we need it in Qt 6? |
Revision as of 12:46, 21 November 2019
- breaking ABI allows for performance changes and additional features in QMetaObject
- what about newer C++ features
- raw literals are an issue e.g. like in tests
- worse, error handling is confusing and makes it hard for users to know what's going on
- can we use libclang instead of workarounds? see moc-ng
- libclang can be quite slow, but we already did it for lupdate and qdoc
- roughly an order of magnitude slower, but we could do better? => this is the biggest issue probably
- when using build farms, moc is a bottleneck - unless it could be distributed but that doesn't sound feasible
- bootstrapping is quasi impossible when using libclang, we'd have to port moc to not use C++ anymore
- size of libclang + dependencies is only an issue for developer machines, roughly ~80mb
- windows headers should be supported nowadays
- libclang C api can be used, C++ api isn't stable, not a good idea probably - need to stay compatible with trunk continuously otherwise
- why can't we use something easier than libclang?
- parsing C++ is actually very hard with some C++ changes recently
- we only need to parse a few things correctly, but we have to ignore all of the rest properly, which is tough
- for qt6 we could remove old system to use moc without passing include paths, i.e. hard error if file is missing
- raw literals are an issue e.g. like in tests
- one could add a clang plugin in addition if moc is also "partially" a library that could be reused from elsewhere
- that would allow us to do moc'ing at compile time to remove any overhead
- we will get that once refactoring support lands in C++ for real
- when we need to extend moc, do we extend the old one or do we build a new tool based on top of libclang and add the new features there?
- who does the work?
- do we need it in Qt 6?