On Thursday 8 August 2024 11:22:39 GMT-7 Thiago Macieira wrote: > My solution is to have moc parse a new declaration Q_DECLARE_FLAGS64, which > indicates the flag is 64-bit, and then generate different data. I have not > implemented Q_FLAGS64 or Q_ENUM64 yet.
An alternative solution I am looking into right now is to move the integer
array generation to C++ constexpr functions, like we did for the string array.
In those functions, we can know that the enumeration is 64-bit wide and then
generate the extra fields without having to have moc understand that they are
64-bit. In theory this will work, but in practice we need to test the multiple
compilers extensively to know if we won't overflow limitations in constexpr-
time execution or just plain compiler bugs (MSVC fails with [1] for example
and generates bad code). The moc output would look something like:
static constexpr std::array qt_meta_data_CLASSUserClassENDCLASS =
QtMocHelpers::uintData()
.addClassInfo(1, 3)
.addClassInfo(4, 5)
.addMethod(6, 2, 0x06, { QMetaType::Void, 0x80000000 | 17, 8 })
.addMethod(7, 2, 0x06, { QMetaType::Void, 0x80000000 | 9, 8 })
.addMethod(8, 2, 0x0a, { QMetaType::Void })
.addEnum(10, 10, 0x00, { 11, 12 }, { UserClass::V0, UserClass::V1 })
.addEnum(13, 14, 0x01, { 15, 16 }, { UserClass::F0, UserClass::F1 })
.generate(/* revision */ 12, /* flags */ 0);
There's no guarantee this will work, and especially that it will for C++17,
though I wouldn't mind declaring you must use C++20 to access 64-bit
enumerators.
If this works, we get the best of both worlds: all 64-bit enumerations and
flags automatically get their high part stored without impacting the existing
32-bit ones, and moc doesn't need to know that they are 64-bit.
Long-term, we should generate the char, integer and metatype arrays in a
single call, so it can be used with C++ reflection. I have a hard time figuring
out how that can be accomplished even without it.
[1] https://codereview.qt-project.org/c/qt/qtbase/+/537384
--
Thiago Macieira - thiago.macieira (AT) intel.com
Principal Engineer - Intel DCAI Platform & System Engineering
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