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      offsetof

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      < cpp‎ | types

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      C++
       
      Bibliothèque d'utilitaires
       
      Soutien aux types fondamentaux
      Les types de base
      Original:
      Basic types
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      Types fondamentaux
      Fixe les types entiers largeur (C++11)
      nullptr_t (C++11)
      offsetof
      NULL
      Limites numériques
      Original:
      Numeric limits
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      numeric_limits
      C numérique limite interface
      Informations sur le type d'exécution
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      Runtime type information
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      Caractères de type
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      Type traits
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      Catégories de type primaire
      Original:
      Primary type categories
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      is_void (C++11)
      is_array (C++11)
      is_pointer (C++11)
      is_enum (C++11)
      is_union (C++11)
      is_class (C++11)
      is_function (C++11)
      is_object (C++11)
      is_scalar (C++11)
      is_compound (C++11)
      is_integral (C++11)
      is_floating_point (C++11)
      is_fundamental (C++11)
      is_arithmetic (C++11)
      is_reference (C++11)
      is_lvalue_reference (C++11)
      is_rvalue_reference (C++11)
      is_member_pointer (C++11)
      is_member_object_pointer (C++11)
      is_member_function_pointer (C++11)
      Les propriétés du type
      Original:
      Type properties
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      is_const (C++11)
      is_volatile (C++11)
      is_pod (C++11)
      is_empty (C++11)
      is_polymorphic (C++11)
      is_abstract (C++11)
      Opérations prises en charge
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      Supported operations
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      is_constructible
      is_trivially_constructible
      is_nothrow_constructible      		 (C++11)
      (C++11)
      (C++11)
      is_default_constructible
      is_trivially_default_constructible
      is_nothrow_default_constructible      		 (C++11)
      (C++11)
      (C++11)
      is_copy_constructible
      is_trivially_copy_constructible
      is_nothrow_copy_constructible      		 (C++11)
      (C++11)
      (C++11)
      is_move_constructible
      is_trivially_move_constructible
      is_nothrow_move_constructible      		 (C++11)
      (C++11)
      (C++11)
      is_assignable
      is_trivially_assignable
      is_nothrow_assignable      		 (C++11)
      (C++11)
      (C++11)
      is_copy_assignable
      is_trivially_copy_assignable
      is_nothrow_copy_assignable      		 (C++11)
      (C++11)
      (C++11)
      is_move_assignable
      is_trivially_move_assignable
      is_nothrow_move_assignable      		 (C++11)
      (C++11)
      (C++11)
      is_destructible
      is_trivially_destructible
      is_nothrow_destructible      		 (C++11)
      (C++11)
      (C++11)
      has_virtual_destructor (C++11)
      Les relations et les requêtes de propriété
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      Relationships and property queries
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      is_same (C++11)
      is_base_of (C++11)
      is_convertible (C++11)
      alignment_of (C++11)
      rank (C++11)
      extent (C++11)
      Modifications de type
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      Type modifications
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      remove_cv
      remove_const
      remove_volatile      		 (C++11)
      (C++11)
      (C++11)
      add_cv
      add_const
      add_volatile      		 (C++11)
      (C++11)
      (C++11)
      make_signed (C++11)
      make_unsigned (C++11)
      Transformations de type
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      Type transformations
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      aligned_storage (C++11)
      aligned_union (C++11)
      decay (C++11)
      enable_if (C++11)
      conditional (C++11)
      common_type (C++11)
      underlying_type (C++11)
      result_of (C++11)
      Tapez constantes traits
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      Type trait constants
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      integral_constant (C++11)
       
      Déclaré dans l'en-tête <cstddef>
      #define offsetof(type, member) /*implementation-defined*/
      offsetof la macro s'étend à une constante de std::size_t type, la valeur de ce qui est le décalage en octets du début d'un objet du type spécifié à son élément de donnée, y compris le cas échéant rembourrage .
      Original:
      The macro offsetof expands to a constant of type std::size_t, the value of which is the offset, in bytes, from the beginning of an object of specified type to its specified member, including padding if any.
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      Sommaire

      [modifier]Notes

      Si type n'est pas un type standard mise en page, le comportement est indéfini .
      Original:
      If type is not a standard-layout type, the behavior is undefined.
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      Si member est un membre statique ou un membre de la fonction, le comportement est indéfini .
      Original:
      If member is a static member or a function member, the behavior is undefined.
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      Le décalage du premier membre d'un type standard-layout est toujours zéro (vide de base de l'optimisation est obligatoire)
      Original:
      The offset of the first member of a standard-layout type is always zero (vide de base de l'optimisation is mandatory)
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      [modifier]Mise en œuvre possible

      #define offsetof(type,member) ((std::size_t) &(((type*)0)->member))

      [modifier]Exemple

      #include <iostream>#include <cstddef>struct S {char c;double d;};int main(){std::cout<<"the first element is at offset "<< offsetof(S, c)<<'\n'<<"the double is at offset "<< offsetof(S, d)<<'\n';}

      Résultat : 

      the first element is at offset 0 the double is at offset 8

      [modifier]Voir aussi

      unsigned integer retournée par l'opérateur sizeof
      Original:
      unsigned integer type returned by the sizeof operator
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      (typedef)[edit]
      (C++11)
      vérifie si un type est standard disposition type
      Original:
      checks if a type is standard-layout type
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      (classe générique)[edit]
      Récupérée de « https://fr.cppreference.com/mwiki/index.php?title=cpp/types/offsetof&oldid=49661 »
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