Thread: segfaulting!

Originally Posted by CMakesMeSad :(

Ah sorry, it was originally:

Code:

scanf("%d", &messages[position].priority);

I did take your advice the first time, i was just messing around with different things since I couldnt even get the simple one to work

ask yourself, what is the value of position

I would recommend starting with a fixed-size structure and no dynamic allocation first, until you have got everything else worked out.

Hey everyone, Ive been working on this all day and have made some good progress, however Im stuck again. Im working on the option of listing the messages by priority. However, no matter what priority I enter, it will only list the first message i enter.

Code:

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#define MAX 100

struct MSG {
	int priority;
	int destination;
	char *message;
	int length;
	struct MSG *nextPtr;
}*node, *t;

typedef struct MSG message;


void add(struct MSG **n, int priority1, int destination1, char *message1);

int main ()
{
	struct MSG *temp;
	int choice;
	int num1, num2;
	char text[MAX];
 		
do
{
	printf("1.) Quit\n");
	printf("2.) Transmit next message\n");
	printf("3.) List messages by priority\n");
	printf("4.) Summarize message list\n");
	printf("5.) Add new message\n");
	printf(":");
	scanf("%d", &choice);
	switch(choice){

		case 1:
			return 0;
		case 2:
			//transmit next message
			if (node==NULL)
			{
				printf("No messages left!\n");
				break;
			}
			
			else
			{
				temp=node;
				while(temp != NULL)
				{
					printf("%d", temp -> priority);
					printf("%dn", temp -> destination);
					char *loc=(char *) malloc (strlen(temp -> message));
					strcpy(loc, temp -> message);
					printf("%s", loc);
					free(loc);
					temp=temp -> nextPtr;
				}
				printf("test=%d %d %s\n", t-> priority, t-> destination, t-> message);
			}


			break;
		case 3:
			//list messages by priority
				printf("Enter priority of the messages you would like to retrieve:\n");
				scanf("%d", &pnum);
				
				temp=node;
				while(temp != NULL)
				{
					//printf("%d", temp -> priority);
					//printf("%dn", temp -> destination);
					char *loc=(char *) malloc (strlen(temp -> message));
					strcpy(loc, temp -> message);
					//printf("%s", loc);
					free(loc);
					temp=temp -> nextPtr;
					if (t -> priority == pnum)
					{
						printf("%d %d %s\n", t -> priority, t -> destination, t -> message);
					}
				}


			break;
		case 4:
			//summarize message list
			break;
		case 5:
			//add new message
			printf("Enter priority, destination and message:");
			scanf("%d%d", &num1, &num2);
			fgets(text, MAX, stdin);
			add(&node, num1, num2, text);	
			break;
		default:
			printf("Invalid entry, please try again.\n");
			break;
	}
}while (choice <= 5);

	return 0;
}





void add(struct MSG **n, int priority1, int destination1, char *message1)
{
	struct MSG *temp, *node1;
	
	if(*n==NULL)
	{
		temp=(struct MSG *) malloc (sizeof(struct MSG));
		temp -> priority = priority1;
		temp -> destination=destination1;
		temp -> message=(char *) malloc (strlen(message1)+1);
		strcpy(temp -> message, message1);
		temp -> nextPtr=NULL;
		*n=temp;
		t=temp;
		printf("test=%d %d %s\n", t->priority, t->destination, t->message);
	}

	else
	{
		temp=*n;
		while(temp->nextPtr != NULL)
			temp=temp -> nextPtr;
		node1 = (struct MSG *) malloc(sizeof(struct MSG));
		node1 -> priority=priority1;
		node1 -> destination=destination1;
		node1 -> message=(char*) malloc(strlen(message1)+1);
		strcpy(node1 -> message, message1);
		node1 -> nextPtr = NULL;
		temp -> nextPtr = node1;
	}

}

You aren't printing anything other than the exact priority match. Is that what you want?

Quzah.

Code:

for( t = list; t; t = t->next )
{
    if( t->priority == tofind )
    {
        printf("%d %d %s\n", t-> priority, t-> destination, t-> message);
    }
}

Should be fine, assuming your list actually isn't broken somehow. You should consider just displaying the whole list first, to make sure that actually works (basically the above loop, except don't bother checking priority).


Quzah.