CODEWITHSUNDEEP
c
daniel flores
daniel flores

Reputation: 13

*** stack smashing detected ***: terminated Aborted

I am trying to create a program that allows me to enter grades for a number of students (between 1-25). For each student, I am suppose to enter a number of grades (between 1-10). For each student I am supposed to supply their first and last name, age, and grade average depending on the number of grades I enter. This is for an assignment, so I am required to have a struct in my program named Info, and inside, it has the char variables firstName and lastName, int variable age, and float variable average.

#include <stdio.h> 
int gradeVar;
int studVar;       
struct Info {
    char firstName[20];
    char lastName[20];
    int age;
    int Exam;  //This is for something I planned to add later
    float Average;
};

int main() {
printf("How many students will you grade (1-25)? ");
     
     
    scanf("\n%i", &studVar);
    if (studVar<1 || studVar>25) {
        do{                                                
        printf("Invalid\n");                               
        printf("How many students will you grade (1-25)? ");
    scanf("\n%i", &studVar);
        } while (studVar<1 || studVar>25);
    }


printf("How many grades will you read per student (1-10)? ");       
    scanf("\n%i", &gradeVar);
    if(gradeVar<1 || gradeVar>10) {
        do{
            printf("Invalid\n");
            printf("How many grades will you read per student (1-10)? ");  
            scanf("\n%i", &gradeVar);                                      
        } while(gradeVar<1 || gradeVar>10);
    }
    
    struct Info Student[studVar];  
                                   
    for(int n=1; n <= studVar; ++n) {             
                                  
        printf("Enter First Name for student %i: ", n);
        scanf("\n%s", Student[n].firstName);
        printf("Enter Last Name for student %i: ", n);
        scanf("\n%s", Student[n].lastName);

//Every thing worked fine until I added the last two lines below//
        printf("Enter age for student %i: ", n);
        scanf("\n%d", &Student[n].age);
    };

    return 0;
}

It is until I add the last two lines:

printf("Enter age for student %i: ", n);
        scanf("\n%d", &Student[n].age);

That I got error in my output saying stacked smashing

enter image description here

I am not entirely sure why this is happening, and don't know where to fix it so that it runs the way I want it to. If you anyone can clarify this for me I'd appreciate it.

Upvotes: 1

Views: 1030

Answers (2)

paxdiablo
paxdiablo

Reputation: 881113

In C, when you declare struct Info Student[studVar];, the valid indexes for that array are zero through studVar - 1, not 1 through studVar.

Hence your scanf statements inside the loop should be using n - 1 rather than n. Your problems is that, when you enter 2 for the number of students, that gives you Student[0] and Student[1].

Trying to write to Student[2].id is going to result in undefined behaviour such as, hmmm, ..., stack smashing I guess :-)

Upvotes: 3

Joshua
Joshua

Reputation: 43188

Expected:

for(int n=0; n < studVar; ++n)

Got:

for(int n=1; n <= studVar; ++n)

Arrays are 0 based not 1 based.

There's another overflow waiting for you if you exceed 19 characters in a name component.

Upvotes: 2

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