c - 使用 vfork() 对子级数求和

Question

我想用 vfork() 编写一个程序，父级创建 n 个子级，我想用参数插入儿子的数量。然后我想计算儿子的数量，例如:

./sum 4
The sum of the child: 10
The sum of the parent: 10

(1+2+3+4)

这是我想出的小代码，但我得到了无限循环。

int n = atoi(argv[1]);
int i = 1;
pid_t pid;
int sumchild = 0;
int sumparent = 0;

    while(i <= n){
        pid = vfork();
        if(pid == 0){
            sumchild = sumchild + i;        
        }

        i++;
    }
    printf("The sum of the child: %i ", sumchild);

    sumparent = (1 + n) * (n / 2);
    printf("The sum of the parent: %i \n", sumparent);

我听说你不需要像 fork() 中那样的 wait()，但我不知道为什么这里会出现无限循环。

我应该如何使用vfork()？我写的代码是正确的还是犯了一些错误？

Answer 1

以下代码

    pid = vfork();
    if(pid == 0){
        sumchild = sumchild + i; 

将导致未定义的行为，根据vfork :

The vfork() function has the same effect as fork(2), except that the behavior is undefined if the process created by vfork() either modifies any data other than a variable of type pid_t used to store the return value from vfork(), or returns from the function in which vfork() was called, or calls any other function before successfully calling _exit(2) or one of the exec(3) family of functions.