Merge branch 'main' into DRTVWR-591-maint-X

# Conflicts:
#	doc/contributions.txt
#	indra/newview/llpanelprofile.cpp
#	indra/newview/llspatialpartition.cpp

1 files changed, 130 insertions, 14 deletions

diff --git a/indra/llcommon/apply.h b/indra/llcommon/apply.h
index 7c58d63bc0..cf6161ed50 100644
--- a/indra/llcommon/apply.h
+++ b/indra/llcommon/apply.h
@@ -12,8 +12,11 @@
 #if ! defined(LL_APPLY_H)
 #define LL_APPLY_H
 
+#include "llexception.h"
 #include <boost/type_traits/function_traits.hpp>
+#include <functional>               // std::mem_fn()
 #include <tuple>
+#include <type_traits>              // std::is_member_pointer
 
 namespace LL
 {
@@ -54,20 +57,67 @@ namespace LL
         },                                                          \
         (ARGS))
 
-#if __cplusplus >= 201703L
+/*****************************************************************************
+*   invoke()
+*****************************************************************************/
+#if __cpp_lib_invoke >= 201411L
 
 // C++17 implementation
-using std::apply;
+using std::invoke;
+
+#else  // no std::invoke
+
+// Use invoke() to handle pointer-to-method:
+// derived from https://stackoverflow.com/a/38288251
+template<typename Fn, typename... Args, 
+         typename std::enable_if<std::is_member_pointer<typename std::decay<Fn>::type>::value,
+                                 int>::type = 0 >
+auto invoke(Fn&& f, Args&&... args)
+{
+    return std::mem_fn(std::forward<Fn>(f))(std::forward<Args>(args)...);
+}
+
+template<typename Fn, typename... Args, 
+         typename std::enable_if<!std::is_member_pointer<typename std::decay<Fn>::type>::value,
+                                 int>::type = 0 >
+auto invoke(Fn&& f, Args&&... args)
+{
+    return std::forward<Fn>(f)(std::forward<Args>(args)...);
+}
+
+#endif // no std::invoke
+
+/*****************************************************************************
+*   apply(function, tuple); apply(function, array)
+*****************************************************************************/
+#if __cpp_lib_apply >= 201603L
+
+// C++17 implementation
+// We don't just say 'using std::apply;' because that template is too general:
+// it also picks up the apply(function, vector) case, which we want to handle
+// below.
+template <typename CALLABLE, typename... ARGS>
+auto apply(CALLABLE&& func, const std::tuple<ARGS...>& args)
+{
+    return std::apply(std::forward<CALLABLE>(func), args);
+}
 
 #else // C++14
 
 // Derived from https://stackoverflow.com/a/20441189
 // and https://en.cppreference.com/w/cpp/utility/apply
-template <typename CALLABLE, typename TUPLE, std::size_t... I>
-auto apply_impl(CALLABLE&& func, TUPLE&& args, std::index_sequence<I...>)
+template <typename CALLABLE, typename... ARGS, std::size_t... I>
+auto apply_impl(CALLABLE&& func, const std::tuple<ARGS...>& args, std::index_sequence<I...>)
 {
+    // We accept const std::tuple& so a caller can construct an tuple on the
+    // fly. But std::get<I>(const tuple) adds a const qualifier to everything
+    // it extracts. Get a non-const ref to this tuple so we can extract
+    // without the extraneous const.
+    auto& non_const_args{ const_cast<std::tuple<ARGS...>&>(args) };
+
     // call func(unpacked args)
-    return std::forward<CALLABLE>(func)(std::move(std::get<I>(args))...);
+    return invoke(std::forward<CALLABLE>(func),
+                  std::forward<ARGS>(std::get<I>(non_const_args))...);
 }
 
 template <typename CALLABLE, typename... ARGS>
@@ -81,6 +131,8 @@ auto apply(CALLABLE&& func, const std::tuple<ARGS...>& args)
                       std::index_sequence_for<ARGS...>{});
 }
 
+#endif // C++14
+
 // per https://stackoverflow.com/a/57510428/5533635
 template <typename CALLABLE, typename T, size_t SIZE>
 auto apply(CALLABLE&& func, const std::array<T, SIZE>& args)
@@ -88,28 +140,92 @@ auto apply(CALLABLE&& func, const std::array<T, SIZE>& args)
     return apply(std::forward<CALLABLE>(func), std::tuple_cat(args));
 }
 
+/*****************************************************************************
+*   bind_front()
+*****************************************************************************/
+// To invoke a non-static member function with a tuple, you need a callable
+// that binds your member function with an instance pointer or reference.
+// std::bind_front() is perfect: std::bind_front(&cls::method, instance).
+// Unfortunately bind_front() only enters the standard library in C++20.
+#if __cpp_lib_bind_front >= 201907L
+
+// C++20 implementation
+using std::bind_front;
+
+#else  // no std::bind_front()
+
+template<typename Fn, typename... Args, 
+         typename std::enable_if<!std::is_member_pointer<typename std::decay<Fn>::type>::value,
+                                 int>::type = 0 >
+auto bind_front(Fn&& f, Args&&... args)
+{
+    // Don't use perfect forwarding for f or args: we must bind them for later.
+    return [f, pfx_args=std::make_tuple(args...)]
+        (auto&&... sfx_args)
+    {
+        // Use perfect forwarding for sfx_args because we use them as soon as
+        // we receive them.
+        return apply(
+            f,
+            std::tuple_cat(pfx_args,
+                           std::make_tuple(std::forward<decltype(sfx_args)>(sfx_args)...)));
+    };
+}
+
+template<typename Fn, typename... Args, 
+         typename std::enable_if<std::is_member_pointer<typename std::decay<Fn>::type>::value,
+                                 int>::type = 0 >
+auto bind_front(Fn&& f, Args&&... args)
+{
+    return bind_front(std::mem_fn(std::forward<Fn>(f)), std::forward<Args>(args)...);
+}
+
+#endif // C++20 with std::bind_front()
+
+/*****************************************************************************
+*   apply(function, std::vector)
+*****************************************************************************/
 // per https://stackoverflow.com/a/28411055/5533635
 template <typename CALLABLE, typename T, std::size_t... I>
 auto apply_impl(CALLABLE&& func, const std::vector<T>& args, std::index_sequence<I...>)
 {
+    return apply(std::forward<CALLABLE>(func),
+                 std::make_tuple(args[I]...));
+}
+
+// produce suitable error if apply(func, vector) is the wrong size for func()
+void apply_validate_size(size_t size, size_t arity);
+
+/// possible exception from apply() validation
+struct apply_error: public LLException
+{
+    apply_error(const std::string& what): LLException(what) {}
+};
+
+template <size_t ARITY, typename CALLABLE, typename T>
+auto apply_n(CALLABLE&& func, const std::vector<T>& args)
+{
+    apply_validate_size(args.size(), ARITY);
     return apply_impl(std::forward<CALLABLE>(func),
-                      std::make_tuple(std::forward<T>(args[I])...),
-                      I...);
+                      args,
+                      std::make_index_sequence<ARITY>());
 }
 
-// this goes beyond C++17 std::apply()
+/**
+ * apply(function, std::vector) goes beyond C++17 std::apply(). For this case
+ * @a function @emph cannot be variadic: the compiler must know at compile
+ * time how many arguments to pass. This isn't Python. (But see apply_n() to
+ * pass a specific number of args to a variadic function.)
+ */
 template <typename CALLABLE, typename T>
 auto apply(CALLABLE&& func, const std::vector<T>& args)
 {
+    // infer arity from the definition of func
     constexpr auto arity = boost::function_traits<CALLABLE>::arity;
-    assert(args.size() == arity);
-    return apply_impl(std::forward<CALLABLE>(func),
-                      args,
-                      std::make_index_sequence<arity>());
+    // now that we have a compile-time arity, apply_n() works
+    return apply_n<arity>(std::forward<CALLABLE>(func), args);
 }
 
-#endif // C++14
-
 } // namespace LL
 
 #endif /* ! defined(LL_APPLY_H) */