cout internal

时间：2021-03-01 15:27:26

cout internal

*/-->

pre {
background-color: #2f4f4f;line-height: 1.6;
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.h3 {
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}

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)

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