Thread: realloc segfaults.

Are you sure you are needing to use realloc, is this some realloc exercise? As calling this over and over for each new student roll to be entered is costly.

I would prefer you change over to strictly using an array for this and is much faster to insert.

Code:

 StdInfo students[10];

...

 do
    {
      printf ("Enter Roll of Student %d :\t", i);
      scanf ("%d", &(students[i++].roll));
      printf ("\n\nEnter another ? (1/0):\t");
      scanf ("%d", &s);
    }
  while (s == 1);

Remove your realloc and any malloc calls, you do no need them then!


Then do double check that they have been inserted try something like this:

Code:

  int z = 0;

  for (; z < i; z++)
    {
      printf ("Students rolls are:  student %d, roll = %d\n", z,
              students[z].roll);
    }

Originally Posted by slingerland3g

Are you sure you are needing to use realloc, is this some realloc exercise?

You can assume something like this.I was showing some of my friends about when we might need to use realloc. suddenly I got stuck and more than 8 hours past still trying to find the answer. I must solve it by using malloc and realloc only.

Originally Posted by iMalc

The OP has already been told that he can't scanf into a short, here: http://www.gamedev.net/community/for...opic_id=515880

Currently there is no short in my code I've changed all of them to normal int

What Dino said. Your variable assignment for

Code:

 unsigned short int s = 1

should be

Code:

int s = 1;

Originally Posted by slingerland3g

What Dino said. Your variable assignment for

Code:

 unsigned short int s = 1

should be

Code:

int s = 1;

Ya I've already done it and it gives the same result no change.
Well this is my current code.

Code:

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

struct StudentInfo{
	//char* name;
	unsigned int roll;
};

typedef struct StudentInfo StdInfo;

int main(int argc, char** argv){
	StdInfo* students;
	unsigned int size = 3, i=0, j;
	int s = 1;
	char* dump_name;

	students = malloc( size*sizeof(StdInfo) );

	do{
		//StudentInfo.name removed

		printf("Enter Roll of Student %d :\t", i);
		//fflush(stdin);
		int dmp_roll;
		scanf("%d\n", &dmp_roll);
		students[i].roll = dmp_roll;
		printf("\n\nEnter another ? (1/0):\t");
		//fflush(stdin);
		scanf("%d\n", &s);
		//fflush(stdin);
		if(s == 1){
			size += 1;
			void* dump = realloc( students, size*sizeof(StdInfo) );
			if(dump != 0x0){
				students = dump;
			}else{
				printf("realloc Failed\n");
				return 2;
			}
		}
		i++;
	}while(s == 1);

	free(students);
	students = 0x0;

	return 0;
}

It also makes scanf problem.

Originally Posted by brewbuck

Doubling the size of the array on each entry will make it exceed 4 gigabytes within 32 iterations...

I've already changed it to size += 1 So its not doubling the size.