The C language struct is used as a parameter and a return value

Scenario One: The struct variable is used as a parameter to pass the value.

The compiler needs to copy without affecting Origin value, using the member operator (.). Direct access

/*********************************************************************** All rights reserved (C), Wang Maochun. * * File name: travel.cpp* file ID: None * Content Summary: Main demo struct as parameter and return value * Other Description: "Pass Value" * Current version: v1.0* Author: Wang maochun* finish Date: 2017.7.23************ ***********************************************************/#include<iostream>structtravel_time{inthours; intmins;};Const intMINS_PER_HR = -; Travel_time sum (travel_time t1,travel_time T2);voidshow_time (Travel_time t);intMain () {using namespacestd; Travel_time Day1= {5, $};//5 hours minutesTravel_time Day2 = {4, -};//4 housr minutesTravel_time Trip=sum (day1,day2); cout<<"two-day Total:";        Show_time (Trip); Travel_time Day3= {4, +}; cout<<"three-day Total:";         Show_time (sum (trip,day3)); return 0;}        Travel_time sum (travel_time t1,travel_time T2) {Travel_time total; Total.mins= (t1.mins + t2.mins)%mins_per_hr; Total.hours= (t1.hours + t2.hours) + (T1.mins + t2.mins)/mins_per_hr; returnTotal ;}voidshow_time (Travel_time t) {using namespacestd; cout<< t.hours <<"hours,"<< T.mins <<"minutes\n";} 

Operation Result:

Scenario Two: The struct pointer is used as a parameter to pass the address.

The compiler does not need a copy, and the main function takes the same address. To not affect Origin value, use the const modifier

Use pointers to structural gymnastics (-) indirect access

/*********************************************************************** All rights reserved (C), Wang Maochun. * * File name: travel.cpp* file ID: None * Content Summary: Main demo struct as parameter and return value * Other Description: "Address" * Current version: v1.0* Author: Wang maochun* finish Date: 2017.7.23*********** ************************************************************/#include<iostream>structtravel_time{inthours; intmins;};Const intMINS_PER_HR = -; Travel_time sum (travel_time* t1,travel_time*T2);voidShow_time (travel_time*t);intMain () {using namespacestd; Travel_time Day1= {5, $};//5 hours minutesTravel_time Day2 = {4, -};//4 housr minutesTravel_time Trip= SUM (&day1,&day2); cout<<"two-day Total:"; Show_time (&Trip ); Travel_time Day3= {4, +}; cout<<"three-day Total:"; Travel_time Trip1=sum (&trip,&day3); Show_time (&(TRIP1)); return 0;} Travel_time sum (travel_time* t1,travel_time*T2)        {Travel_time total; Total.mins= (t1->mins + t2->mins)%mins_per_hr; Total.hours= (t1->hours + t2->hours) + (T1->mins + t2->mins)/mins_per_hr; returnTotal ;}voidShow_time (travel_time*t) {    using namespacestd; cout<< t->hours <<"hours,"<< T->mins <<"minutes\n";} 

The result is the same as the scenario one.

The error that occurred:

show_time (sum(&day1,&day2)); Taking address of temporary fpermissive error occurs when this is written.
The reasons are:
Your Middle result which is a temporary variable since it'll disappear
If you assign the result of sum (&day1,&day2) to a variable then it'll no longer be a temporary and you can then Take the address of it.
Therefore, you cannot take an address on a temporary variable that is not assigned a value

The C language struct is used as a parameter and a return value