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+// file : build2/function.hxx -*- C++ -*-
+// copyright : Copyright (c) 2014-2017 Code Synthesis Ltd
+// license : MIT; see accompanying LICENSE file
+
+#ifndef BUILD2_FUNCTION_HXX
+#define BUILD2_FUNCTION_HXX
+
+#include <utility> // index_sequence
+#include <type_traits> // aligned_storage
+#include <unordered_map>
+
+#include <build2/types.hxx>
+#include <build2/utility.hxx>
+
+#include <build2/variable.hxx>
+#include <build2/diagnostics.hxx>
+
+namespace build2
+{
+ // Functions can be overloaded based on types of their arguments but
+ // arguments can be untyped and a function can elect to accept an argument
+ // of any type.
+ //
+ // Functions can be qualified (e.g, string.length(), path.directory()) and
+ // unqualified (e.g., length(), directory()). Only functions overloaded on
+ // static types can be unqualified plus they should also define a qualified
+ // alias.
+ //
+ // Low-level function implementation would be called with a list of values
+ // as arguments. There is also higher-level, more convenient support for
+ // defining functions as pointers to functions (including capture-less
+ // lambdas), pointers to member functions (e.g., string::size()), or
+ // pointers to data members (e.g., name::type). In this case the build2
+ // function types are automatically matched to C++ function types according
+ // to these rules:
+ //
+ // T - statically-typed (value_traits<T> must be defined)
+ // names - untyped
+ // value - any type
+ // T* - NULL-able argument (here T can be names)
+ // value* - NULL-able any type (never NULL itself, use value::null)
+ // optional<T> - optional argument (here T can be T*, names, value)
+ //
+ // Optional arguments must be last. In case of a failure the function is
+ // expected to issue diagnostics and throw failed. Note that the arguments
+ // are conceptually "moved" and can be reused by the implementation.
+ //
+ // Normally functions come in families that share a common qualification
+ // (e.g., string. or path.). The function_family class is a "registrar"
+ // that simplifies handling of function families. For example:
+ //
+ // function_family f ("string");
+ //
+ // // Register length() and string.length().
+ // //
+ // f["length"] = &string::size;
+ //
+ // // Register string.max_size().
+ // //
+ // f[".max_size"] = []() {return string ().max_size ();};
+ //
+ // For more examples/ideas, study the existing function families (reside
+ // in the functions-*.cxx files).
+ //
+ struct function_overload;
+
+ using function_impl = value (vector_view<value>, const function_overload&);
+
+ struct function_overload
+ {
+ const char* name; // Set to point to key by insert() below.
+ const char* alt_name; // Alternative name, NULL if none. This is the
+ // qualified name for unqualified or vice verse.
+
+ // Arguments.
+ //
+ // A function can have a number of optional arguments. Arguments can also
+ // be typed. A non-existent entry in arg_types means a value of any type.
+ // A NULL entry means an untyped value.
+ //
+ // If arg_max equals to arg_variadic, then the function takes an unlimited
+ // number of arguments. In this case the semantics of arg_min and
+ // arg_types is unchanged.
+ //
+ static const size_t arg_variadic = size_t (~0);
+
+ using types = vector_view<const optional<const value_type*>>;
+
+ const size_t arg_min;
+ const size_t arg_max;
+ const types arg_types;
+
+ // Function implementation.
+ //
+ function_impl* const impl;
+
+ // Auxiliary data storage. Note that it is assumed to be POD (no
+ // destructors, bitwise copy, etc).
+ //
+ std::aligned_storage<sizeof (void*) * 3>::type data;
+ static const size_t data_size = sizeof (decltype (data));
+
+ function_overload () = default;
+
+ function_overload (const char* an,
+ size_t mi, size_t ma, types ts,
+ function_impl* im)
+ : alt_name (an),
+ arg_min (mi), arg_max (ma), arg_types (move (ts)),
+ impl (im) {}
+
+ template <typename D>
+ function_overload (const char* an,
+ size_t mi, size_t ma, types ts,
+ function_impl* im,
+ D d)
+ : function_overload (an, mi, ma, move (ts), im)
+ {
+ // std::is_pod appears to be broken in VC15 and also in GCC up to
+ // 5 (pointers to members).
+ //
+#if !((defined(_MSC_VER) && _MSC_VER <= 1910) || \
+ (defined(__GNUC__) && !defined(__clang__) && __GNUC__ <= 5))
+ static_assert (std::is_pod<D>::value, "type is not POD");
+#endif
+ static_assert (sizeof (D) <= data_size, "insufficient space");
+ new (&data) D (move (d));
+ }
+ };
+
+ ostream&
+ operator<< (ostream&, const function_overload&); // Print signature.
+
+ class function_map
+ {
+ public:
+ using map_type = std::unordered_multimap<string, function_overload>;
+ using iterator = map_type::iterator;
+ using const_iterator = map_type::const_iterator;
+
+ iterator
+ insert (string name, function_overload);
+
+ void
+ erase (iterator i) {map_.erase (i);}
+
+ value
+ call (const string& name, vector_view<value> args, const location& l) const
+ {
+ return call (name, args, l, true).first;
+ }
+
+ // As above but do not fail if no match was found (but still do if the
+ // match is ambiguous). Instead return an indication of whether the call
+ // was made. Used to issue custom diagnostics when calling internal
+ // functions.
+ //
+ pair<value, bool>
+ try_call (const string& name,
+ vector_view<value> args,
+ const location& l) const
+ {
+ return call (name, args, l, false);
+ }
+
+ iterator
+ begin () {return map_.begin ();}
+
+ iterator
+ end () {return map_.end ();}
+
+ const_iterator
+ begin () const {return map_.begin ();}
+
+ const_iterator
+ end () const {return map_.end ();}
+
+ private:
+ pair<value, bool>
+ call (const string&, vector_view<value>, const location&, bool fail) const;
+
+ map_type map_;
+ };
+
+ extern function_map functions;
+
+ class function_family
+ {
+ public:
+ // The default thunk catches invalid_argument and issues diagnostics
+ // by assuming it is related to function arguments and contains useful
+ // description.
+ //
+ // In order to implement a custom thunk (e.g., to catch additional extra
+ // exceptions), you would normally call the default implementation.
+ //
+ static value
+ default_thunk (vector_view<value>, const function_overload&);
+
+ // A function family uses a common qualification (though you can pass
+ // empty string to supress it). For an unqualified name (doesn't not
+ // contain a dot) the qualified version is added automatically. A name
+ // containing a leading dot is a shortcut notation for a qualified-only
+ // name.
+ //
+ explicit
+ function_family (string qual, function_impl* thunk = &default_thunk)
+ : qual_ (qual), thunk_ (thunk) {}
+
+ struct entry;
+
+ entry
+ operator[] (string name) const;
+
+ private:
+ const string qual_;
+ function_impl* thunk_;
+ };
+
+ // Implementation details. If you can understand and explain all of this,
+ // then you are hired ;-)!
+ //
+
+ template <typename T>
+ struct function_arg
+ {
+ static const bool null = false;
+ static const bool opt = false;
+
+ static constexpr optional<const value_type*>
+ type () {return &value_traits<T>::value_type;}
+
+ static T&&
+ cast (value* v)
+ {
+ if (v->null)
+ throw invalid_argument ("null value");
+
+ // Use fast but unchecked cast since the caller matched the types.
+ //
+ return move (v->as<T> ());
+ }
+ };
+
+ template <>
+ struct function_arg<names> // Untyped.
+ {
+ static const bool null = false;
+ static const bool opt = false;
+
+ static constexpr optional<const value_type*>
+ type () {return nullptr;}
+
+ static names&&
+ cast (value* v)
+ {
+ if (v->null)
+ throw invalid_argument ("null value");
+
+ return move (v->as<names> ());
+ }
+ };
+
+ template <>
+ struct function_arg<value> // Anytyped.
+ {
+ static const bool null = false;
+ static const bool opt = false;
+
+ static constexpr optional<const value_type*>
+ type () {return nullopt;}
+
+ static value&&
+ cast (value* v)
+ {
+ if (v->null)
+ throw invalid_argument ("null value");
+
+ return move (*v);
+ }
+ };
+
+ template <typename T>
+ struct function_arg<T*>: function_arg<T>
+ {
+ static const bool null = true;
+
+ static T*
+ cast (value* v)
+ {
+ if (v->null)
+ return nullptr;
+
+ // This looks bizarre but makes sense. The cast() that we are calling
+ // returns an r-value reference to (what's inside) v. And it has to
+ // return an r-value reference to that the value is moved into by-value
+ // arguments.
+ //
+ T&& r (function_arg<T>::cast (v));
+ return &r;
+ }
+ };
+
+ template <>
+ struct function_arg<value*>: function_arg<value>
+ {
+ static const bool null = true;
+
+ static value*
+ cast (value* v) {return v;} // NULL indicator in value::null.
+ };
+
+ template <typename T>
+ struct function_arg<optional<T>>: function_arg<T>
+ {
+ static const bool opt = true;
+
+ static optional<T>
+ cast (value* v)
+ {
+ return v != nullptr ? optional<T> (function_arg<T>::cast (v)) : nullopt;
+ }
+ };
+
+ // Number of optional arguments. Note that we currently don't check that
+ // they are all at the end.
+ //
+ template <typename A0, typename... A>
+ struct function_args_opt
+ {
+ static const size_t count = (function_arg<A0>::opt ? 1 : 0) +
+ function_args_opt<A...>::count;
+ };
+
+ template <typename A0>
+ struct function_args_opt<A0>
+ {
+ static const size_t count = (function_arg<A0>::opt ? 1 : 0);
+ };
+
+ // Argument counts/types.
+ //
+ template <typename... A>
+ struct function_args
+ {
+ static const size_t max = sizeof...(A);
+ static const size_t min = max - function_args_opt<A...>::count;
+
+ // VC15 doesn't realize that a pointer to static object (in our case it is
+ // &value_trair<T>::value_type) is constexpr.
+ //
+#if !defined(_MSC_VER) || _MSC_VER > 1910
+ static constexpr const optional<const value_type*> types[max] = {
+ function_arg<A>::type ()...};
+#else
+ static const optional<const value_type*> types[max];
+#endif
+ };
+
+ template <typename... A>
+#if !defined(_MSC_VER) || _MSC_VER > 1910
+ constexpr const optional<const value_type*>
+ function_args<A...>::types[function_args<A...>::max];
+#else
+ const optional<const value_type*>
+ function_args<A...>::types[function_args<A...>::max] = {
+ function_arg<A>::type ()...};
+#endif
+
+ // Specialization for no arguments.
+ //
+ template <>
+ struct function_args<>
+ {
+ static const size_t max = 0;
+ static const size_t min = 0;
+
+#if !defined(_MSC_VER) || _MSC_VER > 1910
+ static constexpr const optional<const value_type*>* types = nullptr;
+#else
+ static const optional<const value_type*>* const types;
+#endif
+ };
+
+ // Cast data/thunk.
+ //
+ template <typename R, typename... A>
+ struct function_cast
+ {
+ // A pointer to a standard layout struct is a pointer to its first data
+ // member, which in our case is the cast thunk.
+ //
+ struct data
+ {
+ value (*const thunk) (vector_view<value>, const void*);
+ R (*const impl) (A...);
+ };
+
+ static value
+ thunk (vector_view<value> args, const void* d)
+ {
+ return thunk (move (args),
+ static_cast<const data*> (d)->impl,
+ std::index_sequence_for<A...> ());
+ }
+
+ template <size_t... i>
+ static value
+ thunk (vector_view<value> args,
+ R (*impl) (A...),
+ std::index_sequence<i...>)
+ {
+ return value (
+ impl (
+ function_arg<A>::cast (
+ i < args.size () ? &args[i] : nullptr)...));
+ }
+ };
+
+ // Specialization for void return type. In this case we return NULL value.
+ //
+ template <typename... A>
+ struct function_cast<void, A...>
+ {
+ struct data
+ {
+ value (*const thunk) (vector_view<value>, const void*);
+ void (*const impl) (A...);
+ };
+
+ static value
+ thunk (vector_view<value> args, const void* d)
+ {
+ thunk (move (args),
+ static_cast<const data*> (d)->impl,
+ std::index_sequence_for<A...> ());
+ return value (nullptr);
+ }
+
+ template <size_t... i>
+ static void
+ thunk (vector_view<value> args,
+ void (*impl) (A...),
+ std::index_sequence<i...>)
+ {
+ impl (function_arg<A>::cast (i < args.size () ? &args[i] : nullptr)...);
+ }
+ };
+
+ // Customization for coerced lambdas (see below).
+ //
+#if defined(__GNUC__) && !defined(__clang__) && __GNUC__ < 6
+ template <typename L, typename R, typename... A>
+ struct function_cast_lamb
+ {
+ struct data
+ {
+ value (*const thunk) (vector_view<value>, const void*);
+ R (L::*const impl) (A...) const;
+ };
+
+ static value
+ thunk (vector_view<value> args, const void* d)
+ {
+ return thunk (move (args),
+ static_cast<const data*> (d)->impl,
+ std::index_sequence_for<A...> ());
+ }
+
+ template <size_t... i>
+ static value
+ thunk (vector_view<value> args,
+ R (L::*impl) (A...) const,
+ std::index_sequence<i...>)
+ {
+ const L* l (nullptr); // Undefined behavior.
+
+ return value (
+ (l->*impl) (
+ function_arg<A>::cast (
+ i < args.size () ? &args[i] : nullptr)...));
+ }
+ };
+
+ template <typename L, typename... A>
+ struct function_cast_lamb<L, void, A...>
+ {
+ struct data
+ {
+ value (*const thunk) (vector_view<value>, const void*);
+ void (L::*const impl) (A...) const;
+ };
+
+ static value
+ thunk (vector_view<value> args, const void* d)
+ {
+ thunk (move (args),
+ static_cast<const data*> (d)->impl,
+ std::index_sequence_for<A...> ());
+ return value (nullptr);
+ }
+
+ template <size_t... i>
+ static void
+ thunk (vector_view<value> args,
+ void (L::*impl) (A...) const,
+ std::index_sequence<i...>)
+ {
+ const L* l (nullptr);
+ (l->*impl) (
+ function_arg<A>::cast (
+ i < args.size () ? &args[i] : nullptr)...);
+ }
+ };
+#endif
+
+ // Customization for member functions.
+ //
+ template <typename R, typename T>
+ struct function_cast_memf
+ {
+ struct data
+ {
+ value (*const thunk) (vector_view<value>, const void*);
+ R (T::*const impl) () const;
+ };
+
+ static value
+ thunk (vector_view<value> args, const void* d)
+ {
+ auto mf (static_cast<const data*> (d)->impl);
+ return value ((function_arg<T>::cast (&args[0]).*mf) ());
+ }
+ };
+
+ template <typename T>
+ struct function_cast_memf<void, T>
+ {
+ struct data
+ {
+ value (*const thunk) (vector_view<value>, const void*);
+ void (T::*const impl) () const;
+ };
+
+ static value
+ thunk (vector_view<value> args, const void* d)
+ {
+ auto mf (static_cast<const data*> (d)->impl);
+ (function_arg<T>::cast (args[0]).*mf) ();
+ return value (nullptr);
+ }
+ };
+
+ // Customization for data members.
+ //
+ template <typename R, typename T>
+ struct function_cast_memd
+ {
+ struct data
+ {
+ value (*const thunk) (vector_view<value>, const void*);
+ R T::*const impl;
+ };
+
+ static value
+ thunk (vector_view<value> args, const void* d)
+ {
+ auto dm (static_cast<const data*> (d)->impl);
+ return value (move (function_arg<T>::cast (&args[0]).*dm));
+ }
+ };
+
+ struct function_family::entry
+ {
+ string name;
+ const string& qual;
+ function_impl* thunk;
+
+ template <typename R, typename... A>
+ void
+ operator= (R (*impl) (A...)) &&
+ {
+ using args = function_args<A...>;
+ using cast = function_cast<R, A...>;
+
+ insert (move (name),
+ function_overload (
+ nullptr,
+ args::min,
+ args::max,
+ function_overload::types (args::types, args::max),
+ thunk,
+ typename cast::data {&cast::thunk, impl}));
+ }
+
+ // Support for assigning a (capture-less) lambda.
+ //
+ // GCC up until version 6 has a bug (#62052) that is triggered by calling
+ // a lambda that takes a by-value argument via its "decayed" function
+ // pointer. To work around this we are not going to decay it and instead
+ // will call its operator() on NULL pointer; yes, undefined behavior, but
+ // better than a guaranteed crash.
+ //
+#if defined(__GNUC__) && !defined(__clang__) && __GNUC__ < 6
+ template <typename L>
+ void
+ operator= (const L&) &&
+ {
+ move (*this).coerce_lambda (&L::operator());
+ }
+
+ template <typename L, typename R, typename... A>
+ void
+ coerce_lambda (R (L::*op) (A...) const) &&
+ {
+ using args = function_args<A...>;
+ using cast = function_cast_lamb<L, R, A...>;
+
+ insert (move (name),
+ function_overload (
+ nullptr,
+ args::min,
+ args::max,
+ function_overload::types (args::types, args::max),
+ thunk,
+ typename cast::data {&cast::thunk, op}));
+ }
+#else
+ template <typename L>
+ void
+ operator= (const L& l) &&
+ {
+ move (*this).operator= (decay_lambda (&L::operator(), l));
+ }
+
+ template <typename L, typename R, typename... A>
+ static auto
+ decay_lambda (R (L::*) (A...) const, const L& l) -> R (*) (A...)
+ {
+ return static_cast<R (*) (A...)> (l);
+ }
+#endif
+
+ // Support for assigning a pointer to member function (e.g. an accessor).
+ //
+ // For now we don't support passing additional (to this) arguments though
+ // we could probably do that. The issues would be the argument passing
+ // semantics (e.g., what if it's const&) and the optional/default argument
+ // handling.
+ //
+ template <typename R, typename T>
+ void
+ operator= (R (T::*mf) () const) &&
+ {
+ using args = function_args<T>;
+ using cast = function_cast_memf<R, T>;
+
+ insert (move (name),
+ function_overload (
+ nullptr,
+ args::min,
+ args::max,
+ function_overload::types (args::types, args::max),
+ thunk,
+ typename cast::data {&cast::thunk, mf}));
+ }
+
+ // Support for assigning a pointer to data member.
+ //
+ template <typename R, typename T>
+ void
+ operator= (R T::*dm) &&
+ {
+ using args = function_args<T>;
+ using cast = function_cast_memd<R, T>;
+
+ insert (move (name),
+ function_overload (
+ nullptr,
+ args::min,
+ args::max,
+ function_overload::types (args::types, args::max),
+ thunk,
+ typename cast::data {&cast::thunk, dm}));
+ }
+
+ private:
+ void
+ insert (string, function_overload) const;
+ };
+
+ inline auto function_family::
+ operator[] (string name) const -> entry
+ {
+ return entry {move (name), qual_, thunk_};
+ }
+}
+
+#endif // BUILD2_FUNCTION_HXX
generated by cgit v1.1 at 2024-11-13 23:57:49 +0000