redef fun compile_header_structs do
		self.header.add_decl("typedef void(*nitmethod_t)(void); /* general C type representing a Nit method. */")
		self.compile_header_attribute_structs
		self.header.add_decl("struct class \{ int box_kind; nitmethod_t vft[]; \}; /* general C type representing a Nit class. */")

		# With resolution_table_table, all live type resolution are stored in a big table: resolution_table
		self.header.add_decl("struct type \{ int id; const char *name; int color; short int is_nullable; const struct types *resolution_table; int table_size; int type_table[]; \}; /* general C type representing a Nit type. */")
		self.header.add_decl("struct instance \{ const struct type *type; const struct class *class; nitattribute_t attrs[]; \}; /* general C type representing a Nit instance. */")
		self.header.add_decl("struct types \{ int dummy; const struct type *types[]; \}; /* a list types (used for vts, fts and unresolved lists). */")
		self.header.add_decl("typedef struct instance val; /* general C type representing a Nit instance. */")

		if not modelbuilder.toolcontext.opt_no_tag_primitives.value then
			self.header.add_decl("extern const struct class *class_info[];")
			self.header.add_decl("extern const struct type *type_info[];")
		end
	end

	# Declaration of structures the live Nit types
	# Each live type is generated as an independent C `struct` type.
	# They only share a common first field `classid` used to implement the polymorphism.
	# Usualy, all C variables that refers to a Nit object are typed on the abstract struct `val` that contains only the `classid` field.
	redef fun compile_header_structs do
		self.header.add_decl("typedef struct \{int classid;\} val; /* general C type representing a Nit instance. */")
	end

	redef fun compile_header_structs do
		self.header.add_decl("typedef void(*nitmethod_t)(void); /* general C type representing a Nit method. */")
		self.compile_header_attribute_structs
		self.header.add_decl("struct class \{ int id; const char *name; int box_kind; int color; const struct vts_table *vts_table; const struct type_table *type_table; nitmethod_t vft[]; \}; /* general C type representing a Nit class. */")
		self.header.add_decl("struct type_table \{ int size; int table[]; \}; /* colorized type table. */")
		self.header.add_decl("struct vts_entry \{ short int is_nullable; const struct class *class; \}; /* link (nullable or not) between the vts and is bound. */")
		self.header.add_decl("struct vts_table \{ int dummy; const struct vts_entry vts[]; \}; /* vts list of a C type representation. */")
		self.header.add_decl("typedef struct instance \{ const struct class *class; nitattribute_t attrs[1]; \} val; /* general C type representing a Nit instance. */")
	end