c++ - 从 void* 到 int* 的无效转换

Question

我有一个全局变量:

static int *avgg;

在主函数中:

avgg = mmap(NULL, sizeof *avgg, PROT_READ | PROT_WRITE, 
                MAP_SHARED | MAP_ANONYMOUS, -1, 0);

pid_t  pid, wpid;
int status;

 pid = fork();
 if (pid == 0) {
      avg(argc,argv);
      print_avg();

  }
 else{ 
     while ((wpid = wait(&status)) > 0) {

     }
 cout<<"Parent process";
     print_avg();

通过使用 mmap，我试图在父进程和子进程之间共享内存，但出现错误:

invalid conversion from ‘void*’ to ‘int*’ [-fpermissive]
                 MAP_SHARED | MAP_ANONYMOUS, -1, 0);

Answer 1

您正试图将 mmap 的返回值(void *)隐式转换为 int *，而您的编译器设置不允许您在没有显式转换的情况下这样做。

尝试 avgg = (int *)mmap(NULL, sizeof *avgg, PROT_READ | PROT_WRITE, MAP_SHARED | MAP_ANONYMOUS, -1, 0);