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JNI: simplify implementation of native function wrappers

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When declaring native callback functions with the JNI type system, then
we actually register a helper function with variadic arguments, and
implement that to forward the arguments to the declared function, which
then might use higher-level types as arguments. We deduce those
higher-level types through a variadic template, and use std::tuple as
well as std::apply to generate the calls.

Simplify the implementation by using std::make_tuple, and replace
q20:remove_cvref_t with std::decay_t; this is what std::make_tuple uses,
and we don't need to maintain functions and arrays as such.

Found during 6.7 header review.

Task-number: QTBUG-119952
Change-Id: I7cd206c6b372c2ec62a10feb5f9253f5607f01a9
Reviewed-by: Marc Mutz <marc.mutz@qt.io>
(cherry picked from commit 76cf922980cf0cde7cb03f4bec8f17eab94a5767)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>
This commit is contained in:
Volker Hilsheimer 2024-01-30 15:19:23 +01:00 committed by Qt Cherry-pick Bot
parent e20f2a6c8b
commit db5e112419
1 changed files with 3 additions and 5 deletions
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8
src/corelib/kernel/qjnitypes.h
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@ -96,20 +96,18 @@ struct JNITypeForArgImpl<QString>
}; };
template <typename Arg> template <typename Arg>
using JNITypeForArg = typename JNITypeForArgImpl<q20::remove_cvref_t<Arg>>::Type; using JNITypeForArg = typename JNITypeForArgImpl<std::decay_t<Arg>>::Type;
template <typename Arg, typename Type> template <typename Arg, typename Type>
static inline auto methodArgFromVarArg(Type &&t) static inline auto methodArgFromVarArg(Type &&t)
{ {
return JNITypeForArgImpl<q20::remove_cvref_t<Arg>>::fromVarArg(std::move(t)); return JNITypeForArgImpl<std::decay_t<Arg>>::fromVarArg(std::move(t));
} }
// Turn a va_list into a tuple of typed arguments // Turn a va_list into a tuple of typed arguments
template <typename ...Args> template <typename ...Args>
static constexpr auto makeTupleFromArgsHelper(va_list args) static constexpr auto makeTupleFromArgsHelper(va_list args)
{ {
return std::tuple<q20::remove_cvref_t<Args>...>{ return std::tuple(methodArgFromVarArg<Args>(va_arg(args, JNITypeForArg<Args>))...);
methodArgFromVarArg<q20::remove_cvref_t<Args>>(va_arg(args, JNITypeForArg<Args>))...
};
} }
template <typename Ret, typename ...Args> template <typename Ret, typename ...Args>