CODEWITHSUNDEEP
clinked-listsegmentation-faultmalloc
tjb1982
tjb1982

Reputation: 2259

Segmentation fault with malloc on char* in struct

I'm teaching myself C and for fun I thought it would be cool to write a small web framework. The code I'm working on at the moment is for registering routes/handlers.

I've run into a segmentation fault with malloc, but strangely only on the fourth time it is called. I've marked the point in the code where the segmentation fault occurs. I'm not sure how to debug it other than wrapping areas of the code with printfs and putss. I've tried using valgrind to debug this, but the segmentation fault doesn't actually happen when I run valgrind. Valgrind does tell me that there is a memory leak stemming from the same malloc, though. So obviously I'm doing something wrong there, but I don't know what.

FYI, destroy_routes is called just before the child process is terminated.

struct route {
    char *path;
    enum method method;
    int(*handler)(struct request *, int sock);
    struct route *next;
};


static struct route *routes;

void
register_route(char *path, enum method method,
               int(*handler)(struct request *, int))
{
    struct route *route;

    if (routes == NULL)
        routes = route = malloc(sizeof(struct route));
    else {
        route = routes;
        while (route->next)
            route = route->next;

        route->next = malloc(sizeof(struct route));
        route = route->next;
    }

    route->path = malloc((strlen(path) + 1) * sizeof(char)); /* <== HERE is where the segmentation fault occurs only on the fourth time */
    strcpy(route->path, path);

    route->method = method;
    route->handler = handler;

    printf("route created: %s, %i, %p\n", route->path, route->method, (void *)route->handler);
}

void
destroy_routes()
{
    struct route *prev;
    int i = 0;
    while (routes) {
        free(routes->path);
        prev = routes;
        routes = routes->next;
        free(prev);
        i++;
    }
    printf("destroyed %i routes\n", i);
}

void
register_routes()
{
    register_route("/post", GET, &do_something);
    register_route("/post", POST, &do_something_else);
    register_route("/post/:id", GET, &do_something);
    register_route("/post/:id/children", POST, &do_something_else);
}

Upvotes: 0

Views: 349

Answers (1)

user1969104
user1969104

Reputation: 2420

You missed to set the next pointer to NULL. That could be the issue.

route->method = method;
route->handler = handler;
route->next = NULL;

Upvotes: 5

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