小编use*_*007的帖子

我有一些代码使用 fork、execlp 和 wait 来创建两个进程。目标是能够重复打印提示并让用户输入命令，该命令最多包含 4 个参数/选项。

int main()
{
     string command, argument;
     istringstream iss(argument);

  do
  {
  //prompt user for command to run
  cout << "Enter command: ";
  cin >> command >> argument;

  int pid, rs, status;
 
  //fork will make 2 processes
  pid = fork();
  if(pid == -1) { perror("fork"); exit(EXIT_FAILURE); }

if(pid == 0) {
//Child process: exec to command with argument

//C_str to get the character string of a string
rs = execlp(command.c_str(), command.c_str(), argument.c_str(), (char*) NULL);
. …

我想使用自定义分配器从空闲列表中为std::basic_ostringstream. 这是我要使用的自定义分配器：

template <class Tp>

    struct NAlloc {
        typedef Tp value_type;
        typedef value_type* pointer;
        typedef const value_type* const_pointer;
        typedef value_type& reference;
        typedef const value_type& const_reference;
        typedef std::size_t size_type;
        typedef std::ptrdiff_t difference_type;

        NAlloc() = default;
        template <class T> NAlloc(const NAlloc<T>&) {}
        Tp* allocate(std::size_t n) {
            n *= sizeof(Tp);
            memoryPool *memPool = memoryPool::GetInstance(10);//get memory pool instance
            std::cout << "allocating " << n << " bytes\n";
            return static_cast<Tp*>(memPool->allocate(n)); //get memory from pool
        }
        void deallocate(Tp* p, std::size_t n) {
            std::cout << …