memory error (access violation) on method parameters - c++

Question

I've got weird problem. I'm trying to write simple game in C++, but I failed on objects and data types. There's a code:
// C++
// Statki
#include <stdio.h>
#include <time.h>
#include <map>
#include <vector>
#include <string>
#include <list>
#define D true
using namespace std;
void _(char* message){printf("%s\n",message);};
struct relpoint { int x,y; };
struct point { int x,y; };
struct size { int w,h; };
map<const char*, vector<relpoint> > shipshape;
list<char*> shipTypes = {"XS", "S", "M", "L", "XL"};
string alpha="ABCDEFGHIJKLMNOPRSTUVWXYZ";
enum fieldtype { UNKNOWN=-1,EMPTY=0,SHIP=1,HIT=2,MISS=3,};
enum rotation { EAST=0, SOUTH=1, WEST=2, NORTH=3 };
class Ship
{
char* type;
};
class Sea
{
public:
void init(size mapsize) { init( mapsize, EMPTY ); };
void init(size mapsize, fieldtype fill)
{
if(D)printf("Generating sea\n");
vector<fieldtype> v;
seamap.reserve(mapsize.h);
v.reserve(mapsize.w);
for (int y=0; y<mapsize.h; y++)
{
v.clear();
for(int x=0; x<mapsize.w; x++)
{
v.push_back(fill);
}
seamap.push_back(v);
}
view();
};
bool place_ship(Ship ship);
void view()
{
for( vector< vector<fieldtype> >::const_iterator yy = seamap.begin(); yy != seamap.end(); ++yy )
{
for( vector<fieldtype>::const_iterator xx = (*yy).begin(); xx != (*yy).end(); ++xx )
{
if(D)printf("%d ", *xx);
}
if(D)printf("\n");
}
};
private:
vector< vector<fieldtype> > seamap;
};
class Game
{
public:
void initmap(size mapsize)
{
if(D) printf("\nInit %d×%d map\n", mapsize.w, mapsize.h);
(*enemymap).init(mapsize, UNKNOWN);
//(*selfmap).init(mapsize);
};
bool placeship(string type, point position, rotation rotate);
fieldtype shoot(point target);
void viewmap(){(*selfmap).view();};
bool eog();
Sea * enemymap;
Sea * selfmap;
};
class Bot
{
public:
void init(size mapsize)
{
if(D)_("Init Bot");
}
private:
Game * g;
};
class Player
{
public:
Player() { if(D){_("Player fake init");} };
void init(size mapsize)
{
(*g).initmap(mapsize);
};
void viewmap(){(*g).viewmap();};
private:
Game * g;
};
class Router
{
public:
void startgame();
void welcomescreen()
{
printf("\n\n\n\t\t\tShips minigame\n\t\t\t\tby Kris\n\n");
mainmenu();
};
void mainmenu()
{
printf("Menu (type letter):\n\tN: New game\n\tS: Settings\n\tQ: Quit game\n\n > ");
char opt;
opt = toupper(getchar());
size ms;
switch(opt)
{
case 'N':
ms = getmapsize();
(*P1).init(ms);
(*P2).init(ms);
break;
case 'S':
break;
case 'Q':
break;
default:
printf("Invalid option %c", opt);
mainmenu();
}
};
private:
Player * P1;
Bot * P2;
size getmapsize()
{
size ms;
printf("\nSet map size (X Y)\n > ");
scanf("%d %d", &ms.w, &ms.h);
return ms;
};
};
int main () {
vector<relpoint> shp;
shp.reserve(5);
list<char*>::const_iterator tp = shipTypes.begin();
shp.push_back({0,0});
shipshape[*(tp++)] = shp;
shp.push_back({1,0});
shipshape[*(tp++)] = shp;
shp.push_back({2,0});
shipshape[*(tp++)] = shp;
shp.push_back({3,0});
shipshape[*(tp++)] = shp;
shp.push_back({2,1});
shipshape[*tp] = shp;
Router R;
R.welcomescreen();
printf("\n\n");
return 0;
}
It can be compiled, but after line Init 5×5 map program stops with Naruszenie ochrony pamięci (Memory access violation in polish) error. Problem seems to occur at both Sea::init() functions.
I'm compiling it with g++ -std=c++0x -Wno-write-strings ships2.cpp (to prevent warnings) on Ubuntu.
Any idea what's wrong with it?

Answer 1

All the classes contain pointers, but you never seem to initialize the pointers or allocate space for the objects they should point to.
Doing this
(*enemymap).init(mapsize, UNKNOWN);
when enemymap doesn't point anywhere, is an almost sure way to get an access violation.

Answer 2

You are using an uninitialized pointer. You can fix it by instantiating an object here, or in a constructor somewhere else.
Here is an example of instantiating in the initmap call.
void initmap(size mapsize)
{
// Initialize the pointer by instantiating a class
enemymap = new Sea;
if(D) printf("\nInit %d×%d map\n", mapsize.w, mapsize.h);
(*enemymap).init(mapsize, UNKNOWN);
//(*selfmap).init(mapsize);
};

Answer 3

+1 for Bo. But for your own sake:
compile with -g and then then
gdb ./mygame.bin
type 'run'
after setting the map size 5 5 :
Program received signal SIGSEGV, Segmentation fault.
mainmenu (this=<optimized out>) at memacvio.cpp:158
158 (*P1).init(ms);
This should tell you that P1 is probably not a valid poiner.