Sigsegv in malloc - c

Question

I want to save a struct containing a pointer that I use as a dynamic array but when I load the struct and malloc this pointer, it fails.
I have three structs (Orientation, ShipType, Status and PlayerType are enumerations, you can replace them by Int) :
struct Map
{
int width, height;
int* cases;
};
typedef struct Map Map;
struct Ship
{
int x, y, length, firstShoot, color;
int hasBeenDiscovered;
Orientation orientation;
ShipType type;
Status status;
};
typedef struct Ship Ship;
struct Player
{
int activeShips;
Map map[2];
char lastMoves[5][128];
Ship ships[10];
PlayerType type;
int shipcolor[4];
int color;
};
typedef struct Player Player;
I declare an array of 2 Player like this : Player players[2]; and initialize their properties. Then I want to save the struct in a file in order to load it afterwards.
Also, I use the Map struct as a 2d dynamic array using four functions :
void mallocMap(Map* map, int width, int height)
{
map->cases = malloc(sizeof(int) * width * height);
map->width = width;
map->height = height;
if (map->cases == NULL)
{
printf("Erreur d'allocation de memoire\n");
exit(0);
}
}
void freeMap(Map* map)
{
free(map->cases);
}
int getMapValue(Map map, int x, int y)
{
return *(map.cases + y*map.width + x);
}
void setMapValue(Map* map, int value, int x, int y)
{
*(map->cases + y*map->width + x) = value;
}
So when I store the struct, map.cases is only a pointer and I need to store the values at its address separately like so :
int save(Player players[2])
{
int* i;
FILE* file = NULL;
file = fopen("save.txt","w+");
if (file != NULL)
{
fwrite(players, sizeof(Player), 2, file);
fwrite(players[0].map[0].cases, sizeof(int), players[0].map[0].width * players[0].map[0].height, file);
fwrite(players[0].map[1].cases, sizeof(int), players[0].map[1].width * players[0].map[1].height, file);
fwrite(players[1].map[0].cases, sizeof(int), players[1].map[0].width * players[1].map[0].height, file);
fwrite(players[1].map[1].cases, sizeof(int), players[1].map[1].width * players[1].map[1].height, file);
}
else
{
// error
}
fclose(file);
return 1;
}
Each player has 2 maps so there are 4 maps to store at the end.
The problem is in my load() function :
int load(Player players[2])
{
FILE* file = NULL;
file = fopen("save.txt","r");
if (file != NULL)
{
int *i;
fread(players, sizeof(Player), 2, file);
mallocMap(&players[0].map[0], players[0].map[0].width, players[0].map[0].height);
mallocMap(&players[0].map[1], players[0].map[1].width, players[0].map[1].height);
mallocMap(&players[1].map[0], players[1].map[0].width, players[1].map[0].height);
mallocMap(&players[1].map[1], players[1].map[1].width, players[1].map[1].height);
fread(players[0].map[0].cases, sizeof(int), players[0].map[0].width * players[0].map[0].height, file);
fread(players[0].map[1].cases, sizeof(int), players[0].map[1].width * players[0].map[1].height, file);
fread(players[1].map[0].cases, sizeof(int), players[1].map[0].width * players[1].map[0].height, file);
fread(players[1].map[1].cases, sizeof(int), players[1].map[1].width * players[1].map[1].height, file);
}
else
{
// error
}
fclose(file);
return 1;
}
When I call mapAlloc(), it fails to allocate the memory and exit(0); my program stops.

Answer 1

The way you've declared your load function doesn't look right:
int load(Player* players[2])
This takes an array of pointers to Player, while your save routine takes an array of Player (i.e. Player players[2]). You probably need to change it to:
int load(Player players[2])
You're also reading the values back in to the wrong address:
for(i = players[0]->map[0].cases; i < players[0]->map[0].cases + players[0]->map[0].width * players[0]->map[0].height; i++)
fread(&i, sizeof(int), 1, file);
You're passing to fread the address of i. That means you're reading in an int and storing it in i, which is a local int * and not the dynamically allocated array you want to write to.
Remove the address-of operator here and pass in i directly, just like you do when you use fwrite
fread(i, sizeof(int), 1, file);
This will write the int that you read in into your array.
Also, there is no need to use loops to read / write individual ints here. Just do a single read / write passing in the number of values to read/write.
So saving would be:
fwrite(players[0].map[0].cases, sizeof(int), players[0].map[0].width * players[0].map[0].height, file);
fwrite(players[0].map[1].cases, sizeof(int), players[0].map[1].width * players[0].map[1].height, file);
fwrite(players[1].map[0].cases, sizeof(int), players[1].map[0].width * players[1].map[0].height, file);
fwrite(players[1].map[1].cases, sizeof(int), players[1].map[1].width * players[1].map[1].height, file);
And loading would be:
fread(players[0].map[0].cases, sizeof(int), players[0].map[0].width * players[0].map[0].height, file);
fread(players[0].map[1].cases, sizeof(int), players[0].map[1].width * players[0].map[1].height, file);
fread(players[1].map[0].cases, sizeof(int), players[1].map[0].width * players[1].map[0].height, file);
fread(players[1].map[1].cases, sizeof(int), players[1].map[1].width * players[1].map[1].height, file);
When compiling your code, there shouldn't be any warnings. If there are any, you're probably doing something wrong that you need to fix.