在信号处理器函数中执行非本地跳转

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65

#define _GNU_SOURCE // 添加该定义以正常使用strsignal()、sigaction()
#include <string.h>
#include <setjmp.h>
#include <signal.h>
#include "signal_functions.h"
#include "tlpi_hdr.h"

static volatile sig_atomic_t canJump = 0;

#ifdef USE_SIGSETJMP
static sigjmp_buf senv;
#else
static jmp_buf env;
#endif

static void handler(int sig) {
    printf("Received signal %d (%s), signal mask is:\n", sig, strsignal(sig));
    printSigMask(stdout, NULL);

    if (!canJump) { // 若canJump为0
        printf("'env' buffer not yet set, doing a simple return\n");
        return;
    }

#ifdef USE_SIGSETJMP
    siglongjmp(senv, 1);
#else
    longjmp(env, 1);
#endif
}

int main(int argc, char *argv[]) {
    struct sigaction sa;
    printSigMask(stdout, "Signal mask at startup:\n");  // 打印最开始的信号掩码
    sigemptyset(&sa.sa_mask);
    sa.sa_flags = 0;
    sa.sa_handler = handler;
    if (sigaction (SIGINT, &sa, NULL) == -1)
        errExit("sigaction");
#ifdef USE_SIGSETJMP
    printf("Calling sigsetjmp()\n");
    /*
        
    */
    if (sigsetjmp(senv, 1) == 0)
#else
    printf("Calling setjmp()\n");
    // 设置跳转目标，并初始化env
    if (setjmp(env) == 0)
#endif
        // 当从处理器函数直接返回之后才会执行该语句
        canJump = 1;
    else 
        // 当从处理器函数执行非本地跳转之后才会执行该语句
        printSigMask(stdout, "After jump from handler, signal mask is:\n");
    
    printf("Will be paused\n");
    for (;;)
        /*
            等待信号，
            若接收到SIGINT，则跳转到处理器函数中，再由longjmp()/siglongjmp()跳转到setjmp()/sigsetjmp()
            具体是哪个跳转函数，则取决于是否宏定义了USE_SIGSETJMP
        */
        pause();
}