Segmentation Fault 11 with code blocks

Question

I've been having some trouble with a program I'm making. Every time I try to compile it, I keep getting Segmentation Fault 11. I don't know why this is happening. I'm using Code Block IDE and whenever I Build and run, segmentation fault 11 continues to arise. Any ideas on how I can remedy this?

#include <stdio.h> #define NUMTEMPS 2881 int main(void){ //opening the file with temperatures FILE * ifp; ifp = fopen("temp.txt", "r"); //Declaring variables int i,j; int pct, num30 = 0, count_ac_h = 0, count_ac_t = 0, current_h = 0; int ac_on = 0, count_ac = 0; double temps[2881], pct_hr[24], diff, current_temp, previous_temp; //Checking the temperature from the .txt file and counting the occurences for (i = 0; i < 2881; ++i){ fscanf(ifp, "%lf", &temps[i]); } previous_temp = temps[0]; for (i = 0; i < 2881; ++i){ if (num30 == 120){ count_ac_t += count_ac_h; pct_hr[current_h] = (double)(count_ac_h/120); current_h++; count_ac_h = 0; num30 = 0; } current_temp = temps[i]; diff = previous_temp - current_temp; if(diff > -0.5 && diff <0.5){ if(ac_on == 1){ count_ac_h++; } } else if (diff <= -0.5){ if (ac_on == 0){ ac_on = 1; count_ac_h++; } } else if (diff >= 0.5){ if(ac_on == 1) ac_on = 0; } num30++; previous_temp = current_temp; } // Creating the bar graph based on results from above double pct_day = (double)(count_ac/NUMTEMPS); for (i = 20; i >= 0; i--){ pct = i*5; for (j = 0; j < 24; ++j){ if (pct > (pct_hr[j]*100)) printf("_"); else printf("*"); } printf("\n"); } return 0; }

Run it under a debugger, it should tell you where (and why) it is crashing. Segmentation faults are typically due to using bad pointers. — vonbrand
– vonbrand, Commented Mar 19, 2014 at 19:16
Why #define NUMTEMPS to be 2881 and then continue to use the literal all over your code? Just use NUMTEMPS! — Two-Bit Alchemist
– Two-Bit Alchemist, Commented Mar 19, 2014 at 19:16
I would use gdb if you're on linux. If you run it there it'll tell you the exact line where you segfault. — dbeer
– dbeer, Commented Mar 19, 2014 at 21:22

LearningC · Accepted Answer · 2014-03-19 19:20:50Z

for (i = 20; i >= 0; i--){ pct = i*5; for (i = 0; i < 24; ++i){ if (pct > (pct_hr[j]*100)) printf("_"); else printf("*"); }

check this loop, use different loop variables for nested loops. here j is uninitialized so if it takes random large value it will result is segmentation fault.

@user3230393 ok. dont make changes to question to reflect the suggestions from answer. it makes the answer irrelevant. so roll back your question to original state.

Søren Debois · Accepted Answer · 2014-03-19 19:22:17Z

This line:

pct_hr[current_h] = (double)(count_ac_h/120);

How can you be sure current_h is never greater than 23?

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