Thread: Function month_day: Segmentation fault

In theory, the function should work:

Code:

#include <stdio.h>

static char daytab[2][13] = { {0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31},
                                {0, 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31} };

int day_of_year(int year, int month, int day)
{
    int i, leap;
    leap = year%4 == 0 && year%100 != 0 && year%400 == 0;
    for (i = 1; i < month; i++) day += daytab[leap][i];
    return day;
}

void month_day(int year, int yearday, int *pmonth, int *pday)
{
    int i, leap;
    leap = year%4 == 0 && year%100 != 0 || year%400 == 0;
    for (i = 1; yearday > daytab[leap][i]; i++) yearday -= daytab[leap][i];
    *pmonth = i;
    *pday = yearday;
}

int main()
{
    printf("%d\n", day_of_year(2011, 2, 29));
    int day=60, year=2012;
    int *pm, *pd;
    month_day(year, day, pm, pd);
    printf("%d:%d\n", pm, pd);
}

But it produces a segmentation error

Where have you allocated memory for those pointers you're using in main()?

Why are you even using pointers for these variables instead of just using normal non-pointer variables for those values and then passing the address of these variables in the function call?

By the way a decent properly configured compiler should be able to warn you about most of the issues with your program.

Perhaps you meant something more like:

Code:

    int pm, pd;
    month_day(year, day, &pm, &pd);
    printf("%d:%d\n", pm, pd);

Jim

Originally Posted by jimblumberg

Where have you allocated memory for those pointers you're using in main()?

Why are you even using pointers for these variables instead of just using normal non-pointer variables for those values and then passing the address of these variables in the function call?

By the way a decent properly configured compiler should be able to warn you about most of the issues with your program.

Perhaps you meant something more like:

Code:

    int pm, pd;
    month_day(year, day, &pm, &pd);
    printf("%d:%d\n", pm, pd);

Jim

I did not ask to ask me questions, I took this example from the textbook. I read a bad textbook and therefore I need answers and not questions. All problem solved

I did not ask to ask me questions

Why not? If you never have to think about what may be causing the problems then you will never learn to solve these kind of simple problems.

I took this example from the textbook.

So why didn't you state this fact in your first post. I'm not clairvoyant so how should I know anything about the problem other than what you posted.

I read a bad textbook and therefore I need answers and not questions.

So maybe the real answer is for you to talk to your instructor about the "failings" of your textbook. Since you're a beginner what makes you think that the textbook is so bad? Perhaps you misunderstood the point of the code you posted? Perhaps that code is intended bad code designed to illustrate some point made in the text of the book. Without knowing anything about the book I would take your "bad textbook" complaint with some skepticism.

Jim

Originally Posted by Super-Man

I did not ask to ask me questions, I took this example from the textbook. I read a bad textbook and therefore I need answers and not questions. All problem solved

You are (still) retarded.