C code, compiler Xcode, detected source and destination buffer overlap - c

Question

I'm doing a project for school in which I have to create a program that plays go fish. In which a deck of cards is in a doubly linked list. I read the cards from a file in the function Addcard. I have a function to print the cards and a function that is supposed to shuffle the cards. I have ot use the parameters of the struct to implement the cards. I sometimes see the error "detected source and destination buffer overlap" when I run the shuffle function, sometimes not. When the error comes up it says Thread 1: signal SIGABRT next to a string copy function. I believe it has something to do with the buffer size of some kind of allocated memory being too small, but I don't really know how to fix it. Any help would be more then appreciated. Here is an excerpt of the code I have written.
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <math.h>
#include <time.h>
typedef struct card_s{
char suit[7];
int value;
struct card_s *next, *previous;
}card;
int rand_gen(int count){
double frac;
frac = (double)rand()/((double)RAND_MAX+1);
return floor(count * frac); //random number in [0, count]
}
void addCard(card *p, card **hl, card **hr, FILE *inp){
card *temp; // pointer to a node_t
temp = (card *)malloc(sizeof (card)); // new node creation
fscanf(inp, "%d", &temp->value);
fscanf(inp, "%s", temp->suit);
if (*hl == NULL){ // if left head is null, i.e., list is empty
temp->previous = NULL;
temp->next = NULL;
*hl = temp;
*hr = temp;
}
else if (p->next == NULL){ // if adding at the end of list
temp->previous = p;
temp->next = NULL;
p->next = temp;
*hr = temp;
}
else{ // if adding to the middle of the list
temp->next = p-> next;
temp->previous = p;
p->next = temp;
temp->next->previous = temp;
}
}
void Print(card **headl) { //this function prints from left to right only
card *temp;
temp = (*headl);
while(temp != NULL) {
printf("|");
printf("%d", temp->value);
if(strcmp(temp->suit,"hea")==0) {
printf("♥");
}
if(strcmp(temp->suit,"clu")==0) {
printf("♣");
}
if(strcmp(temp->suit,"spa")==0) {
printf("♠");
}
if(strcmp(temp->suit,"dia")==0) {
printf("♦");
}
printf("|");
//printf("%s ", temp->suit);
temp = temp->next;
}
}
void Print1(card **headl) { //this function prints from left to right only
card *temp;
temp = (*headl);
while(temp != NULL) {
for(int i = 0; i < 13; i++) {
printf("|");
if(temp->value == 11){
printf("J");
}
else if(temp->value == 12) {
printf("Q");
}
else if(temp->value == 13) {
printf("K");
}
else if(temp->value == 14) {
printf("A");
}
else {
printf("%d", temp->value);
}
if(strcmp(temp->suit,"h")==0) {
printf("♥");
}
if(strcmp(temp->suit,"c")==0) {
printf("♣");
}
if(strcmp(temp->suit,"s")==0) {
printf("♠");
}
if(strcmp(temp->suit,"d")==0) {
printf("♦");
}
printf("|");
//printf("%s ", temp->suit);
temp = temp->next;
}
printf("\n");
}
}
void swap(card *pt, int i, int j) {
card *temp;
temp = (card *)malloc(sizeof(card));
card *temp1 = pt, *temp2 = pt; //creates temperaries that start from the head left
for(int x = 0; x < i; x++) { //counts the number of nodes until i
temp1 = temp1->next;
}
for(int x = 0; x < j; x++) { //counts the number of nodes until j
temp2 = temp2->next;
}
temp->value = temp1->value; //swaps the information not the nodes
strcpy(temp->suit,temp1->suit);
temp1->value = temp2->value;
strcpy(temp1->suit, temp2->suit);
temp2->value = temp->value;
strcpy(temp2->suit, temp->suit);
}
int main(void) {
FILE *inp = NULL;
inp = fopen("cards.txt", "r");
srand((int)time(NULL));
card *headl = NULL, *headr = NULL;
for(int i = 0; i < 52; i++) {
addCard(headr, &headl, &headr, inp);
}
if(inp == NULL) {
printf("No file found");
return -1;
}
printIntro();
printf("\n");
Print1(&headl);
printf("\n");
printf("\n");
for(int i = 0; i <= 45; i++) { //does the swap function swap number times
swap(headl, rand_gen(52), rand_gen(52));
}
Print1(&headl);
return(0);
}

Answer 1

You have an error message saying "detected source and destination buffer overlap", near a string copy function, which copies data from a source to a destination...
Are there any instances of strcpy where the source and dest might point to the same memory?
I see these two lines:
card *temp1 = pt, *temp2 = pt; //creates temperaries that start from the head left
//advance `temp1` `i` times, and `temp2` `j` times
...
strcpy(temp1->suit, temp2->suit);
What happens when i and j are the same value?