cout internal

先看看cout是这么定义的： istream cout(&fout)

//C:\Program Files (x86)\Microsoft Visual Studio 10.0\VC\crt\src\cout.cpp

// cout -- initialize standard output stream
#include <fstream>
#include <iostream>#pragma warning(disable: 4074)
#pragma init_seg(compiler)
static std::_Init_locks  initlocks;_STD_BEGIN// OBJECT DECLARATIONS

__PURE_APPDOMAIN_GLOBAL static filebuf fout(_cpp_stdout);
#if defined(_M_CEE_PURE)
__PURE_APPDOMAIN_GLOBAL extern ostream cout(&fout);
#else
__PURE_APPDOMAIN_GLOBAL extern _CRTDATA2 ostream cout(&fout);
#endif// INITIALIZATION CODE
struct _Init_cout{   // ensures that cout is initialized
    __CLR_OR_THIS_CALL _Init_cout(){   // initialize cout
        _Ptr_cout = &cout;if (_Ptr_cin != 0)_Ptr_cin->tie(_Ptr_cout);if (_Ptr_cerr != 0)_Ptr_cerr->tie(_Ptr_cout);if (_Ptr_clog != 0)_Ptr_clog->tie(_Ptr_cout);}};
__PURE_APPDOMAIN_GLOBAL static _Init_cout init_cout;_STD_END/** Copyright (c) 1992-2007 by P.J. Plauger.  ALL RIGHTS RESERVED.* Consult your license regarding permissions and restrictions.V5.03:0009 */

再看看 _cpp_stdout 是怎么回事？

//C:\Program Files (x86)\Microsoft Visual Studio 10.0\VC\crt\src\yvals.h

   #define _cpp_stdin  (&(__iob_func())[0])
   #define _cpp_stdout (&(__iob_func())[1])
   #define _cpp_stderr (&(__iob_func())[2])
   #define _cpp_isleadbyte(c) (__pctype_func()[(unsigned char)(c)] & _LEADBYTE)

关于 __iob_func(): __iob_func() returns a pointer to the array of FILE descriptors that holds stdin, stdout, stderr and any FILE objects opened through the C runtime library. See the MSVC runtime library source _file.c.

//C:\Program Files (x86)\Microsoft Visual Studio 10.0\VC\crt\src\_file.c

/** FILE descriptors; preset for stdin/out/err (note that the __tmpnum field* is not initialized)*/
FILE _iob[_IOB_ENTRIES] = {/* _ptr, _cnt, _base,  _flag, _file, _charbuf, _bufsiz *//* stdin (_iob[0]) */{ _bufin, 0, _bufin, _IOREAD | _IOYOURBUF, 0, 0, _INTERNAL_BUFSIZ },/* stdout (_iob[1]) */{ NULL, 0, NULL, _IOWRT, 1, 0, 0 },/* stderr (_iob[3]) */{ NULL, 0, NULL, _IOWRT, 2, 0, 0 },};/** Initializer and terminator for stdio*/
int  __cdecl __initstdio(void);
void __cdecl __endstdio(void);_CRTALLOC(".CRT$XIC") static _PIFV pinit = __initstdio;_CRTALLOC(".CRT$XPXA") static _PVFV pterm = __endstdio;

//C:\Program Files (x86)\Microsoft Visual Studio 10.0\VC\crt\src\internal.h

struct _iobuf {char *_ptr;int   _cnt;char *_base;int   _flag;int   _file;int   _charbuf;int   _bufsiz;char *_tmpfname;};
typedef struct _iobuf FILE;

Post by: Jalen Wang (转载请注明出处)