Why do I have a segmentation fault in this C programing code?

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I'm trying to program simple mergesort problem with C language.
but I still have segmentation fault and I'm stuck in it. PLEASE HELP...!

What I have tried:

C++

#include <stdio.h>
#include <stdlib.h>

void merge(int *arr, int start, int mid, int end)
{
	int i, j, k;
	int arrsize=end-start+1;
	int sm_size=mid-start+1;
	int me_size=end-mid+1;
	
	for(i=0; i < arrsize; i++)
        {
            if(j < sm_size && k < me_size)
                if(*(arr+start+j) > *(arr+mid+k))
			{
				*(arr+i) = *(arr+start+j);
				j++;
			}
			
			else
			{
				*(arr+i) = *(arr+mid+k);
				k++;
			}
		}
		
		else if(j

Posted 5-Nov-16 18:03pm

Member 12834752

Updated 5-Nov-16 21:26pm

Richard MacCutchan

v6

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Comments

Richard MacCutchan 6-Nov-16 3:27am

Your code is incomplete, but if you look at what you do have above, you are using the variables i, j and k without initialising them so this will never work.

Albert Holguin 8-Nov-16 13:15pm

You're doing so much pointer arithmetic that you're likely going out of bounds. Use a debugger or put some print statements to figure out where you're going out of bounds.

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Patrice T · Answer 1 · 2016-11-05T19:14:00

You should think about initializing j and k before using them.
I fear you need to learn the debugger quickly because on first look your program will kill a part of the values to sort. If I remember well, the merge is not done in same array.

You should learn to use the debugger as soon as possible. Rather than guessing what your code is doing, It is time to see your code executing and ensuring that it does what you expect.

The debugger allow you to follow the execution line by line, inspect variables and you will see that there is a point where it stop doing what you expect.
Debugger - Wikipedia, the free encyclopedia[^]
Mastering Debugging in Visual Studio 2010 - A Beginner's Guide[^]

The debugger is here to show you what your code is doing and your task is to compare with what it should do.
When the code don't do what is expected, you are close to a bug.

Advice: take a sheet of paper and try to do it by hand, your program should use the same procedure.