std::meta::size_of

 

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Checking string literals is_string_literal Helper types info tuple_size tuple_element is_applicable_type is_nothrow_applicable_type      apply_result variant_size variant_alternative type_order exception Promoting to static storage reflect_constant_string reflect_constant_array define_static_string define_static_array define_static_object Operator representations operators operator_of symbol_of u8symbol_of Names and locations has_identifier identifier_of u8identifier_of display_string_of u8display_string_of source_location_of Reflection queries -> Access control context access_context

Member accessibility queries is_accessible has_inaccessible_nonstatic_   data_members has_inaccessible_bases has_inaccessible_subobjects      Scope identification current_function current_class current_namespace Reflection member queries members_of bases_of static_data_members_of nonstatic_data_members_of subobjects_of enumerators_of Annotation reflection annotations_of annotations_of_with_type Value extraction extract Reflection substitution reflection_range can_substitute substitute Expression result reflection reflect_constant reflect_object reflect_function Class definition generation data_member_options data_member_spec is_data_member_spec define_aggregate

Primary type categories is_void_type is_null_pointer_type is_integral_type is_floating_point_type is_array_type is_pointer_type is_lvalue_reference_type is_rvalue_reference_type is_member_object_pointer_type is_member_function_pointer_type      is_enum_type is_union_type is_class_type is_function_type is_reflection_type Composite type categories is_reference_type is_arithmetic_type is_fundamental_type is_object_type is_scalar_type is_compound_type is_member_pointer_type Type properties -> Type relations is_same_type is_base_of_type is_virtual_base_of_type is_convertible_type is_nothrow_convertible_type is_layout_compatible_type is_pointer_interconvertible_   base_of_type is_invocable_type is_invocable_r_type is_nothrow_invocable_type is_nothrow_invocable_r_type

Const-volatile modifications remove_const remove_volatile remove_cv add_const add_volatile add_cv Reference modifications remove_reference add_lvalue_reference add_rvalue_reference Sign modifications make_signed make_unsigned Array modifications remove_extent remove_all_extents Pointer modifications remove_pointer add_pointer Other transformations remove_cvref decay common_type common_reference underlying_type invoke_result unwrap_reference unwrap_ref_decay

 

Reflection types and queries

Reflection queries type_of object_of constant_of is_public is_protected is_private is_virtual is_pure_virtual is_override is_final is_deleted is_defaulted is_user_provided is_user_declared is_explicit is_noexcept is_bit_field is_enumerator is_annotation is_const is_volatile is_mutable_member is_lvalue_reference_qualified is_rvalue_reference_qualified has_static_storage_duration has_thread_storage_duration has_automatic_storage_duration      has_internal_linkage has_module_linkage has_external_linkage has_c_language_linkage has_linkage is_complete_type is_enumerable_type is_variable is_type is_namespace is_type_alias is_namespace_alias is_function is_conversion_function is_operator_function is_literal_operator is_special_member_function is_constructor is_default_constructor is_copy_constructor

is_move_constructor is_assignment is_copy_assignment is_move_assignment is_destructor is_function_parameter is_explicit_object_parameter has_default_argument is_vararg_function is_template is_function_template is_variable_template is_class_template is_alias_template is_conversion_function_template      is_operator_function_template is_literal_operator_template is_constructor_template is_concept is_value is_object is_structured_binding is_class_member is_namespace_member is_nonstatic_data_member is_static_member is_base has_default_member_initializer has_parent parent_of dealias has_template_arguments template_of template_arguments_of parameters_of variable_of return_type_of Reflection layout queries member_offset offset_of size_of alignment_of bit_size_of Type properties is_const_type is_volatile_type is_trivially_copyable_type

is_standard_layout_type is_empty_type is_polymorphic_type is_abstract_type is_final_type is_aggregate_type is_structural_type is_signed_type is_unsigned_type is_bounded_array_type is_unbounded_array_type is_scoped_enum_type is_constructible_type is_default_constructible_type is_copy_constructible_type is_move_constructible_type is_assignable_type is_copy_assignable_type is_move_assignable_type is_swappable_with_type is_swappable_type is_destructible_type is_trivially_constructible_type is_trivially_default_constructible_type is_trivially_copy_constructible_type is_trivially_move_constructible_type is_trivially_assignable_type is_trivially_copy_assignable_type is_trivially_move_assignable_type is_trivially_destructible_type is_nothrow_constructible_type is_nothrow_default_constructible_type is_nothrow_copy_constructible_type is_nothrow_move_constructible_type is_nothrow_assignable_type is_nothrow_copy_assignable_type is_nothrow_move_assignable_type is_nothrow_swappable_with_type is_nothrow_swappable_type is_nothrow_destructible_type is_implicit_lifetime_type has_virtual_destructor has_unique_object_representations reference_constructs_from_temporary reference_converts_from_temporary Type property queries rank extent

 

Defined in header <meta>
consteval std::size_t size_of( std::meta::info r );		(since C++26)

Returns the size of the type or (sub)object represented by r.

Parameters

r

-

a reflection value

Return value

If r represents a type “reference to T”, returns sizeof(T*).

Otherwise, if r represents a type U, returns sizeof(U).

Otherwise, equivalent to std::meta::size_of(std::meta::type_of(r)).

Exceptions

Throws std::meta::exception unless all of the following conditions are met:

• std::meta::dealias(r) represents one of the following:

• type
• object
• (scalar) value
• variable of non-reference type
• non-static data member that is not a bit-field
• direct base class relationship
• data member description whose bit width is ⊥

• If std::meta::dealias(r) represents a type, std::meta::is_complete_type(r) is true.

Notes

This function treats “reference of T” the same as “pointer to T”. This matches the representation of non-static reference members.

The result is non-zero even if r represents a direct base class relationship of an empty base class.

Example

Run this code

#include <meta>

static_assert(std::meta::size_of(^^int) == sizeof(int));
static_assert(std::meta::size_of(^^int*) == sizeof(int*));

consteval bool test()
{
    struct A; 
    // constexpr auto _ = std::meta::size_of(^^A);
        // error: uncaught exception of type 'std::meta::exception';
        // 'what()': 'reflection with incomplete type in size_of'
    return true;
}
static_assert(test());

struct B { int i, j; };
static_assert(sizeof(B) == std::meta::size_of(^^B));

template<class T>
struct C { T m; };
static_assert(size_of(^^C<char>) == sizeof(char));

struct D { int x : 015; };
static_assert(size_of(^^D) == sizeof(int));

// static_assert(size_of(^^D::x) == sizeof(int));
    // error: uncaught exception of type 'std::meta::exception';
    // 'what()': 'reflection not suitable for size_of'

int main() {}

See also

alignment_of (C++26)	returns the alignment of the reflected object or type (function)
bit_size_of (C++26)	returns the size in bits of the reflected object or type (function)