Malloc结构 分段故障

Question

So I defined my struct outside of any function:

typedef struct limb{
    char c;
    struct limb *child;
    int x;
    int y;
}limb;

And tried to allocate memory to it:

limb *body;
body = malloc(sizeof(limb));
body->child = malloc(sizeof(limb));

But it gives me segmentation fault. Any help will be appreciated.

gdb:

Program received signal SIGSEGV, Segmentation fault.
0x0000000000409162 in wsyncdown ()
(gdb) x 0x0000000000409162
0x409162 <wsyncdown+18>:    0x406f8b48

Whole code (hope it helps):

#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <ncurses.h>

int max_x, max_y;

void welcome_screen();
void terrain();

typedef struct limb{
    char c;
    struct limb *child;
    int x;
    int y;
}limb;

int main()
{
    welcome_screen();
    terrain();
    return 0;
}
void terrain()
{
    WINDOW *terrain;
    int startx, starty, width, height;
    keypad(stdscr, TRUE);
    wrefresh(terrain);
    height = 60;
    width = 100;
    starty = (LINES - height) / 2;
    startx = (COLS - width) / 2;
    terrain = newwin(height, width, starty, startx);
    wborder(terrain, '|', '|', '-', '-', '+', '+', '+', '+');
    wrefresh(terrain);
    limb *body;
    if(!(body = malloc(sizeof(limb)))){
        printw("SEGMENTATION FAULT");
        getch();
    }
    /*body->child = malloc(sizeof(limb));*/


    while(1);
    endwin();
}

Answer 1

This causes undefined behaviour:

WINDOW *terrain;
// ...
wrefresh(terrain);

because you use an uninitialized variable. Take out the wrefresh(terrain) line. To avoid this sort of error you could delay declaring variables until you are ready to initialize them:

// ...
WINDOW *terrain = newwin(height, width, starty, startx);