如何修复由于递归算法造成的Segfault

Question

我试图编写一个完美的迷宫生成器，但是由于递归导致Segfault，当迷宫太大时，代码中的问题很少。这里是代码的主要部分：

t_maze  *init_maze(int w, int h) 
{ 
    t_maze *maze; 
    int  j; 
    int  i; 

    if ((maze = malloc(sizeof(t_maze))) == NULL) 
    return (NULL); 

    maze->w = w; 
    maze->h = h; 

    if ((maze->cells = malloc(sizeof(char *) * maze->h)) == NULL) 
    return (NULL); 

    j = -1; 
    while (++j < maze->h) 
    { 
    if ((maze->cells[j] = malloc(sizeof(char) * maze->w)) == NULL) 
     return (NULL); 

    i = -1; 
    while (++i < maze->w) 
     maze->cells[j][i] = (j % 2 == 1 || i % 2 == 1) ? (1) : (0); 
    } 
    return (maze); 
} 

void  detect_neighbours(t_maze *maze, char *neighbours, int x, 
       int y) 
{ 
    int  i; 

    // I fill the array with 1 (means there is no neighbours) 
    // If there is a neighours, I set the cell to 0 
    // In this order: Top, right, bottom, left 
    i = -1; 
    while (++i < 4) 
    neighbours[i] = 1; 
    if (y - 2 >= 0 && x >= 0 && y - 2 < maze->h 
     && x < maze->w && maze->cells[y - 2][x] == 0) 
    neighbours[0] = 0; 
    if (x + 2 >= 0 && x + 2 < maze->w && y >= 0 && y < maze->h 
     && maze->cells[y][x + 2] == 0) 
    neighbours[1] = 0; 
    if (y + 2 < maze->h && y + 2 >= 0 && x >= 0 
     && x < maze->w && maze->cells[y + 2][x] == 0) 
    neighbours[2] = 0; 
    if (x - 2 >= 0 && x - 2 < maze->w && y >= 0 && y < maze->h 
     && maze->cells[y][x - 2] == 0) 
    neighbours[3] = 0; 
} 

int  there_is_no_neighbours(char *neighbours) 
{ 
    int  i; 

    // this function returns 0 if there is at least 1 neigbours 
    i = -1; 
    while (++i < 4) 
    if (neighbours[i] == 0) 
     i = 41; 
    if (i == 42) 
    return (0); 
    return (1); 
} 

void  set_maze_protected(t_maze *maze, int y, int x, int val) 
{ 
    // To prevent segfault when I put values in the maze, 
    // I check the x and y keys 
    if (x >= 0 && y >= 0 && x < maze->w && y < maze->h) 
    maze->cells[y][x] = val; 
} 

int  build_maze(t_maze *maze, int x, int y) 
{ 
    char  neighbours[4]; 
    int  i; 
    int  ret; 

    ret = 0; 
    detect_neighbours(maze, neighbours, x, y); 
    if (there_is_no_neighbours(neighbours) == 1) 
    return (0); 
    i = rand() % 4; 
    while (neighbours[i] == 1) 
    i = rand() % 4; 
    if (i == 0) 
    { 
     set_maze_protected(maze, y - 1, x, 2); 
     set_maze_protected(maze, y - 2, x, 2); 
     ret = build_maze(maze, x, y - 2); 
    } 
    if (i == 1) 
    { 
     set_maze_protected(maze, y, x + 1, 2); 
     set_maze_protected(maze, y, x + 2, 2); 
     ret = build_maze(maze, x + 2, y); 
    } 
    if (i == 2) 
    { 
     set_maze_protected(maze, y + 1, x, 2); 
     set_maze_protected(maze, y + 2, x, 2); 
     ret = build_maze(maze, x, y + 2); 
    } 
    if (i == 3) 
    { 
     set_maze_protected(maze, y, x - 1, 2); 
     set_maze_protected(maze, y, x - 2, 2); 
     ret = build_maze(maze, x - 2, y); 
    } 
    while (ret != 0) 
    ret = build_maze(maze, x, y); 
    return (1); 
} 
int  main() 
{ 
    t_maze *maze; 
    int  w; 
    int  h; 

    w = 50; 
    h = 50; 
    srand(time(NULL) * getpid()); 
    if ((maze = init_maze(w, h)) == NULL) 
    return (1); 
    maze->cells[0][0] = 2; 
    build_maze(maze, 0, 0); 
    // display_maze shows values in the 2D array (maze->cells) 
    display_maze(maze); 
    return (0); 
} 

我调用这个函数中主要有以下调用：

build_maze(maze, 0, 0); 

功能检测是小区有邻居，如果有，则函数调用其中一人随机地打开两人之间的门。

如果x和y的参数大于2500，例如它会出现段错误。 （如果它小于2500，它会很好）

如何解决这个问题？

我了解尾部调用，但我忽略了如何实现，在这种情况下，

谢谢

问候

Answer 1

可以增加堆栈大小。

在POSIX系统上，您可以使用以下代码。

#include<stdio.h> 
#include <sys/resource.h> 
#define required_stack_size 0x8000000 // change this to the stack size you need 

int main (int argc, char **argv) 
{ 
    struct rlimit rl; 
    int result; 

    if((result = getrlimit(RLIMIT_STACK, &rl)) < 0) 
    { 
     fprintf(stderr, "getrlimit returned result %d\n", result); 
     return -1; 
    } 
    if(rl.rlim_cur<required_stack_size) 
    { 
     rl.rlim_cur = required_stack_size; 
     if((result = setrlimit(RLIMIT_STACK, &rl)) < 0) 
     { 
      fprintf(stderr, "setrlimit returned result = %d\n", result); 
      return -1; 
     } 
    } 

    //the rest code 
    return 0; 
}