Sato Sato - 21 days ago 8
C Question

strcpy() not working on some strings but not others

I'm trying to write a simple text adventure program in C. I'm having an issue with strcpy() when trying to set the name/description of each room in the game (see room_setup()). It sets the name/description for every room except for the first two (NO_ROOM and KITCHEN).

#include <stdio.h>
#include <stdbool.h>
#include <string.h>
#include <ctype.h>

#define DIRS 4
#define DEBUG 0
#define MAX_INPUT_LENGTH 100

// defines numeric values for each direction
typedef enum {NORTH, EAST, SOUTH, WEST} en_dirs;

// defines numeric values for each room
typedef enum {
KITCHEN,
PANTRY,
HALLWAY_1,
HALLWAY_2,
TROLLS_DOMAIN,
EMPTY_ROOM_1,
EMPTY_ROOM_2,
EXIT,
NO_ROOM
} en_rooms;

// defines numeric values for each item
typedef enum{
APPLE,
KEY,
NO_ITEM
} en_items;

// defines a struct type to store room data
typedef struct room{
char name[100];
char desc[100];
en_dirs around[DIRS];
} Room;

// defines a struct type to store item data
typedef struct items{
char name[100];
char desc[100];
} Item;

void str_read(char *s); // read string from console, point s to it
void str_upper(char *s); // convert string to upper case
void room_setup(Room *r); // fill info about rooms into r array
void item_setup(Item *i); // fill info about items into i array

int main(void){
char input[MAX_INPUT_LENGTH];
char *verb, *noun;

// arrays to store room and item info. NO_**** is always the final element
// in their respective enums, so the size of the array will never be larger
// than necessary.
Room rooms[NO_ROOM];
Item items[NO_ITEM];

room_setup(rooms); // fill rooms array with info
item_setup(items); // fill items array with info

en_rooms currentRoom = KITCHEN; // set the starting room to the kitchen

// main game loop
while(1){

// print current room name + description
printf("-- %s --\n", rooms[currentRoom].name);
printf("%s\n", rooms[currentRoom].desc);

printf("\n> ");

// read input and convert it to upper case
str_read(input);
str_upper(input);

if(DEBUG){
printf("Input: %s\n", input);
printf("Length: %d\n", strlen(input));
}

// split input into two pieces (expects max of two words, for now)
verb = strtok(input, " ");
noun = strtok(NULL, " ");

if(DEBUG){
printf("Verb: %s\n", verb);
printf("Noun: %s\n", noun);
}

/*
if(strcmp(input, "NORTH") == 0 && rooms[currentRoom].around[NORTH] != NO_ROOM){
currentRoom = rooms[currentRoom].around[NORTH];
}

*/

}

return 0;
}

// points s to new string. clears stdin if user has input more than
// MAX_USER_INPUT characters.
void str_read(char *s){
fgets(s, MAX_INPUT_LENGTH, stdin); // point s to user input from stdin

// clear extra characters from stdin, if the user has input more than
// MAX_INPUT_LENGTH characters.
if(!strchr(s, '\n')){ // newline does not exist
while(fgetc(stdin) != '\n'); // discard until newline
}
}

// converts string s to upper case
void str_upper(char *s){
int i;
char c;

for(i = 0; i < strlen(s); i++){
s[i] = toupper(s[i]);
}
}

// fills the array r with info on each room.
void room_setup(Room *r){

strcpy(r[NO_ROOM].name, "Nothing there.");
strcpy(r[NO_ROOM].name, "Description");
r[NO_ROOM].around[NORTH] = NO_ROOM;
r[NO_ROOM].around[EAST] = NO_ROOM;
r[NO_ROOM].around[SOUTH] = NO_ROOM;
r[NO_ROOM].around[WEST] = NO_ROOM;

strcpy(r[KITCHEN].name, "Kitchen");
strcpy(r[KITCHEN].desc, "This is the kitchen.");
r[KITCHEN].around[NORTH] = NO_ROOM;
r[KITCHEN].around[EAST] = PANTRY;
r[KITCHEN].around[SOUTH] = NO_ROOM;
r[KITCHEN].around[WEST] = NO_ROOM;

strcpy(r[HALLWAY_1].name, "Hallway");
strcpy(r[HALLWAY_1].desc, "A long hallway.");
r[HALLWAY_1].around[NORTH] = HALLWAY_2;
r[HALLWAY_1].around[EAST] = NO_ROOM;
r[HALLWAY_1].around[SOUTH] = KITCHEN;
r[HALLWAY_1].around[WEST] = TROLLS_DOMAIN;

strcpy(r[TROLLS_DOMAIN].name, "Troll's Domain");
strcpy(r[TROLLS_DOMAIN].desc, "You see a Troll.");
r[TROLLS_DOMAIN].around[NORTH] = NO_ROOM;
r[TROLLS_DOMAIN].around[EAST] = HALLWAY_1;
r[TROLLS_DOMAIN].around[SOUTH] = EMPTY_ROOM_1;
r[TROLLS_DOMAIN].around[WEST] = NO_ROOM;

strcpy(r[EMPTY_ROOM_1].name, "Empty Room");
strcpy(r[EMPTY_ROOM_1].desc , "An empty room. There was no reason to come here.");
r[EMPTY_ROOM_1].around[NORTH] = TROLLS_DOMAIN;
r[EMPTY_ROOM_1].around[EAST] = NO_ROOM;
r[EMPTY_ROOM_1].around[SOUTH] = NO_ROOM;
r[EMPTY_ROOM_1].around[WEST] = NO_ROOM;

strcpy(r[HALLWAY_2].name, "Hallway"); //hallway 2
strcpy(r[HALLWAY_2].desc, "A long hallway.");
r[HALLWAY_2].around[NORTH] = EXIT;
r[HALLWAY_2].around[EAST] = EMPTY_ROOM_2;
r[HALLWAY_2].around[SOUTH] = NO_ROOM;
r[HALLWAY_2].around[WEST] = NO_ROOM;

strcpy(r[EMPTY_ROOM_2].name, "Empty Room");
strcpy(r[EMPTY_ROOM_2].desc , "An empty room.");
r[EMPTY_ROOM_2].around[NORTH] = NO_ROOM;
r[EMPTY_ROOM_2].around[EAST] = NO_ROOM;
r[EMPTY_ROOM_2].around[SOUTH] = NO_ROOM;
r[EMPTY_ROOM_2].around[WEST] = HALLWAY_2;

strcpy(r[EXIT].name, "Exit");
strcpy(r[EXIT].desc, "You win lol");
r[EXIT].around[NORTH] = NO_ROOM;
r[EXIT].around[EAST] = NO_ROOM;
r[EXIT].around[SOUTH] = HALLWAY_2;
r[EXIT].around[WEST] = NO_ROOM;

}

// fills the array i with info on each item.
void item_setup(Item *i){
strcpy(i[APPLE].name, "Apple");
strcpy(i[APPLE].desc, "A bright red apple.");

strcpy(i[KEY].name, "Key");
strcpy(i[NO_ITEM].name, "A silver key.");

strcpy(i[NO_ITEM].name, "");
strcpy(i[NO_ITEM].desc, "");
}


As a simple test, I made currentRoom increment during the while loop, and had this output:

-- --


>
-- --


>
-- Hallway --
A long hallway.

>
-- Hallway --
A long hallway.

>
-- Troll's Domain --
You see a Troll.

>
-- Empty Room --
An empty room. There was no reason to come here.

>
-- Empty Room --
An empty room.

>
-- Exit --
You win lol


NO_ROOM and KITCHEN haven't had their info copied to the struct it seems. Can anyone help me work out where I'm going wrong?

Answer

Insufficient buffer size - off by 1.

// Room rooms[NO_ROOM];
Room rooms[NO_ROOM + 1];

or better

typedef enum {
  KITCHEN,
  PANTRY,
   ...
  NO_ROOM,

  // Insure ROOM_N is 1 greater than all the others.  
  // Putting it last usually does this.
  ROOM_N  
} en_rooms;

Room rooms[ROOM_N];

Same with Item items[NO_ITEM];

Likely other issues.

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