C：使用参数声明函数会改变其行为...？

Question

我正在玩弄信号，叉子和execve，我写了一个玩具程序，它使用fork()来创建一个调用另一个玩具程序的子进程。然后，父母设置一个警报，在一定的秒数后终止该功能。

#include <stdio.h> 
#include <stdlib.h> 
#include <unistd.h> 
#include <ctype.h> 
#include <signal.h> 

pid_t childPid; 

pid_t Fork() 
{ 
    pid_t pid; 

    if ((pid = fork()) < 0) 
     printf("Error:\n"); 
    return pid; 
} 

void killhandler(int sig) 
/*This will be called when we receive a SIGALRM*/ 
{ 
    int status; 
    printf("\nAssassin: *ksh* Received order to kill process: %d\n", (int)childPid); 
    if (!(status = kill(childPid, SIGKILL))) { 
     printf("Assassin: Clean and discreet. My work here is done. *ksh*\n"); 
    } else { 
     printf("Assassin: He got away!\n"); 
    } 
} 

void forkyMcFork() 
{ 
    pid_t pid; 
    int status; 
    /*Generate information for new program*/ 
    char* argv[] = {"problem5", "Hello"}; 
    char* envp[] = {"PANTS=JEANS"}; 
    char* func = "problem5"; 

    /* Create child process, child process calls executable "problem5" */ 
    if ((pid = Fork()) == 0) { 
     printf("Child: I am a child! Woohoo!\n"); 
     if (execve(func, argv, envp) < 0) 
      printf("Child: error, %s not found\n", func); 
     while(1); 
    } 
    else { 
     /* Parent process sets alarm, then prints a message depending on exit status*/ 
     childPid = pid; 
     alarm(3); 
     printf("Parent: I am the parent!\n"); 
     waitpid(-1, &status, 0); 
     if (!WIFEXITED(status)) { 
      printf("Parent: Oh no, what happened to my baby!!!\n"); 
      exit(0); 
     } else { 
      printf("Parent: Child came home without any problems.\n"); 
     } 
    } 
} 

int main(int argc, char const *argv[]) 
{ 
    signal(SIGALRM, killhandler); 
    forkyMcFork(); 
    return 0; 
} 

这里的怪异的一部分：如果我声明功能forkyMcFork()为不接受参数，然后设置参数手动alarm()，然后它就像我希望：子进程开始problem5，其请求一些来自用户的输入，然后3秒，killhandler运行后，发现子进程，并杀死它：

$ ./forkfun 
Parent: I am the parent! 
Child: I am a child! Woohoo! 
Please type name. If finished press enter: Haha 
Please type name. If finished press enter: 
Assassin: *ksh* Received order to kill process: 42409 
Assassin: Clean and discreet. My work here is done. *ksh* 
Parent: Oh no, what happened to my baby!!! 
$ 

但是，如果我声明，而不是forkyMcFork(int secs)然后用alarm(secs)，应当由被称为外部程序找不到子项目中的语句。警报按预期运行，因此在几秒钟后，子进程将被削减。

这里的非工作代码：

#include <stdio.h> 
#include <stdlib.h> 
#include <unistd.h> 
#include <ctype.h> 
#include <signal.h> 

pid_t childPid; 

pid_t Fork() 
{ 
    pid_t pid; 

    if ((pid = fork()) < 0) 
     printf("Error:\n"); 
    return pid; 
} 

void killhandler(int sig) 
/*This will be called when we receive a SIGALRM*/ 
{ 
    int status; 
    printf("\nAssassin: *ksh* Received order to kill process: %d\n", (int)childPid); 
    if (!(status = kill(childPid, SIGKILL))) { 
     printf("Assassin: Clean and discreet. My work here is done. *ksh*\n"); 
    } else { 
     printf("Assassin: He got away!\n"); 
    } 
} 

void forkyMcFork(int secs) 
{ 
    pid_t pid; 
    int status; 
    /*Generate information for new program*/ 
    char* argv[] = {"problem5", "Hello"}; 
    char* envp[] = {"PANTS=JEANS"}; 
    char* func = "problem5"; 

    /* Create child process, child process calls executable "problem5" */ 
    if ((pid = Fork()) == 0) { 
     printf("Child: I am a child! Woohoo!\n"); 
     if (execve(func, argv, envp) < 0) 
      printf("Child: error, %s not found\n", func); 
     while(1); 
    } 
    else { 
     /* Parent process sets alarm, then prints a message depending on exit status*/ 
     childPid = pid; 
     alarm(secs); 
     printf("Parent: I am the parent!\n"); 
     waitpid(-1, &status, 0); 
     if (!WIFEXITED(status)) { 
      printf("Parent: Oh no, what happened to my baby!!!\n"); 
      exit(0); 
     } else { 
      printf("Parent: Child came home without any problems.\n"); 
     } 
    } 
} 

int main(int argc, char const *argv[]) 
{ 
    signal(SIGALRM, killhandler); 
    forkyMcFork(5); 
    return 0; 
} 

而这里的，输出：

$ ./forkfun 
Parent: I am the parent! 
Child: I am a child! Woohoo! 
Child: error, problem5 not found 

Assassin: *ksh* Received order to kill process: 42400 
Assassin: Clean and discreet. My work here is done. *ksh* 
Parent: Oh no, what happened to my baby!!! 
$ 

所以要清楚，这里唯一的代码区别在于是否forkyMcFork被声明为接受void ，在这种情况下它可以工作，或者采取int secs，在这种情况下它不会。这是怎么回事？

Answer 1

有鸭评论答案 - 所以只是总结：

INT的execve（为const char *文件名，char * const的ARGV []， char * const的envp []）;

argv是传递给新程序的参数字符串数组。 envp 是一个 字符串数组，通常为key = value形式，它们作为 环境传递给新程序。 argv和envp都必须以 空指针终止。

所以我建议添加NULL也终止envp。