strtok(), strdup() error

I don't really know how to even begin solving this problem. Basically, I have a structure:

Code:

---

struct Items{
char*desc;
char*name;
char*behave;
struct Areas*loc;
struct Items*next;
struct Items*prev;
USE_FUNCTION use;
};

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I want to fill out the fields of the structure...

Code:

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fgets (input, 255, file); if ((p = strchr(input, '\n')) != NULL) *p = '\0';
                        new=createitem("NULL", "NULL", currentarea);
                        name=strtok(input,",");
                        desc=strtok(NULL, ",");
                        behavior=strtok(NULL, ",");
                        new->name=strdup(name);
                        new->desc=strdup(desc);
                        new->behave=strdup(behavior);
                        new->loc=&a[currentarea]; printf("%s", new->name);
                        new->prev=NULL; new->next=NULL; printf("%s", new->name);

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The problem here is that when I assigned new->prev and new->next to NULL, the value of new->name changes! Apparently it is resetting the value to NULL. I'm not sure why at all, but it is causing segmentation faults.

I changed the code slightly:

Code:

---

new->loc=&a[currentarea]; printf("%s", new->name);
                        new->prev=NULL; printf("%s", new->name);
                        new->next=NULL; printf("%s", new->name);

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If the name is "paperweight", then it will print "paperweightpape" rather than the expected "paperweightpaperweightpaperweight"

This is the createitem() function:

Code:

---

Items*createitem(char*name, char*desc, int currentarea){

Items*new=(Items*)malloc(sizeof(Items*));
new->next=NULL;
new->prev=NULL;
new->behave=NULL;
new->desc=NULL;
printf("\nCreated: %p", new);
return(new);

}

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I might have just fixed it by changing this line: [Items*new=(Items*)malloc(sizeof(Items*));} to

Code:

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Items*new=(Items*)malloc(sizeof(Items));

---

Could someone explain how exactly my code is affected by setting the malloc size to the size of a pointer. Obviously its the incorrect size, I just wonder what is happening.

There are more problems than you appear to realize...

First... if you are using fgets to load a line from the file, the companion function would be sscanf() to burst out your data. strtok() is destructive.

Second rather than using strdup() you should create actual char array[] space in your struct...

Code:

---

struct Items{
char desc[64];
char name[32];
char behave[16];
struct Areas*loc;
struct Items*next;
struct Items*prev;
USE_FUNCTION use;
};

---

Then you can use sscanf() to load the struct directly...

Code:

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fgets(input, 255, file)
sscanf(%s,%s,%s", items.desc, items.name, items.behave)

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Believe me, it's going to work a lot better than what you have.

Quote:

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Originally Posted by Adam Rinkleff

I might have just fixed it by changing this line: [Items*new=(Items*)malloc(sizeof(Items*));} to

Code:

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Items*new=(Items*)malloc(sizeof(Items));

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Could someone explain how exactly my code is affected by setting the malloc size to the size of a pointer. Obviously its the incorrect size, I just wonder what is happening.

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So if you allocate four bytes for an object, and then try to write 437 bytes to that object, where are the other 433 bytes going to go? (Hint: on top of other things, is where.)