}
static void dump_map(const char* fname)
{
    FILE* fp = fopen(fname, "w");
    if ( !fp )
        return;
    int min_x = GXM, max_x = 0, min_y = GYM, max_y = 0;
    for (int i = 0; i < GXM; i++)
        for (int j = 0; j < GYM; j++)
            if (env.map[i][j].known())
            {
                if ( i > max_x )
                    max_x = i;
                if ( i < min_x )
                    min_x = i;
                if ( j > max_y )
                    max_y = j;
                if ( j < min_y )
                    min_y = j;
            }
    
    for ( int y = min_y; y < max_y; ++y )
    {
        for ( int x = min_x; x < max_x; ++x )
            fputc( env.map[x][y].glyph(), fp );
        fputc('\n', fp);
    }
    fclose(fp);

    std::string map_file_name = file_name + ".map";
    dump_map(map_file_name.c_str());