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This removes the indirect functors from <bits/predefined_ops.h> that are used by our STL algorithms. Currently we wrap all predicates and values into callables which accept iterator arguments, and automatically dereference the iterators. With this change we no longer do that dereferencing and so all predicates are passed values not iterators, and the algorithms that invoke those predicates must dereference the iterators. This avoids wrapping user-provided predicates into another predicate that does the dereferencing. User-provided predicates are now passed unchanged to our internal algos like __search_n. For the overloads that take a value instead of a predicate, we still need to create a predicate that does comparison to the value, but we can now use std::less<void> and std::equal_to<void> as the base predicate and bind the value to those base predicates. Because the "transparent operators" std::less<void> and std::equal_to<void> were not added until C++14, this change defines those explicit specializations unconditionally for C++98 and C++11 too (but the default template arguments that make std::less<> and std::equal_to<> refer to those specializations are still only present for C++14 and later, because we don't need to rely on those default template arguments for our internal uses). When binding a predicate and a value into a new call wrapper, we now decide whether to store the predicate by value when it's an empty type or a scalar (such as a function pointer). This avoids a double-indirection through function pointers, and avoids storing and invoking stateless empty functors through a reference. For C++11 and later we also use [[no_unique_address]] to avoid wasted storage for empty predicates (which includes all standard relational ops, such as std::less). The call wrappers in bits/predefined_ops.h all have non-const operator() because we can't be sure that the predicates they wrap are const-invocable. The requirements in [algorithms.requirements] for Predicate and BinaryPredicate template arguments require pred(*i) to be valid, but do not require that std::to_const(pred)(*i) has to be valid, and similarly for binary_pred. libstdc++-v3/ChangeLog: * include/bits/predefined_ops.h (equal_to, less): Define aliases for std::equal_to<void> and std::less<void>. (bind1st, bind2nd, not1, __equal_to): New object generator functions for adapting predicates. (__iter_less_iter, __iter_less_val, __iter_comp_val) (__val_less_iter, __val_comp_iter, __iter_equal_to_iter) (__iter_equal_to_val, __iter_comp_iter, __negate): Remove all object generator functions and the class templates they return. * include/bits/stl_algo.h (__move_median_to_first, __find_if_not) (__find_if_not_n, __search_n_aux, find_end, find_if_not) (__remove_copy_if, remove_copy, remove_copy_if, remove) (remove_if, __adjacent_find, __unique, unique, __unique_copy) (__unique_copy_1, __stable_partition_adaptive, stable_partition) (__heap_select, __partial_sort_copy, partial_sort_copy) (__unguarded_linear_insert, __insertion_sort) (__unguarded_insertion_sort, __unguarded_partition) (lower_bound, __upper_bound, upper_bound, __equal_range) (equal_range, binary_search, __move_merge_adaptive) (__move_merge_adaptive_backward, __merge_adaptive_resize) (__merge_without_buffer, inplace_merge, __move_merge) (__includes, includes, __next_permutation, next_permutation) (__prev_permutation, prev_permutation, __replace_copy_if) (replace_copy, replace_copy_if, __is_sorted_until) (is_sorted_until, __minmax_element, minmax_element, minmax) (is_permutation, __is_permutation, find, find_if, adjacent_find) (count, count_if, search, search_n, unique_copy, partial_sort) (nth_element, sort, __merge, merge, stable_sort, __set_union) (set_union, __set_intersection, set_intersection) (__set_difference, set_difference, __set_symmetric_difference) (set_symmetric_difference, __min_element, min_element) (__max_element, max_element, min, max): Use direct predicates instead of __iter_equal_to_iter, __iter_comp_iter, and __iter_less_iter, __negate etc. Dereference iterators when invoking predicates. * include/bits/stl_algobase.h (__lexicographical_compare_impl) (__lexicographical_compare::__lc, __lower_bound, lower_bound) (lexicographical_compare, __mismatch, mismatch, __find_if) (__count_if, __remove_if, __search, __is_permutation) (is_permutation, search): Likewise. * include/bits/stl_function.h (equal_to<void>, less<void>): Define transparent comparison functions for C++98 and C++11. * include/bits/stl_heap.h (__is_heap_until, __is_heap) (__push_heap, push_heap, __adjust_heap, pop_heap, make_heap) (sort_heap, is_heap_until, is_heap): Likewise. * include/std/deque (erase_if): Remove call to __pred_iter. (erase): Replace __iter_equals_val with __equal_to. * include/std/inplace_vector (erase_if, erase): Likewise. * include/std/string (erase_if, erase): Likewise. * include/std/vector (erase_if, erase): Likewise. Reviewed-by: Tomasz Kamiński <tkaminsk@redhat.com> Reviewed-by: François Dumont <frs.dumont@gmail.com>
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