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template metaprogramming instead of macros
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C++ (and myself) hates macros.  If we could do the same thing in both
preprocessor and template, we shall choose template.  This particular
part of the ruby header is one of such situations.
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@shyouhei
shyouhei committed Jan 28, 2020
1 parent ab33b3d commit 01825e8
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186 changes: 185 additions & 1 deletion include/ruby/backward/cxxanyargs.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -11,6 +11,8 @@
/// meant to be a backwards compatibility shim. Please stick to
/// C++ 98 and never use newer features, like `constexpr`.

extern "C++" {

/// @brief The main namespace.
/// @note The name "ruby" might already be taken, but that must not be a
/// problem because namespaces are allowed to reopen.
Expand Down Expand Up @@ -433,7 +435,189 @@ rb_ivar_foreach(VALUE q, int_type *w, VALUE e)
}

/// @}
}}}

/// @brief Driver for *_define_method
///
/// ::rb_define_method function for instance takes a pointer to ANYARGS-ed
/// functions, which in fact varies 18 different prototypes. We still need to
/// preserve ANYARGS for storages but why not check the consistencies if
/// possible. In C++ a function has its own prototype, which is a compile-time
/// constant (static type) by nature. We can list up all the possible input
/// types and provide warnings for other cases. This is such attempt.
namespace define_method {

/// @brief Template metaprogramming to generate function prototypes.
/// @tparam T Type of method id (`ID` or `const char*` in practice).
/// @tparam F Definition driver e.g. ::rb_define_method.
template<typename T, void (*F)(VALUE klass, T mid, type *func, int arity)>
struct driver {

/// @brief Defines a method
/// @tparam N Arity of the function.
/// @tparam U The function in question
template<int N, typename U>
struct engine {

/* :TODO: Following deprecation attribute renders tons of warnings (one
* per every method definitions), which is annoying. Of course
* annoyance is the core feature of deprecation warnings... But that
* could be too much, especially when the warnings happen inside of
* machine-generated programs. And SWIG is known to do such thing.
* The new (granular) API was introduced in API version 2.7. As of
* this writing the version is 2.8. Let's warn this later, some time
* during 3.x. Hopefully codes in old (ANYARGS-ed) format should be
* less than now. */
#if (RUBY_API_VERSION_MAJOR * 100 + RUBY_API_VERSION_MINOR) >= 301
RUBY_CXX_DEPRECATED("use of ANYARGS is deprecated")
#endif
/// @brief Defines klass#mid as func, whose arity is N.
/// @param[in] klass Where the method lives.
/// @param[in] mid Name of the method to define.
/// @param[in] func Function that implements klass#mid.
/// @deprecated Pass corrctly typed function instead.
static inline void
define(VALUE klass, T mid, type func)
{
F(klass, mid, func, N);
}

/// @brief Defines klass#mid as func, whose arity is N.
/// @param[in] klass Where the method lives.
/// @param[in] mid Name of the method to define.
/// @param[in] func Function that implements klass#mid.
static inline void
define(VALUE klass, T mid, U func)
{
F(klass, mid, reinterpret_cast<type *>(func), N);
}
};

/// @cond INTERNAL_MACRO
template<int N, bool = false> struct specific : public engine<N, type *> {};
template<bool b> struct specific<15, b> : public engine<15, VALUE(*)(VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE)> {};
template<bool b> struct specific<14, b> : public engine<14, VALUE(*)(VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE)> {};
template<bool b> struct specific<13, b> : public engine<13, VALUE(*)(VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE)> {};
template<bool b> struct specific<12, b> : public engine<12, VALUE(*)(VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE)> {};
template<bool b> struct specific<11, b> : public engine<11, VALUE(*)(VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE)> {};
template<bool b> struct specific<10, b> : public engine<10, VALUE(*)(VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE)> {};
template<bool b> struct specific< 9, b> : public engine< 9, VALUE(*)(VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE)> {};
template<bool b> struct specific< 8, b> : public engine< 8, VALUE(*)(VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE)> {};
template<bool b> struct specific< 7, b> : public engine< 7, VALUE(*)(VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE)> {};
template<bool b> struct specific< 6, b> : public engine< 6, VALUE(*)(VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE)> {};
template<bool b> struct specific< 5, b> : public engine< 5, VALUE(*)(VALUE, VALUE, VALUE, VALUE, VALUE, VALUE)> {};
template<bool b> struct specific< 4, b> : public engine< 4, VALUE(*)(VALUE, VALUE, VALUE, VALUE, VALUE)> {};
template<bool b> struct specific< 3, b> : public engine< 3, VALUE(*)(VALUE, VALUE, VALUE, VALUE)> {};
template<bool b> struct specific< 2, b> : public engine< 2, VALUE(*)(VALUE, VALUE, VALUE)> {};
template<bool b> struct specific< 1, b> : public engine< 1, VALUE(*)(VALUE, VALUE)> {};
template<bool b> struct specific< 0, b> : public engine< 0, VALUE(*)(VALUE)> {};
template<bool b> struct specific<-1, b> : public engine<-1, VALUE(*)(int argc, VALUE argv, VALUE self)> {

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@nobu

nobu Jan 28, 2020

Member

Isn’t VALUE *argv?

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@shyouhei

shyouhei Jan 28, 2020

Author Member

Ah, yes. Must fix.

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@shyouhei

shyouhei Jan 28, 2020

Author Member

03df02e
using engine<-1, VALUE(*)(int argc, VALUE argv, VALUE self)>::define;
static inline void define(VALUE c, T m, VALUE(*f)(int argc, VALUE *argv, VALUE self)) { F(c, m, reinterpret_cast<type *>(f), -1); }
static inline void define(VALUE c, T m, VALUE(*f)(int argc, const VALUE *argv, VALUE self)) { F(c, m, reinterpret_cast<type *>(f), -1); }
static inline void define(VALUE c, T m, VALUE(*f)(int argc, const VALUE *argv, VALUE self, VALUE)) { F(c, m, reinterpret_cast<type *>(f), -1); }
};
template<bool b> struct specific<-2, b> : public engine<-2, VALUE(*)(VALUE, VALUE)> {};
/// @endcond
};

/* We could perhaps merge this struct into the one above using variadic
* template parameters if we could assume C++11, but sadly we cannot. */
template<typename T, void (*F)(T mid, type func, int arity)>
struct driver0 {
template<int N, typename U>
struct engine {
RUBY_CXX_DEPRECATED("use of ANYARGS is deprecated")
static inline void
define(T mid, type func)
{
F(mid, func, N);
}
static inline void
define(T mid, U func)
{
F(mid, reinterpret_cast<type *>(func), N);
}
};
/// @cond INTERNAL_MACRO
template<int N, bool = false> struct specific : public engine<N, type *> {};
template<bool b> struct specific<15, b> : public engine<15, VALUE(*)(VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE)> {};
template<bool b> struct specific<14, b> : public engine<14, VALUE(*)(VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE)> {};
template<bool b> struct specific<13, b> : public engine<13, VALUE(*)(VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE)> {};
template<bool b> struct specific<12, b> : public engine<12, VALUE(*)(VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE)> {};
template<bool b> struct specific<11, b> : public engine<11, VALUE(*)(VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE)> {};
template<bool b> struct specific<10, b> : public engine<10, VALUE(*)(VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE)> {};
template<bool b> struct specific< 9, b> : public engine< 9, VALUE(*)(VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE)> {};
template<bool b> struct specific< 8, b> : public engine< 8, VALUE(*)(VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE)> {};
template<bool b> struct specific< 7, b> : public engine< 7, VALUE(*)(VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE)> {};
template<bool b> struct specific< 6, b> : public engine< 6, VALUE(*)(VALUE, VALUE, VALUE, VALUE, VALUE, VALUE, VALUE)> {};
template<bool b> struct specific< 5, b> : public engine< 5, VALUE(*)(VALUE, VALUE, VALUE, VALUE, VALUE, VALUE)> {};
template<bool b> struct specific< 4, b> : public engine< 4, VALUE(*)(VALUE, VALUE, VALUE, VALUE, VALUE)> {};
template<bool b> struct specific< 3, b> : public engine< 3, VALUE(*)(VALUE, VALUE, VALUE, VALUE)> {};
template<bool b> struct specific< 2, b> : public engine< 2, VALUE(*)(VALUE, VALUE, VALUE)> {};
template<bool b> struct specific< 1, b> : public engine< 1, VALUE(*)(VALUE, VALUE)> {};
template<bool b> struct specific< 0, b> : public engine< 0, VALUE(*)(VALUE)> {};
template<bool b> struct specific<-1, b> : public engine<-1, VALUE(*)(int argc, VALUE argv, VALUE self)> {
using engine<-1, VALUE(*)(int argc, VALUE argv, VALUE self)>::define;
static inline void define(T m, VALUE(*f)(int argc, VALUE *argv, VALUE self)) { F(m, reinterpret_cast<type *>(f), -1); }
static inline void define(T m, VALUE(*f)(int argc, const VALUE *argv, VALUE self)) { F(m, reinterpret_cast<type *>(f), -1); }
static inline void define(T m, VALUE(*f)(int argc, const VALUE *argv, VALUE self, VALUE)) { F(m, reinterpret_cast<type *>(f), -1); }
};
template<bool b> struct specific<-2, b> : public engine<-2, VALUE(*)(VALUE, VALUE)> {};
/// @endcond
};

/// @brief Dispatches appropriate driver for ::rb_define_method
struct rb_define_method : public driver <const char *, ::rb_define_method> {};

/// @brief Dispatches appropriate driver for ::rb_define_method_id
struct rb_define_method_id : public driver <ID, ::rb_define_method_id> {};

/// @brief Dispatches appropriate driver for ::rb_define_private_method
struct rb_define_private_method : public driver <const char *, ::rb_define_private_method> {};

/// @brief Dispatches appropriate driver for ::rb_define_protected_method
struct rb_define_protected_method : public driver <const char *, ::rb_define_protected_method> {};

/// @brief Dispatches appropriate driver for ::rb_define_singleton_method
struct rb_define_singleton_method : public driver <const char *, ::rb_define_singleton_method> {};

/// @brief Dispatches appropriate driver for ::rb_define_module_function
struct rb_define_module_function : public driver <const char *, ::rb_define_module_function> {};

/// @brief Dispatches appropriate driver for ::rb_define_global_function
struct rb_define_global_function : public driver0<const char *, ::rb_define_global_function> {};

/// @brief Defines klass\#mid.
/// @param klass Where the method lives.
/// @copydetails #rb_define_global_function
#define rb_define_method(klass, mid, func, arity) ruby::backward::cxxanyargs::define_method::rb_define_method::specific<arity>::define(klass, mid, func)

/// @copydoc #rb_define_method
#define rb_define_method_id(klass, mid, func, arity) ruby::backward::cxxanyargs::define_method::rb_define_method_id::specific<arity>::define(klass, mid, func)

/// @brief Defines klass\#mid and makes it private.
/// @copydetails #rb_define_method
#define rb_define_private_method(klass, mid, func, arity) ruby::backward::cxxanyargs::define_method::rb_define_private_method::specific<arity>::define(klass, mid, func)

/// @brief Defines klass\#mid and makes it protected.
/// @copydetails #rb_define_method
#define rb_define_protected_method(klass, mid, func, arity) ruby::backward::cxxanyargs::define_method::rb_define_protected_method::specific<arity>::define(klass, mid, func)

/// @brief Defines klass.mid.
/// @copydetails #rb_define_method
#define rb_define_singleton_method(klass, mid, func, arity) ruby::backward::cxxanyargs::define_method::rb_define_singleton_method::specific<arity>::define(klass, mid, func)

/// @brief Defines klass\#mid and makes it a module function.
/// @copydetails #rb_define_method
#define rb_define_module_function(klass, mid, func, arity) ruby::backward::cxxanyargs::define_method::rb_define_module_function::specific<arity>::define(klass, mid, func)

/// @brief Defines ::rb_cKerbel \#mid.
/// @param mid Name of the defining method.
/// @param func Implementation of \#mid.
/// @param arity Arity of \#mid.
#define rb_define_global_function(mid, func, arity) ruby::backward::cxxanyargs::define_method::rb_define_global_function::specific<arity>::define(mid, func)

}}}}}

using namespace ruby::backward::cxxanyargs;
#endif // RUBY_BACKWARD_CXXANYARGS_HPP
12 changes: 4 additions & 8 deletions include/ruby/ruby.h
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Original file line number Diff line number Diff line change
Expand Up @@ -2654,12 +2654,8 @@ void ruby_sig_finalize(void);
RUBY_SYMBOL_EXPORT_END

#if defined(__cplusplus)
#if 0
{ /* satisfy cc-mode */
#endif
} /* extern "C" { */
extern "C++" {
#endif
#include "backward/cxxanyargs.hpp"
#else

#if defined(HAVE_BUILTIN___BUILTIN_TYPES_COMPATIBLE_P)
# define rb_f_notimplement_p(f) __builtin_types_compatible_p(__typeof__(f),__typeof__(rb_f_notimplement))
Expand Down Expand Up @@ -2937,15 +2933,15 @@ RB_METHOD_DEFINITION_DECL(rb_define_global_function, (1,2), (const char *name),

#endif

#endif /* __cplusplus */

#if defined(RUBY_DEVEL) && RUBY_DEVEL && (!defined(__cplusplus) || defined(RB_METHOD_DEFINITION_DECL))
# define RUBY_METHOD_FUNC(func) (func)
#else
# define RUBY_METHOD_FUNC(func) ((VALUE (*)(ANYARGS))(func))
#endif

#ifdef __cplusplus
#include "backward/cxxanyargs.hpp"

#if 0
{ /* satisfy cc-mode */
#endif
Expand Down

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