stackdump error?!!? 1

[NatMinx]

21 [main] calquery 6044 _cygtls:: handle_exception: Error while dumping state (probably corrupted stack)"
inside that stackdump file, it says "Error:STATUS_ACCESS_VIOLATION"

does anyone know what this means?! :'-(

my code worked like a charm 10 mins ago, I took a break, came back & ran it again (without making any changes) & thats the error I'm getting now!

 

[cpjust]

Where did that message come from? From the compiler, from running the program...?
What OS and compiler are you using?

 

[NatMinx]

typedef struct event_t {
char *event;
char *day;
char *year;
char *location;
} Event;

struct CalendarNode {
Event e;
struct CalendarNode *next;
};

int main (int argc, char **argv) {
.....
struct CalendarNode *list;
Event eee;
.....

add(list, eee);
.....
}

void add(struct CalendarNode *cal, Event someEvent) {
if(cal == NULL) {
cal = (struct CalendarNode *)malloc(sizeof(*cal));
cal->e = someEvent;
cal->next = NULL;

} else {
struct CalendarNode *p = cal;
while(p->next != NULL) {
p = p->next; ----> segfault from here after the last iteration

}
struct CalendarNode *q = (struct CalendarNode *)malloc(sizeof(*cal));
p->next = q;
q->e = someEvent;
q->next = NULL;
}
}

Its coming from cygwin (yes I have windows XP, dont look at me like that! )
Now I'm trying it on my skool's linux machine, still getting the segfault...

 

[cpjust]

I'm not sure if this is causing your current crash, but it certainly would crash if you pass NULL:

cal = (struct CalendarNode *)malloc(sizeof([COLOR=red]*cal[/color]));

If cal == NULL, you're de-referencing NULL here and BOOM!

BTW, use [ignore]

[/ignore] tags around your code... (Click the "Process TGML" link above the Submit Post button to see all the tags you can use)

Also, you shouldn't be casting malloc(). Here's why:

http://faq.cprogramming.com/cgi-bin/smartfaq.cgi?answer=1047673478&id=1043284351

Here are some more useful C/C++ FAQs:

http://faq.cprogramming.com/cgi-bin/smartfaq.cgi

 

[NatMinx]

but how would i fix the NULL case though?

 

[cpjust]

sizeof( CalendarNode )

instead of

sizeof( *cal )

 

[NatMinx]

Thanx a bunch big life saver!

 

[NatMinx]

I'm getting the segfault again :-(

what is wrong with this:::

typedef struct event_t {
        char *event;
        char *day;
        char *year;
        char *location;
} Event;

struct CalendarNode {
        Event e;
        struct CalendarNode *next;
};

int main (int argc, char **argv) {
    .....
    struct CalendarNode *list;
    Event eee;
    .....

    add(list, eee);
    .....
}

void add(struct CalendarNode *cal, Event someEvent) {
    struct CalendarNode *temp;
    temp = cal;

    if(cal == NULL) {
        cal = malloc(sizeof(*cal));
        cal->e = someEvent;
        cal->next = NULL;

    } else {
        while(temp->next != NULL) {
            temp = temp->next;   ----> segfault from here after the last iteration

        }
        temp->next = malloc(sizeof(*cal));
        temp = temp->next;
        temp->e = someEvent; 
        temp->next = NULL;
    }
}

 

[NatMinx]

Ahhh ignore the first post... that was the wrong version!

typedef struct event_t {
        char *event;
        char *day;
        char *year;
        char *location;
} Event;

struct CalendarNode {
        Event e;
        struct CalendarNode *next;
};

int main (int argc, char **argv) {
    .....
    struct CalendarNode **list; --> should this be initialised to null?
    Event eee;
    .....

    add(list, eee);
    .....
}

void add(struct CalendarNode **cal, Event someEvent) {
    !!!!segfault from here!!!!
    struct CalendarNode *temp;
    temp = *cal;

    if(*cal == NULL) {
        cal = malloc(sizeof(struct CalendarNode));
        temp = *cal;

    } else {
        while(temp->next != NULL) {
            temp = temp->next;
        }
        temp->next = malloc(sizeof(struct CalendarNode));
        temp = temp->next;
    }

    temp->e = someEvent; 
    temp->next = NULL;
}

 

[cpjust]

should this be initialised to null?

Yes, all pointers should be initialized to NULL if they aren't initialized to something valid.

I don't think you need to create a CalendarNode **list in main(). A single pointer should suffice: CalendarNode *list
Then when you pass it to add() pass the address of list with the & operator:

add( &list, eee );

temp = *cal;

Here you're dereferencing cal before checking if it's NULL, which is probably where it's going BOOM.