C seg fault - where/what? - c

Question

I have this program that is supposed to handle assigning seats to passengers.
I cannot figure out what is causing my seg fault. I am using an array of structs and that may be where the problem is coming from.
I think its probably a problem with dereferencing some struct members, but I can't find where.
Here is my code:
struct seat
{
// Max Name of 32 chars
char name[32];
// Seat Number
int sNum;
// Seat taken = 1, open = 0
int taken;
};
// Function headers
void seat(struct seat plane[][10]);
void mani(struct seat plane[][10]);
void pass(int seat, char name[], int class);
int main()
{
// My airline plane is 6 seats per row, 10 rows
// Row 1/2 are First Class
// Row 3/4 are Business Class
// Init counter variables to keep track of the number
// of First Class/Business seats already taken
// also the user input var
int input, ticketin, class1 = 0, class2 = 0, class3=0, sNum, i;
char namein[32];
// Vars for pass function
char passname[32];
int passclass;
int passseat;
// Init a 2d array 6 colums 10 rows
struct seat plane[6][10];
for (i=0; i<sizeof(plane); i++)
{
plane[i]->sNum = i+1;
plane[i]->taken = 0;
}
// Begin user input loop
// Menu with 3 options:
// Display the seating chart, indicating taken seats
// Display the manifest
// Display a boarding pass - seat number, name, class
do
{
do
{
// Prompt user for ticket selection
printf("Please type 1 for \"First Class\"\n");
printf("Please type 2 for \"Business Class\"\n");
printf("Please type 3 for \"Economy Class\"\n");
scanf(" %d", &ticketin);
// Check for valid input
if (ticketin == 1)
{
// Check to make sure first class is not full
if (class1 < 12)
{
class1 += 1;
printf("First class is open!\n");
} else {
printf("First class is full, please choose another class\n");
}
} else if (ticketin == 2)
{
// Check to make sure business class is not full
if (class2 < 12)
{
class2 += 1;
printf("Business class is open!\n");
} else {
printf("Business class is full, please choose another class\n");
if (class1 < 12)
{
printf("Upgrade to First Class by entering 1");
}
}
} else if (ticketin == 3)
{
// Check to make sure business class is not full
if (class3 < 12)
{
class3 += 1;
printf("Economy class is open!\n");
} else
{
printf("Economy class is full, please choose another class\n");
if (class1 < 12)
{
printf("Upgrade to First Class by entering 1");
}
if (class2 < 12)
{
printf("Upgrade to Business Class by entering 2");
}
}
} else
{
ticketin = 4;
}
// Prompt the user for their name
printf("Please input your name:\n");
scanf(" %s", namein);
} while (ticketin == 4);
// Handle loading the new passenger into plane array
switch (ticketin)
{
case 1:
for (i=0; i<12; i)
{
if (plane[i]->taken == 0)
{
plane[i]->taken = 1;
strcpy(plane[i]->name, namein);
sNum = plane[i]->sNum;
} else
{
i++;
}
}
case 2:
for (i=12; i<24; i)
{
if (plane[i]->taken == 0)
{
plane[i]->taken = 1;
strcpy(plane[i]->name, namein);
sNum = plane[i]->sNum;
} else
{
i++;
}
}
case 3:
for (i=24; i<60; i)
{
if (plane[i]->taken == 0)
{
plane[i]->taken = 1;
strcpy(plane[i]->name, namein);
sNum = plane[i]->sNum;
} else
{
i++;
}
}
}
printf("Menu Options: \n");
printf("(1) Display the seating chart\n");
printf("(2) Display the passenger manifest\n");
printf("(3) Display a boarding pass\n");
printf("(4) Quit\n");
// Prompt user for their selection
printf("Please enter your menu selection:\n");
scanf(" %d", &input);
// Switch case handling function calls
switch (input)
{
case 1:
seat(plane);
break;
case 2:
mani(plane);
break;
case 3:
printf("Please input a seat number\n");
scanf(" %d", &passseat);
if (passseat < 12)
{
passclass = 1;
} else if (passseat < 24)
{
passclass = 2;
} else
{
passclass = 3;
}
pass(passseat, plane[passseat-1]->name, passclass);
break;
default:
printf("invalid menu option or quitting\n");
break;
}
} while (input != 4);
}
// Display seating chart function
void seat(struct seat plane[][10])
{
int i, sNum;
for (i=0; i<sizeof(plane); i++)
{
if (plane[i]->taken == 1)
{
printf("Seat %d is taken\n", i++);
} else
{
printf("Seat %d is not taken\n", i++);
}
}
}
// Display Manifest function
void mani(struct seat plane[][10])
{
int i;
for (i=0; i<sizeof(plane); i++)
{
if (plane[i]->taken == 1)
{
printf("Passenger %s in seat %d\n", plane[i]->name, i++);
}
}
}
// Display boarding pass function
void pass(int seat, char name[], int class)
{
printf("Boarding pass for %s\n", name);
printf("Seat Number: %d\n", seat);
switch (class)
{
case 1:
printf("First Class");
break;
case 2:
printf("Business Class");
break;
case 3:
printf("Economy Class");
break;
}
}

Answer 1

There are probably other errors, but this is the most obvious one:
for (i=0; i<sizeof(plane); i++)
{
plane[i]->sNum = i+1;
plane[i]->taken = 0;
}
sizeof(plane) is the number of bytes in the plane array. This is 10 * 6 * sizeof(struct seat), so you're writing way outside the array. If you want to know the number of elements in an array, you have to divide the size of the array by the size of an array element:
for (i=0; i<sizeof(plane)/sizeof(*plane); i++)
{
plane[i]->sNum = i+1;
plane[i]->taken = 0;
}
But your code is only initializing the first element in each row of the array.
Since it's a 2-dimensional array, you need nested loops. And you should use normal member access with . rather than pointer indirection.
for (i=0; i<sizeof(plane)/sizeof(plane[0]); i++)
{
for (int j = 0; j < sizeof(plane[i])/sizeof(plane[i][0]); j++)
{
plane[i][j].sNum = i+1;
plane[i][j].taken = 0;
}
}
You could simplify all the sizeof stuff by defining macros:
#define ROWS 6
#define COLS 10
and then using these macros in the array declaration and the for loop limits.
Similar changes need to be made in other code that loops over the plane array.