When nesting structures, the compiler needs to recognize the struct type you intend to use as a member. This can either be by giving a full declaration of the struct (show in in the example) or by providing a forward declaration only, assuming that a full declaration is provided at a different location.
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/** * File: car_return.c * Author: Risto Heinsar * Created: 02.02.2015 * Modified 31.01.2025 * * Description: This is an example code showing creation of a nested struct */ #include <stdio.h> #include <string.h> #define REG_LEN 8 #define FIELD_LEN 32 typedef struct Vehicle { char make[FIELD_LEN]; char model[FIELD_LEN]; } Vehicle; typedef struct CarRegistryEntry { char regNum[REG_LEN]; char regCity[FIELD_LEN]; char owner[FIELD_LEN]; int year; Vehicle car; } CarRegistryEntry; void PrintCar(CarRegistryEntry motor); void PrintCarUsingPtr(CarRegistryEntry *car); int main(void) { CarRegistryEntry indestructibleHilux; strcpy(indestructibleHilux.regNum,"E473CJN"); strcpy(indestructibleHilux.regCity,"London"); strcpy(indestructibleHilux.owner,"The Stig"); indestructibleHilux.year = 1988; strcpy(indestructibleHilux.car.make,"Toyota"); strcpy(indestructibleHilux.car.model,"Hilux"); PrintCar(indestructibleHilux); PrintCarUsingPtr(&indestructibleHilux); return 0; } /** * Description: Outputs the details of an automobile using . notation * * Parameters: motor, vehicle structure with the details of a car * * Return: none */ void PrintCar(CarRegistryEntry motor) { printf("%s %s, reg number %s, belongs to %s and is registered in %s\n", motor.car.make, motor.car.model, motor.regNum, motor.owner, motor.regCity); } /** * Description: Outputs the details of an automobile using -> notation * * Parameters: motor, vehicle structure with the details of a car * * Return: none */ void PrintCarUsingPtr(CarRegistryEntry *motor) { printf("%s %s, reg number %s, belongs to %s and is registered in %s\n", motor->car.make, motor->car.model, motor->regNum, motor->owner, motor->regCity); } |