我也要学C语言(威力加强版)_第一章：WINDOWS平台下CL编译器下helloworld的编写,编译与链接
Posted on 2011-08-16 20:01 dodolook 阅读(5612) 评论(34) 编辑 收藏 举报编辑器，编译器，调试器的选择：
在WINDOWS平台下编译C程序有很多种编译器可以选择，比如gcc,cl,intel c++等等。编辑器呢！那就更多了，但是有2个编辑器做为主要的推荐，1个是vim,1个是emacs.任选其1就好了。调试器的话，你可以选择gdb,还有vc集成开发环境的调试器。gdb别看它黑乎乎的哦！很是强大的，不过你不习惯黑乎乎的命令行界面，也可以选择一些gdb的图形前端。vc集成开发环境的调试器呢！也非常的强大，很直观。不过这2款调试器，我比较偏爱gdb.
用vim编写C语言helloworld代码：
vim的上手可以参考其帮助文档，启动vim后输入命令:help 如图：
通过这一帮助文件就可以让你很快的上手vim.当然要更好的在vim写C程序你可以参考网络上相关的windows下vim c++开发环境的搭建文献。
呵呵！下面开始在vim中写代码了!
要理解好这个程序呢！必须先要明白一个概念，就是一个程序到底是如何被编写，编译，链接和执行的，这一过程可以参考下面的图：
首先，我们刚才在VIM中编写了helloworld的源代码了，下一步就是编译了。如图：
可以看到一个cl命令后，编译器自动完成了编译链接的过程。下面结合代码一步一步的去理解这一整个过程。
第一行！很多人做事情都有自己的一个工具包！比如修电路的大叔！一般都挎着一个电工包！木匠呢，也有一个工具包，里面放着一些常用的工具。嘿嘿！那么，现在我是想在屏幕上输出helloworld!这个时候呢，我就需要1个输出包啦！所以#include<stdio.h>就表示把stdio.h文件包拿来用，<>是表示从哪里去拿。#include就是表示这里这个位置开始插入包（其实本质是复制粘帖）。嘿嘿！我明白了！stdio.h里啦就定义实现如何输出的了！其实这个stdio.h里了不是只有输出工具的，还有输入等工具！所以这里的代码其实是把所有stdio.h里面的工具包全拿过来了！（看起来有点浪费啊！唉！）。那么如何查看这一预处理后的文件呢，这里我们加入1个参数/P.就会出现1个.i的文件了，我们来看看：
嘿嘿！出来了吧！我们再打开这个.i文件看看：
View Code
#line 1 "helloworld.c"
#line 1 "E:\\vc6.0\\VC98\\Include\\stdio.h"
#pragma once
#line 18 "E:\\vc6.0\\VC98\\Include\\stdio.h"
#line 25 "E:\\vc6.0\\VC98\\Include\\stdio.h"
#pragma pack(push,8)
#line 34 "E:\\vc6.0\\VC98\\Include\\stdio.h"
#line 49 "E:\\vc6.0\\VC98\\Include\\stdio.h"
#line 50 "E:\\vc6.0\\VC98\\Include\\stdio.h"
#line 57 "E:\\vc6.0\\VC98\\Include\\stdio.h"
#line 66 "E:\\vc6.0\\VC98\\Include\\stdio.h"
#line 67 "E:\\vc6.0\\VC98\\Include\\stdio.h"
typedef unsigned int size_t;
#line 73 "E:\\vc6.0\\VC98\\Include\\stdio.h"
typedef unsigned short wchar_t;
#line 80 "E:\\vc6.0\\VC98\\Include\\stdio.h"
typedef wchar_t wint_t;
typedef wchar_t wctype_t;
#line 87 "E:\\vc6.0\\VC98\\Include\\stdio.h"
#line 88 "E:\\vc6.0\\VC98\\Include\\stdio.h"
typedef char * va_list;
#line 99 "E:\\vc6.0\\VC98\\Include\\stdio.h"
#line 101 "E:\\vc6.0\\VC98\\Include\\stdio.h"
#line 108 "E:\\vc6.0\\VC98\\Include\\stdio.h"
#line 110 "E:\\vc6.0\\VC98\\Include\\stdio.h"
#line 141 "E:\\vc6.0\\VC98\\Include\\stdio.h"
struct _iobuf {
char *_ptr;
int _cnt;
char *_base;
int _flag;
int _file;
int _charbuf;
int _bufsiz;
char *_tmpfname;
};
typedef struct _iobuf FILE;
#line 159 "E:\\vc6.0\\VC98\\Include\\stdio.h"
#line 172 "E:\\vc6.0\\VC98\\Include\\stdio.h"
#line 185 "E:\\vc6.0\\VC98\\Include\\stdio.h"
#line 214 "E:\\vc6.0\\VC98\\Include\\stdio.h"
#line 215 "E:\\vc6.0\\VC98\\Include\\stdio.h"
extern FILE _iob[];
#line 222 "E:\\vc6.0\\VC98\\Include\\stdio.h"
#line 232 "E:\\vc6.0\\VC98\\Include\\stdio.h"
typedef __int64 fpos_t;
#line 243 "E:\\vc6.0\\VC98\\Include\\stdio.h"
#line 244 "E:\\vc6.0\\VC98\\Include\\stdio.h"
#line 247 "E:\\vc6.0\\VC98\\Include\\stdio.h"
int __cdecl _filbuf(FILE *);
int __cdecl _flsbuf(int, FILE *);
FILE * __cdecl _fsopen(const char *, const char *, int);
#line 283 "E:\\vc6.0\\VC98\\Include\\stdio.h"
void __cdecl clearerr(FILE *);
int __cdecl fclose(FILE *);
int __cdecl _fcloseall(void);
FILE * __cdecl _fdopen(int, const char *);
#line 293 "E:\\vc6.0\\VC98\\Include\\stdio.h"
int __cdecl feof(FILE *);
int __cdecl ferror(FILE *);
int __cdecl fflush(FILE *);
int __cdecl fgetc(FILE *);
int __cdecl _fgetchar(void);
int __cdecl fgetpos(FILE *, fpos_t *);
char * __cdecl fgets(char *, int, FILE *);
int __cdecl _fileno(FILE *);
#line 307 "E:\\vc6.0\\VC98\\Include\\stdio.h"
int __cdecl _flushall(void);
FILE * __cdecl fopen(const char *, const char *);
int __cdecl fprintf(FILE *, const char *, ...);
int __cdecl fputc(int, FILE *);
int __cdecl _fputchar(int);
int __cdecl fputs(const char *, FILE *);
size_t __cdecl fread(void *, size_t, size_t, FILE *);
FILE * __cdecl freopen(const char *, const char *, FILE *);
int __cdecl fscanf(FILE *, const char *, ...);
int __cdecl fsetpos(FILE *, const fpos_t *);
int __cdecl fseek(FILE *, long, int);
long __cdecl ftell(FILE *);
size_t __cdecl fwrite(const void *, size_t, size_t, FILE *);
int __cdecl getc(FILE *);
int __cdecl getchar(void);
int __cdecl _getmaxstdio(void);
char * __cdecl gets(char *);
int __cdecl _getw(FILE *);
void __cdecl perror(const char *);
int __cdecl _pclose(FILE *);
FILE * __cdecl _popen(const char *, const char *);
int __cdecl printf(const char *, ...);
int __cdecl putc(int, FILE *);
int __cdecl putchar(int);
int __cdecl puts(const char *);
int __cdecl _putw(int, FILE *);
int __cdecl remove(const char *);
int __cdecl rename(const char *, const char *);
void __cdecl rewind(FILE *);
int __cdecl _rmtmp(void);
int __cdecl scanf(const char *, ...);
void __cdecl setbuf(FILE *, char *);
int __cdecl _setmaxstdio(int);
int __cdecl setvbuf(FILE *, char *, int, size_t);
int __cdecl _snprintf(char *, size_t, const char *, ...);
int __cdecl sprintf(char *, const char *, ...);
int __cdecl sscanf(const char *, const char *, ...);
char * __cdecl _tempnam(const char *, const char *);
FILE * __cdecl tmpfile(void);
char * __cdecl tmpnam(char *);
int __cdecl ungetc(int, FILE *);
int __cdecl _unlink(const char *);
int __cdecl vfprintf(FILE *, const char *, va_list);
int __cdecl vprintf(const char *, va_list);
int __cdecl _vsnprintf(char *, size_t, const char *, va_list);
int __cdecl vsprintf(char *, const char *, va_list);
#line 363 "E:\\vc6.0\\VC98\\Include\\stdio.h"
FILE * __cdecl _wfsopen(const wchar_t *, const wchar_t *, int);
#line 369 "E:\\vc6.0\\VC98\\Include\\stdio.h"
wint_t __cdecl fgetwc(FILE *);
wint_t __cdecl _fgetwchar(void);
wint_t __cdecl fputwc(wint_t, FILE *);
wint_t __cdecl _fputwchar(wint_t);
wint_t __cdecl getwc(FILE *);
wint_t __cdecl getwchar(void);
wint_t __cdecl putwc(wint_t, FILE *);
wint_t __cdecl putwchar(wint_t);
wint_t __cdecl ungetwc(wint_t, FILE *);
wchar_t * __cdecl fgetws(wchar_t *, int, FILE *);
int __cdecl fputws(const wchar_t *, FILE *);
wchar_t * __cdecl _getws(wchar_t *);
int __cdecl _putws(const wchar_t *);
int __cdecl fwprintf(FILE *, const wchar_t *, ...);
int __cdecl wprintf(const wchar_t *, ...);
int __cdecl _snwprintf(wchar_t *, size_t, const wchar_t *, ...);
int __cdecl swprintf(wchar_t *, const wchar_t *, ...);
int __cdecl vfwprintf(FILE *, const wchar_t *, va_list);
int __cdecl vwprintf(const wchar_t *, va_list);
int __cdecl _vsnwprintf(wchar_t *, size_t, const wchar_t *, va_list);
int __cdecl vswprintf(wchar_t *, const wchar_t *, va_list);
int __cdecl fwscanf(FILE *, const wchar_t *, ...);
int __cdecl swscanf(const wchar_t *, const wchar_t *, ...);
int __cdecl wscanf(const wchar_t *, ...);
FILE * __cdecl _wfdopen(int, const wchar_t *);
FILE * __cdecl _wfopen(const wchar_t *, const wchar_t *);
FILE * __cdecl _wfreopen(const wchar_t *, const wchar_t *, FILE *);
void __cdecl _wperror(const wchar_t *);
FILE * __cdecl _wpopen(const wchar_t *, const wchar_t *);
int __cdecl _wremove(const wchar_t *);
wchar_t * __cdecl _wtempnam(const wchar_t *, const wchar_t *);
wchar_t * __cdecl _wtmpnam(wchar_t *);
#line 414 "E:\\vc6.0\\VC98\\Include\\stdio.h"
#line 415 "E:\\vc6.0\\VC98\\Include\\stdio.h"
#line 418 "E:\\vc6.0\\VC98\\Include\\stdio.h"
int __cdecl fcloseall(void);
FILE * __cdecl fdopen(int, const char *);
int __cdecl fgetchar(void);
int __cdecl fileno(FILE *);
int __cdecl flushall(void);
int __cdecl fputchar(int);
int __cdecl getw(FILE *);
int __cdecl putw(int, FILE *);
int __cdecl rmtmp(void);
char * __cdecl tempnam(const char *, const char *);
int __cdecl unlink(const char *);
#line 463 "E:\\vc6.0\\VC98\\Include\\stdio.h"
#pragma pack(pop)
#line 471 "E:\\vc6.0\\VC98\\Include\\stdio.h"
#line 473 "E:\\vc6.0\\VC98\\Include\\stdio.h"
#line 2 "helloworld.c"
void main()
{
printf("Helloworld!\n");
}
第三行！void main()，这行呢，先要说明下了！一个很特别的单词main后面还跟着个()。其实这样的形式在C语言就是表示函数，前面的int就是函数的返回值了！其实函数也就像1个工具包里的一个有生命的小工具！你给它喂点东西，比如这里喂void，而且还要让它吐出1个int类型的东西出来！嘿嘿！而且这个有生命的小工具是可以反复使用的！但是这里有点特殊！用main命名的小工具一般只用1次，因为它有个特殊的使命啊！！！它是用户的入门函数！其实呢在VC上面真正的入门函数是mainCRTStartup()，在用户入门函数main()之前到mainCRTStartup()中间呢其实已经做了好多工作了！比如有准备命令行，获得操作系统版本,IO的初始化,获得环境选项以及其字符串，全局变量的初始化，还有做了条件编译！如果是Win程序的话入口就是WinMain(),如果不是入口就是main()啦！然后main()执行完了程序才exit啦！其实main()函数是倒数第二条函数了！不过呢一般来说，程序员有操作权限的就是到了main()函数这里了！这一过程你可以打开crt0.c文件看看具体代码如下：
View Code
/***
*crt0.c - C runtime initialization routine
*
* Copyright (c) 1989-1997, Microsoft Corporation. All rights reserved.
*
*Purpose:
* This the actual startup routine for apps. It calls the user's main
* routine [w]main() or [w]WinMain after performing C Run-Time Library
* initialization.
*
* (With ifdef's, this source file also provides the source code for
* wcrt0.c, the startup routine for console apps with wide characters,
* wincrt0.c, the startup routine for Windows apps, and wwincrt0.c,
* the startup routine for Windows apps with wide characters.)
*
*******************************************************************************/
#ifdef _WIN32
#ifndef CRTDLL
#include <cruntime.h>
#include <dos.h>
#include <internal.h>
#include <stdlib.h>
#include <string.h>
#include <rterr.h>
#include <windows.h>
#include <awint.h>
#include <tchar.h>
#include <dbgint.h>
/*
* wWinMain is not yet defined in winbase.h. When it is, this should be
* removed.
*/
int
WINAPI
wWinMain(
HINSTANCE hInstance,
HINSTANCE hPrevInstance,
LPWSTR lpCmdLine,
int nShowCmd
);
#ifdef WPRFLAG
_TUCHAR * __cdecl _wwincmdln(void);
#else /* WPRFLAG */
_TUCHAR * __cdecl _wincmdln(void);
#endif /* WPRFLAG */
/*
* command line, environment, and a few other globals
*/
#ifdef WPRFLAG
wchar_t *_wcmdln; /* points to wide command line */
#else /* WPRFLAG */
char *_acmdln; /* points to command line */
#endif /* WPRFLAG */
char *_aenvptr = NULL; /* points to environment block */
wchar_t *_wenvptr = NULL; /* points to wide environment block */
void (__cdecl * _aexit_rtn)(int) = _exit; /* RT message return procedure */
static void __cdecl fast_error_exit(int); /* Error exit via ExitProcess */
/*
* _error_mode and _apptype, together, determine how error messages are
* written out.
*/
int __error_mode = _OUT_TO_DEFAULT;
#ifdef _WINMAIN_
int __app_type = _GUI_APP;
#else /* _WINMAIN_ */
int __app_type = _CONSOLE_APP;
#endif /* _WINMAIN_ */
/***
*BaseProcessStartup(PVOID Peb)
*
*Purpose:
* This routine does the C runtime initialization, calls main(), and
* then exits. It never returns.
*
*Entry:
* PVOID Peb - pointer to Win32 Process Environment Block (not used)
*
*Exit:
* This function never returns.
*
*******************************************************************************/
#ifdef _WINMAIN_
#ifdef WPRFLAG
void wWinMainCRTStartup(
#else /* WPRFLAG */
void WinMainCRTStartup(
#endif /* WPRFLAG */
#else /* _WINMAIN_ */
#ifdef WPRFLAG
void wmainCRTStartup(
#else /* WPRFLAG */
void mainCRTStartup(
#endif /* WPRFLAG */
#endif /* _WINMAIN_ */
void
)
{
int mainret;
#ifdef _WINMAIN_
_TUCHAR *lpszCommandLine;
STARTUPINFO StartupInfo;
#endif /* _WINMAIN_ */
/*
* Get the full Win32 version
*/
_osver = GetVersion();
_winminor = (_osver >> 8) & 0x00FF ;
_winmajor = _osver & 0x00FF ;
_winver = (_winmajor << 8) + _winminor;
_osver = (_osver >> 16) & 0x00FFFF ;
#ifdef _MT
if ( !_heap_init(1) ) /* initialize heap */
#else /* _MT */
if ( !_heap_init(0) ) /* initialize heap */
#endif /* _MT */
fast_error_exit(_RT_HEAPINIT); /* write message and die */
#ifdef _MT
if( !_mtinit() ) /* initialize multi-thread */
fast_error_exit(_RT_THREAD); /* write message and die */
#endif /* _MT */
/*
* Guard the remainder of the initialization code and the call
* to user's main, or WinMain, function in a __try/__except
* statement.
*/
__try {
_ioinit(); /* initialize lowio */
#ifdef WPRFLAG
/* get wide cmd line info */
_wcmdln = (wchar_t *)__crtGetCommandLineW();
/* get wide environ info */
_wenvptr = (wchar_t *)__crtGetEnvironmentStringsW();
_wsetargv();
_wsetenvp();
#else /* WPRFLAG */
/* get cmd line info */
_acmdln = (char *)GetCommandLineA();
/* get environ info */
_aenvptr = (char *)__crtGetEnvironmentStringsA();
_setargv();
_setenvp();
#endif /* WPRFLAG */
_cinit(); /* do C data initialize */
#ifdef _WINMAIN_
StartupInfo.dwFlags = 0;
GetStartupInfo( &StartupInfo );
#ifdef WPRFLAG
lpszCommandLine = _wwincmdln();
mainret = wWinMain(
#else /* WPRFLAG */
lpszCommandLine = _wincmdln();
mainret = WinMain(
#endif /* WPRFLAG */
GetModuleHandleA(NULL),
NULL,
lpszCommandLine,
StartupInfo.dwFlags & STARTF_USESHOWWINDOW
? StartupInfo.wShowWindow
: SW_SHOWDEFAULT
);
#else /* _WINMAIN_ */
#ifdef WPRFLAG
__winitenv = _wenviron;
mainret = wmain(__argc, __wargv, _wenviron);
#else /* WPRFLAG */
__initenv = _environ;
mainret = main(__argc, __argv, _environ);
#endif /* WPRFLAG */
#endif /* _WINMAIN_ */
exit(mainret);
}
__except ( _XcptFilter(GetExceptionCode(), GetExceptionInformation()) )
{
/*
* Should never reach here
*/
_exit( GetExceptionCode() );
} /* end of try - except */
}
/***
*_amsg_exit(rterrnum) - Fast exit fatal errors
*
*Purpose:
* Exit the program with error code of 255 and appropriate error
* message.
*
*Entry:
* int rterrnum - error message number (amsg_exit only).
*
*Exit:
* Calls exit() (for integer divide-by-0) or _exit() indirectly
* through _aexit_rtn [amsg_exit].
* For multi-thread: calls _exit() function
*
*Exceptions:
*
*******************************************************************************/
void __cdecl _amsg_exit (
int rterrnum
)
{
#ifdef _WINMAIN_
if ( __error_mode == _OUT_TO_STDERR )
#else /* _WINMAIN_ */
if ( __error_mode != _OUT_TO_MSGBOX )
#endif /* _WINMAIN_ */
_FF_MSGBANNER(); /* write run-time error banner */
_NMSG_WRITE(rterrnum); /* write message */
_aexit_rtn(255); /* normally _exit(255) */
}
/***
*fast_error_exit(rterrnum) - Faster exit fatal errors
*
*Purpose:
* Exit the process with error code of 255 and appropriate error
* message.
*
*Entry:
* int rterrnum - error message number (amsg_exit only).
*
*Exit:
* Calls ExitProcess.
*
*Exceptions:
*
*******************************************************************************/
static void __cdecl fast_error_exit (
int rterrnum
)
{
#ifdef _WINMAIN_
if ( __error_mode == _OUT_TO_STDERR )
#else /* _WINMAIN_ */
if ( __error_mode != _OUT_TO_MSGBOX )
#endif /* _WINMAIN_ */
_FF_MSGBANNER(); /* write run-time error banner */
_NMSG_WRITE(rterrnum); /* write message */
ExitProcess(255); /* normally _exit(255) */
}
#ifndef WPRFLAG
#endif /* WPRFLAG */
#endif /* CRTDLL */
#else /* _WIN32 */
#include <cruntime.h>
#include <internal.h>
#include <stdlib.h>
#include <msdos.h>
#include <string.h>
#include <setjmp.h>
#include <dbgint.h>
#include <macos\types.h>
#include <macos\segload.h>
#include <macos\gestalte.h>
#include <macos\osutils.h>
#include <macos\traps.h>
#include <mpw.h>
static void __cdecl Inherit(void); /* local function */
int __cdecl main(int, char **, char **); /*generated by compiler*/
unsigned long _GetShellStack(void);
static char * __cdecl _p2cstr_internal ( unsigned char * str );
extern MPWBLOCK * _pMPWBlock;
extern int __argc;
extern char **__argv;
/***
*__crt0()
*
*Purpose:
* This routine does the C runtime initialization, calls main(), and
* then exits. It never returns.
*
*Entry:
*
*Exit:
* This function never returns.
*
*******************************************************************************/
void __cdecl __crt0 (
)
{
int mainret;
char szPgmName[32];
char *pArg;
char *argv[2];
#ifndef _M_MPPC
void *pv;
/* This is the magic stuff that MPW tools do to get info from MPW*/
pv = (void *)*(int *)0x316;
if (pv != NULL && !((int)pv & 1) && *(int *)pv == 'MPGM') {
pv = (void *)*++(int *)pv;
if (pv != NULL && *(short *)pv == 'SH') {
_pMPWBlock = (MPWBLOCK *)pv;
}
}
#endif /* _M_MPPC */
_environ = NULL;
if (_pMPWBlock == NULL) {
__argc = 1;
memcpy(szPgmName, (char *)0x910, sizeof(szPgmName));
pArg = _p2cstr_internal(szPgmName);
argv[0] = pArg;
argv[1] = NULL;
__argv = argv;
#ifndef _M_MPPC
_shellStack = 0; /* force ExitToShell */
#endif /* _M_MPPC */
}
#ifndef _M_MPPC
else {
_shellStack = _GetShellStack(); //return current a6, or first a6
_shellStack += 4; //a6 + 4 is the stack pointer we want
__argc = _pMPWBlock->argc;
__argv = _pMPWBlock->argv;
Inherit(); /* Inherit file handles - env is set up by _envinit if needed */
}
#endif /* _M_MPPC */
/*
* call run time initializer
*/
__cinit();
mainret = main(__argc, __argv, _environ);
exit(mainret);
}
#ifndef _M_MPPC
/***
*Inherit() - obtain and process info on inherited file handles.
*
*Purpose:
*
* Locates and interprets MPW std files. For files we just save the
* file handles. For the console we save the device table address so
* we can do console I/O. In the latter case, FDEV is set in the _osfile
* array.
*
*Entry:
* Address of MPW param table
*
*Exit:
* No return value.
*
*Exceptions:
*
*******************************************************************************/
static void __cdecl Inherit (
void
)
{
MPWFILE *pFile;
int i;
pFile = _pMPWBlock->pFile;
if (pFile == NULL) {
return;
}
for (i = 0; i < 3; i++) {
switch ((pFile->pDevice)->name) {
case 'ECON':
_osfile[i] |= FDEV | FOPEN;
_osfhnd[i] = (int)pFile;
break;
case 'FSYS':
_osfile[i] |= FOPEN;
_osfhnd[i] = (*(pFile->ppFInfo))->ioRefNum;
break;
}
pFile++;
}
}
#endif /* _M_MPPC */
static char * __cdecl _p2cstr_internal (
unsigned char * str
)
{
unsigned char *pchSrc;
unsigned char *pchDst;
int cch;
if ( str && *str ) {
pchDst = str;
pchSrc = str + 1;
for ( cch=*pchDst; cch; --cch ) {
*pchDst++ = *pchSrc++;
}
*pchDst = '\0';
}
return( str );
}
#endif /* _WIN32 */
第四行和第六行！诶！为什么这两行要一起学啊！因为这两行只有2个括号！哈哈！在C语言中呢1对括号就代表1个代码块了！就像python的缩进了！（应该是这样吧！以后学多了或许有新感悟的！暂时就这样理解吧！）
第五行！这一行呢其实就是从stdio.h中取出printf输出这个小工具(函数)了，然后用这个工具在屏幕上打印helloworld!字符串了！哦！很神奇！这个工具好啊！但是目前鉴于自己的水平，还不能很好的解释printf的实现，以后再解释了！
关于cl的命令行参数可以参考msdn,上面有详细的参数帮助目录。
