dynamic allocation in code blocks

Question

I am trying to make a linked list in C. I've got the program up and running in Turbo C++ which we use at school. When I try putting my code in Code Blocks I cannot get it running. I stripped a big part of the code so you can see the part that stops working when I debug. When it compiles it says nothing about an error but simply stops working. I am thinking it might me because of how I dynamically allocate memory.

#include <stdio.h>
#include <stdlib.h>

struct data
{
    int a;
    int b;
};

struct node
{
    struct data info;
    struct node *urm;
};

struct lista
{
    int lungime;
    struct node *curent, *prim, *ultim;
};

struct lista *listax;

int creare(struct lista *LP)
{
    LP->prim = (struct node*)malloc(sizeof(struct node));
    LP->ultim = (struct node*)malloc(sizeof(struct node));
    LP->prim->urm = LP->ultim;
    LP->ultim->urm = NULL;
    LP->curent=LP->prim;
    LP->lungime = 0;
    return 1;
}

int main()
{
    creare(listax);
    return 0;
}

I have to use this type of declaration because this how our teacher wants us to present the list (with a start and end node). Any help is appreciated.

*edit:
prim is first
ultim is last
lungime is length
urm is next

Indent your code. Add blank lines to separate into segments with close semantic meaning. What you present is horrible to read as a human. Code is about communicating with other programmers (i.e other people that don't share your mind), not just machines. — StoryTeller - Unslander Monica, Apr 09 '17 at 10:39
@BorisBolshem `listax` is initialized to `NULL` because it is a file scope variable. — BLUEPIXY, Apr 09 '17 at 11:42
Would somebody like to create an answer? I like Q/A pairs so much better than Q/comment pairs. — Yunnosch, Apr 09 '17 at 17:40
Well your program doesn't attempt to output anything, so even after you fix the allocation error it woud still just stop working, exactly as it does now. — n. m. could be an AI, Apr 10 '17 at 11:03

score 1 · Accepted Answer · edited May 23 '17 at 12:02

Your memory allocation is indeed incorrect. Before attempting to assign to each of the members of LP you must assign space for the struct pointed to by LP itself, for example:

LP = malloc(sizeof(*LP));

Additional advice

When you allocate space you should normally check the result of the allocation function (malloc()/calloc()/realloc()) as the function may return null if it was not able to assign the memory requested. You can do this with a simple if statement after the malloc(), such as: if (!LP) return -1;
Do not cast the return value of malloc() .
It's usually better to use sizeof on a variable name rather than a type, eg LP->prim = malloc(sizeof(LP->prim));
Anytime you allocate memory you should remember to free the allocated memory when finished with it! Use free() to do this. If you do not free memory a program leaks memory, that is it keeps allocating more and more each time and eventually all of the memory on your computer is allocated, even though your program only actually needs to use a little bit of what it has allocated. See this and this.
As pointed out by @StoryTeller, use white space to make your code readable - having it all bunched up together in some effort to make it appear shorter, or something, does not make it look professional, it just looks unreadable (and thus hard for other people to help you with it).

Using white space to divide words or group information may not be the norm in some writing systems (some middle eastern languages place less or no importance on it for example), but a lot of code is written in American English, which does. As such, writing professional code that co-workers, teachers or contributors can easily read will involve using white space in this manner and will be something you need to learn, just the same learning a language's syntax.

This question may be a good point to start with code style, but you can also check out some of the named C style guides, such as GNU, Linux Kernel, BSD, etc

Thanks a lot for your help everyone.I managed to make it work.I found it weird that with the same code I managed to get it working in Turbo c++ but the code blocks editor won't do the same.But now I do understand that I need to assign space for the struct pointed to by LP. — Mihai Adrian, Apr 10 '17 at 15:51
You're welcome @MihaiAdrian. I have to admit that I know very little about Turbo C, but what I do know is that it is somewhat different to standard C (so the code from one is not necessarily valid in the other). — Toby, Apr 10 '17 at 15:54

dynamic allocation in code blocks

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