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[embind] Use std::disjunction for checking policy arguments. #22603

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merged 1 commit into from
Sep 20, 2024
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[embind] Use std::disjunction for checking policy arguments. #22603

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67 changes: 23 additions & 44 deletions system/include/emscripten/bind.h
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Original file line number Diff line number Diff line change
Expand Up @@ -359,6 +359,27 @@ struct reference : public allow_raw_pointers {};

namespace internal {

#if __cplusplus >= 201703L
template <typename... Args> using conjunction = std::conjunction<Args...>;
template <typename... Args> using disjunction = std::disjunction<Args...>;
#else
// Helper available in C++14.
template <bool _Test, class _T1, class _T2>
using conditional_t = typename std::conditional<_Test, _T1, _T2>::type;

template<class...> struct conjunction : std::true_type {};
template<class B1> struct conjunction<B1> : B1 {};
template<class B1, class... Bn>
struct conjunction<B1, Bn...>
: conditional_t<bool(B1::value), conjunction<Bn...>, B1> {};

template<class...> struct disjunction : std::false_type {};
template<class B1> struct disjunction<B1> : B1 {};
template<class B1, class... Bn>
struct disjunction<B1, Bn...>
: conditional_t<bool(B1::value), disjunction<Bn...>, B1> {};
#endif

template<typename... Policies>
struct isPolicy;

Expand Down Expand Up @@ -428,40 +449,10 @@ struct GetReturnValuePolicy<ReturnType, T, Rest...> {
};

template<typename... Policies>
struct isAsync;

template<typename... Rest>
struct isAsync<async, Rest...> {
static constexpr bool value = true;
};

template<typename T, typename... Rest>
struct isAsync<T, Rest...> {
static constexpr bool value = isAsync<Rest...>::value;
};

template<>
struct isAsync<> {
static constexpr bool value = false;
};
using isAsync = disjunction<std::is_same<async, Policies>...>;

template<typename... Policies>
struct isNonnullReturn;

template<typename... Rest>
struct isNonnullReturn<nonnull<ret_val>, Rest...> {
static constexpr bool value = true;
};

template<typename T, typename... Rest>
struct isNonnullReturn<T, Rest...> {
static constexpr bool value = isNonnullReturn<Rest...>::value;
};

template<>
struct isNonnullReturn<> {
static constexpr bool value = false;
};
using isNonnullReturn = disjunction<std::is_same<nonnull<ret_val>, Policies>...>;
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Nice!

What are async and non_null in the above lines by the way? Are they special values defines somewhere, or just some kind of placeholder?

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Policy args are basically options you can pass into function bindings. e.g.

   function('sleep', &sleep, async());
   function('constructor', &constructor, nonnull<ret_val>());


}

Expand Down Expand Up @@ -985,18 +976,6 @@ struct SetterPolicy<PropertyTag<Setter, SetterArgumentType>> {
}
};

// Helper available in C++14.
template <bool _Test, class _T1, class _T2>
using conditional_t = typename std::conditional<_Test, _T1, _T2>::type;

// Conjunction is available in C++17
template<class...> struct conjunction : std::true_type {};
template<class B1> struct conjunction<B1> : B1 {};
template<class B1, class... Bn>
struct conjunction<B1, Bn...>
: conditional_t<bool(B1::value), conjunction<Bn...>, B1> {};


class noncopyable {
protected:
noncopyable() {}
Expand Down
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