Declaring Int variables causes segmentation fault? - c

Question

Hey guys I'm having a really peculiar segmentation fault coming up in my program. This program is suppose to automate the card game "war" and so far I've been able to build two randomized half decks for both players. Which would appear to show that enqueue is working correct. I was also able to dequeue all the values and they appeared in the correct order. However inside main if I uncomment the integer declarations in main the program segfaults every time. I can not for the life of me figure out how simple declarations could cause faults. Please note this is my only second assignment for using queues.
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <string.h>
typedef struct node
{
int value;
int suit;
char*sname;
char*txt;
struct node *next;
} node;
int isempty(node *base){
if (base==NULL)
{return 1;}
else
return 0;
}
void printlist(node *base){
node *current=base;
if(base==NULL)
{
printf("The List is empty!\n");
return;
}
else
{
printf("Content: \n");
int count=0;
while(current!=NULL){
count++;
printf("%s \tof \t%s\n",current->txt,current->sname);
current=current->next;
}
printf("\nCount:%d\n",count);
}
}
char* valname(int n){
char *name;
switch(n)
{
case 0:name="two";break;
case 1:name="three";break;
case 2:name="four";break;
case 3:name="five";break;
case 4:name="six";break;
case 5:name="seven";break;
case 6:name="eight";break;
case 7:name="nine";break;
case 8:name="ten";break;
case 9:name="Jack";break;
case 10:name="Queen";break;
case 11:name="King";break;
case 12:name="Ace";break;
default:printf("Broken\n");exit(1);
}
return(name);
}
char* suitname(int n){
char *name;
switch(n){
case 0:name="Hearts";break;
case 1:name="Spades";break;
case 2:name="Clubs";break;
case 3:name="Diamonds";break;
default:printf("Broken\n");exit(1);
}
return(name);
}
void enqueue(node **base,int item){
node *nn,*current=*base;
nn=malloc(sizeof(node));
if(*base==NULL)
{
*base=nn;
}
else
{
while(current->next!=NULL){
current=current->next;
}
current->next=nn;
}
nn->value=item;
nn->txt=valname(item%13);
nn->sname=suitname(item/13);
nn->next=NULL;
}
int dequeue(node **base){
node *current=*base,*temp;
if (isempty(*base)==0){
int giveback=current->value;
if(current->next==NULL)
{
free(*base);
*base=NULL;
}
else
{
temp=current->next;
free(current);
*base=temp;
}
return giveback;
}else{return -1;}
}
void createdecks(node **deck1,node **deck2){
int i=0;
int thenumber=0;
int deck[52]={0};
for(i=0;i<26;i++){
thenumber=rand()%52;
if(deck[thenumber]==0){
//add to list
enqueue(deck1,thenumber);
deck[thenumber]=1;
}
else
{
i--;
}
}
for(i=0;i<26;i++){
thenumber=rand()%52;
if(deck[thenumber]==0){
//add to list
enqueue(deck2,thenumber);
deck[thenumber]=1;
}
else
{
i--;
}
}
}
int main(void){
node *d1,*d2,*warholder;
//int c1=0,c2=0; //THIS LINE!!!!!!!!!!!
srand(time(NULL));
createdecks(&d1,&d2);
//printlist(d1);
//printlist(d2);
int i=0;
for(i=0;i<26;i++)
printf("%d ",dequeue(&d1)); //return testing
printf("\n");
printlist(d1);
}
Professor's example function
char * namenum( int num)
{
char * name;
switch(num)
{
case 0:
name = "zero"; break;
case 1:
name = "one"; break;
case 2:
name = "two"; break;
case 3:
name = "three"; break;
case 4:
name = "four"; break;
case 5:
name = "five"; break;
case 6:
name = "six"; break;
case 7:
name = "seven"; break;
case 8:
name = "eight"; break;
case 9:
name = "nine"; break;
default:
printf("Invalid Number generated\n");
exit(1);
}
return name;
}

Answer 1

I briefly looked at the code, and it looks to me like you have an uninitialized-variable problem. You declare this in main():
node *d1,*d2,*warholder;
And then you pass it to createdecks(), which in turn calls enqueue(). enqueue() assumes that the pointers are initialized.
Try to initialize d1 and d2 in main():
node *d1,*d2,*warholder;
d1 = d2 = warholder = NULL;

Answer 2

Its not due to declaring int. You have not allocated memory to char *name on several times before using it. for example
char* valname(int n){
char *name;
allocate memory using malloc() before using name after above code
char* suitname(int n){
char *name;
same mistake again
If you want to avoid such situation use array instead of pointer