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Question

I have this program that is basically a mini game played in the terminal where the player is in a dungeon and tries to kill a dragon. I have a function that tries to save the game when the player chooses too and i see that its not writing the correct input, thus causing the load of that saved file to crash with a segmentation fault. I used hexdump to see that indeed the input I want to save isn’t correct (I have a saved file that has been given to me with the correct contents for a specific game). The following is my save_game function and relevant structs to the game. Can someone help me identify the issue?

int save_game(const graph_t *graph, const player_t *player) 
{
    // Create the file's name which is basically the player's name with a ".sav" extension to it
    char filename[NAME_SIZE];
    snprintf(filename, sizeof(filename), "%s.sav", player->name);

    // I open the file to write on it after creating it, or if it already exists I overwrite it
    int fd = open(filename, O_WRONLY | O_CREAT | O_TRUNC, 0644);
    if (fd == -1) return -1;

    /* Write the magic number which is a specific saved number that i write in the beggining and end of the file to identify them */

    if(write(fd, MAGIC_NUMBER, sizeof(MAGIC_NUMBER) - 1) != sizeof(MAGIC_NUMBER)-1) // χωρίς το null terminator
    {
        close(fd);
        return -1;
    }


    // Write player's details
    if (write(fd, &player->arrows, sizeof(player->arrows)) != sizeof(player->arrows) ||
        write(fd, &player->room->id, sizeof(player->room->id)) != sizeof(player->room->id)) 
    {
        close(fd);
        return -1;
    }

    // Write graph's details (The graph is basically the dungeon)
    if (write(fd, &graph->max_id, sizeof(graph->max_id)) != sizeof(graph->max_id) ||
        write(fd, &graph->num_vertices, sizeof(graph->num_vertices)) != sizeof(graph->num_vertices)) 
    {
        close(fd);
        return -1;
    }

    // Write every vertice's details (each vertex has an edge that leads to other vertices)
    for (unsigned int i = 0; i < graph->num_vertices; i++) 
    {
        vertex_t *vertex = graph->vertices[i];
        if (write(fd, &vertex->id, sizeof(vertex->id)) != sizeof(vertex->id) ||
            write(fd, &vertex->contents, sizeof(vertex->contents)) != sizeof(vertex->contents)) {
            close(fd);
            return -1;
        }
        unsigned int count = 0;
        for (edge_t *edge = vertex->edges; edge != NULL; edge = edge->next) 
        {
            count++;
        }

        if (write(fd, &count, sizeof(count)) != sizeof(count)) 
        {
            close(fd);
            return -1;
        }
        for (edge_t *edge = vertex->edges; edge != NULL; edge = edge->next) 
        {
            if (write(fd, &edge->to->id, sizeof(edge->to->id)) != sizeof(edge->to->id)) 
            {
                close(fd);
                return -1;
            }
        }
    }

    // Write the magic number again at the end of the file
    if (write(fd, MAGIC_NUMBER, sizeof(MAGIC_NUMBER) - 1) != sizeof(MAGIC_NUMBER) - 1) {
        close(fd);
        return -1;
    }
    close(fd);
    return 0;
}

typedef struct {
    char name[NAME_SIZE];
    unsigned int arrows;
    vertex_t *room;
} player_t;

typedef struct  _vertex {
    unsigned int id; // unique id
    contents_t contents;
    struct _edge *edges; // a vertex connects to a list of edges
} vertex_t;

typedef struct _edge {
    vertex_t *to;  // the other adjacent vertex
    struct _edge *next;
} edge_t;
    
typedef struct {
    unsigned int max_id; // maximum vertex id given at any time
    unsigned int num_vertices;
    vertex_t **vertices;  // the graph is a dynamic array of pointers to vertices
} graph_t;

the following is the output i got from the hexdump after I compared the file’s content i got with the desired content of the saved file. Note that “Dr460N5D3N” is the magic number. The first is the file i created and the second one is the desired output.

2,23c2,24
< 00000010  00 00 0c 00 00 00 0d 00  00 00 01 00 00 00 00 00  |................|
< 00000020  00 00 03 00 00 00 0a 00  00 00 0b 00 00 00 0c 00  |................|
< 00000030  00 00 02 00 00 00 02 00  00 00 04 00 00 00 0d 00  |................|
< 00000040  00 00 08 00 00 00 09 00  00 00 0c 00 00 00 03 00  |................|
< 00000050  00 00 00 00 00 00 03 00  00 00 0b 00 00 00 07 00  |................|
< 00000060  00 00 0c 00 00 00 04 00  00 00 00 00 00 00 03 00  |................|
< 00000070  00 00 06 00 00 00 07 00  00 00 09 00 00 00 05 00  |................|
< 00000080  00 00 02 00 00 00 03 00  00 00 06 00 00 00 07 00  |................|
< 00000090  00 00 09 00 00 00 06 00  00 00 01 00 00 00 03 00  |................|
< 000000a0  00 00 0a 00 00 00 05 00  00 00 04 00 00 00 07 00  |................|
< 000000b0  00 00 04 00 00 00 03 00  00 00 03 00 00 00 05 00  |................|
< 000000c0  00 00 04 00 00 00 08 00  00 00 00 00 00 00 03 00  |................|
< 000000d0  00 00 0b 00 00 00 0a 00  00 00 02 00 00 00 09 00  |................|
< 000000e0  00 00 03 00 00 00 04 00  00 00 0d 00 00 00 05 00  |................|
< 000000f0  00 00 04 00 00 00 02 00  00 00 0a 00 00 00 01 00  |................|
< 00000100  00 00 03 00 00 00 08 00  00 00 06 00 00 00 01 00  |................|
< 00000110  00 00 0b 00 00 00 00 00  00 00 03 00 00 00 03 00  |................|
< 00000120  00 00 08 00 00 00 01 00  00 00 0c 00 00 00 01 00  |................|
< 00000130  00 00 03 00 00 00 03 00  00 00 02 00 00 00 01 00  |................|
< 00000140  00 00 0d 00 00 00 00 00  00 00 02 00 00 00 09 00  |................|
< 00000150  00 00 02 00 00 00 44 72  34 36 30 4e 35 44 33 4e  |......Dr460N5D3N|
< 00000160
---
> 00000010  00 00 0d 00 00 00 0d 00  00 00 44 72 34 36 30 4e  |..........Dr460N|
> 00000020  35 44 33 4e 01 00 00 00  00 00 00 00 02 00 00 00  |5D3N............|
> 00000030  02 00 00 00 03 00 00 00  00 00 00 00 04 00 00 00  |................|
> 00000040  00 00 00 00 05 00 00 00  02 00 00 00 06 00 00 00  |................|
> 00000050  01 00 00 00 07 00 00 00  04 00 00 00 08 00 00 00  |................|
> 00000060  00 00 00 00 09 00 00 00  03 00 00 00 0a 00 00 00  |................|
> 00000070  01 00 00 00 0b 00 00 00  00 00 00 00 0c 00 00 00  |................|
> 00000080  01 00 00 00 0d 00 00 00  00 00 00 00 03 00 00 00  |................|
> 00000090  0a 00 00 00 0b 00 00 00  0c 00 00 00 04 00 00 00  |................|
> 000000a0  0d 00 00 00 08 00 00 00  09 00 00 00 0c 00 00 00  |................|
> 000000b0  03 00 00 00 0b 00 00 00  07 00 00 00 0c 00 00 00  |................|
> 000000c0  03 00 00 00 06 00 00 00  07 00 00 00 09 00 00 00  |................|
> *
> 000000e0  03 00 00 00 0a 00 00 00  05 00 00 00 04 00 00 00  |................|
> 000000f0  03 00 00 00 03 00 00 00  05 00 00 00 04 00 00 00  |................|
> 00000100  03 00 00 00 0b 00 00 00  0a 00 00 00 02 00 00 00  |................|
> 00000110  04 00 00 00 0d 00 00 00  05 00 00 00 04 00 00 00  |................|
> 00000120  02 00 00 00 03 00 00 00  08 00 00 00 06 00 00 00  |................|
> 00000130  01 00 00 00 03 00 00 00  03 00 00 00 08 00 00 00  |................|
> 00000140  01 00 00 00 03 00 00 00  03 00 00 00 02 00 00 00  |................|
> 00000150  01 00 00 00 02 00 00 00  09 00 00 00 02 00 00 00  |................|
> 00000160  44 72 34 36 30 4e 35 44  33 4e                    |Dr460N5D3N|
> 0000016a

I tried hexdump and some lldb but i couldnt really pinpoint the issue. The sanitizer also didnt crash when saving.

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