How to fix segmentation fault for while loop in c - c

Question

I'm working on an assignment and trying to write the code to answer this question:
Write a program that computes the total weight of a cargo. The user has many types of boxes (numbered 1 to n). For each box type, the program asks the user about the weight and quantity. The program thencomputes and prints the total cargo weight.
In the output sample below, the user has three box types. For box type 2, the user enters the sentinel -1 to
indicate they’re done with the input. Your program should print Type 1, 2, 3, etc. as shown in the
output below.
Enter weight (lbs) of Type 1 box: 4
Enter quantity: 2
Enter weight (lbs) of Type 2 box: -1
The total weight is 8 lbs.
When i run this code it runs the first line to input weight but then gives me a segmentation fault and says (core dumped). -1 is the sentinel and even when the enter weight is inside the while loop the result is the same. What am I doing wrong? I'm sorry I'm new to C
#include <stdio.h>
int main()
{
int weight; //weight of boxes
int quantity; //number of boxes
int total_weight; //total weight
int n = 1;
printf("Enter weight (lbs) of Type %d box: ", n);
scanf("%d", weight);
while(weight!=-1) //Iterate loop until w=-1
{
printf("Enter quantity: \n");
scanf("%d", quantity);
total_weight= total_weight + (quantity*weight);
n++;
}
printf("The total weight is %0.2d", total_weight);
return 0;
}

Answer 1

This is not how you use scanf
scanf("%d", weight);
scanf("%d", quantity);
You should pass the address of the variable, not the value of the variable.
That would look like this:
scanf("%d", &weight);
scanf("%d", &quantity);
Your while loop depends on value weight. The value of weight never changes in your loop, so the loop can never exit.
This line:
total_weight= total_weight + (quantity*weight);
uses the value of total_weight, which was never initialized.
You should initialize your variables.
All in all, I think your fixed code should look like:
#include <stdio.h>
int main()
{
int weight = 0; //weight of boxes
int quantity = 0; //number of boxes
int total_weight = 0; //total weight
int n = 1;
while(weight!=-1)
{
printf("Enter weight (lbs) of Type %d box: ", n);
scanf("%d", &weight); // Update weight **inside** the loop
printf("Enter quantity: \n");
scanf("%d", &quantity);
total_weight= total_weight + (quantity*weight);
n++;
}
printf("The total weight is %0.2d", total_weight);
return 0;
}

Answer 2

while(weight!=-1) //Iterate loop until w=-1
{
printf("Enter quantity: \n");
scanf("%d", quantity);
total_weight= total_weight + (quantity*weight);
n++;
}
Problem is in while condition, weight never change it's value so the condition always true so infinite loop.
Fix this statement scanf("%d", &weight);

Answer 3

Your problem is you are trying to assign a value to the pointer of quantity and weight, instead you need to put &quantity and &weight also you do not have another input for the weight, you should also use a do while instead of a while loop. It should look like this
#include <stdio.h>
int main()
{
int weight; //weight of boxes
int quantity; //number of boxes
int total_weight; //total weight
int n = 1;
do
{
printf("Enter weight (lbs) of Type %d box: ", n);
scanf("%d", &weight);
printf("Enter quantity: \n");
scanf("%d", &quantity);
total_weight= total_weight + (quantity*weight);
n++;
}while (weight != -1);
printf("The total weight is %0.2d", total_weight);
return 0;
}