Error Jmp

int setjmp(jmp_buf env);
int sigsetjmp(sigjmp_buf env, int savesigs);

void longjmp(jmp_buf env, int val);
void siglongjmp(sigjmp_buf env, int val);

/usr/include/setjmp.h

#include <bits/setjmp.h>        /* Get '__jmp_buf'.  */
#include <bits/types/__sigset_t.h>
 
/* Calling environment, plus possibly a saved signal mask.  */
struct __jmp_buf_tag
{
    /* NOTE: The machine-dependent definitions of `__sigsetjmp'
       assume that a `jmp_buf' begins with a `__jmp_buf' and that
       `__mask_was_saved' follows it.  Do not move these members
       or add others before it.  */
    __jmp_buf __jmpbuf;     /* Calling environment.  */
    int __mask_was_saved;   /* Saved the signal mask?  */
    __sigset_t __saved_mask;    /* Saved signal mask.  */
};

// 上面的结构体成员,分别是调用环境(保存堆栈指针, 指令等), 是否保存标志位的标志, 保存的信号掩码
// 而且,注释严重声明: 前两个成员是不能互相交换位置的.
// 如果要详细查看__jmp_buf 可以去看/usr/include/bits/setjmp.h

//main.c
#include <stdio.h>
#include <stdlib.h>
#include <setjmp.h>
#include "set.h"
int main(void)
{
    int ret_val;

    if (ret_val = setjmp(jmp)) {
        printf("Back to main.c and ret_val is %d\n", ret_val);
    } else {
        printf("First time through\n");
        printf("The ret_val: %d\n", ret_val);
        test();
    }

    return 0;
}

// set.h
#ifndef _SET_H
#define _SET_H          
#include <setjmp.h> 
jmp_buf jmp;     
void test(void);
#endif

// set.c
#include <stdio.h>
#include <stdlib.h>
#include <setjmp.h>            
#include "set.h"               
     
void test(void)                
{    
    printf("This is set.c\n"); 
    longjmp(jmp, 4);           
    printf("YOu can't get here!\n");
}

if (error1) {
	do_something();
} else {
	do_something();
}
if (error2) {
	do_something();
} else {
	do_something();
}

do_something();
if (error1)
	goto error;
if (error2)
	goto error;
	
error:
	do_something();