cin的数据类型是什么

Question

我想知道cin到底是什么。我的意思是一个函数或 class.....

我确定它不是函数，因为我们使用 cin 的方式与调用 a 函数的方式非常不同。

剩下 class 或对象或其他选项。

具体是什么？

Answer 1

cin 是对象的 istream class

Answer 2

C++ 标准 §27.4.1 [iostream.objects.overview]

#include <ios>
#include <streambuf>
#include <istream>
#include <ostream>

namespace std {
  extern istream cin;
  extern ostream cout;
  extern ostream cerr;
  extern ostream clog;
  extern wistream wcin;
  extern wostream wcout;
  extern wostream wcerr;
  extern wostream wclog;
}
p1 The header declares objects that associate objects with the standard C streams provided for by the functions declared in (27.9.2), and includes all the headers necessary to use these objects.

你也可以看看 gcc 的 implementation on github:

namespace std _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION

  // Standard stream objects.
  // NB: Iff <iostream> is included, these definitions become wonky.
  typedef char fake_istream[sizeof(istream)]
  __attribute__ ((aligned(__alignof__(istream))));
  typedef char fake_ostream[sizeof(ostream)]
  __attribute__ ((aligned(__alignof__(ostream))));
  fake_istream cin;
  fake_ostream cout;
  fake_ostream cerr;
  fake_ostream clog;

#ifdef _GLIBCXX_USE_WCHAR_T
  typedef char fake_wistream[sizeof(wistream)]
  __attribute__ ((aligned(__alignof__(wistream))));
  typedef char fake_wostream[sizeof(wostream)]
  __attribute__ ((aligned(__alignof__(wostream))));
  fake_wistream wcin;
  fake_wostream wcout;
  fake_wostream wcerr;
  fake_wostream wclog;
#endif

_GLIBCXX_END_NAMESPACE_VERSION
} // namespace

cin的数据类型是什么

What is datatype of cin

c++

cin