在上一篇文章中，我们说到，C 语言系统应该由程序开发环境，C 语言本身和 C 语言的库组成。且同时说了程序开发环境做了“编写”，“预处理”，“编译”和“链接”这几件事情。但是细节并没有一一呈现。不知道同学们是否想过，这里都经历了一些什么呢？！
在这一篇文章中，我们就来看看“上帝说，要有光，就有了光。”是怎么实现的。假设你是上帝，想要实现“给我输出 'HELLO,WORLD!'”。同学们使用的 IDE 是 C-Free 5，这里的所有操作，都以此编译器为例。假设编译器安装路径为“C:\Program Files\C-Free 5”。
1. 代码编写
同学们已经上过第一节课了，我想，编写一个“HELLO,WORLD!”一定不成问题。代码本身是这样的：
1 #include <stdio.h>
2
3 int main(void)
4 {
5 printf("HELLO,WORLD!\n");
6 return 0;
7 }将此代码保存为“HelloWord.c”后准备下一步的处理。
2. 预处理
在保存了“HelloWord.c”文件夹中打开一个“cmd”窗口（按住 Shift 后右击选择“在此处打开命令窗口”），输入：
gcc -E HelloWorld.c -o HelloWorld.i
# 命令解释：
# 在 C-Free 5 身后，默默工作的就是这个名叫 gcc 的编译器了。
# 当输入上面的命令，紧跟其后的“-E”告知编译器想要做的是动作是仅做预处理这个动作。
# 然后后面跟随的“.c”文件告知 gcc 需要处理的文件的名称
# -o HelloWorld.i，是告诉编译器，输出一个文件，文件名就是“HelloWorld.i”
# （你看，计算机就是一个输入然后输出的系统吧）你会发现，在此目录下生成了一个名为“HelloWorld.i”的文件，打开文件，观察内容你会发现是这样的：
1 # 1 "HelloWorld.c"
2 # 1 "<built-in>"
3 # 1 "<command line>"
4 # 1 "HelloWorld.c"
5 # 1 "C:/Program Files (x86)/C-Free 5/mingw/bin/../lib/gcc/mingw32/3.4.5/../../../../include/stdio.h" 1 3
6 # 19 "C:/Program Files (x86)/C-Free 5/mingw/bin/../lib/gcc/mingw32/3.4.5/../../../../include/stdio.h" 3
7 # 1 "C:/Program Files (x86)/C-Free 5/mingw/bin/../lib/gcc/mingw32/3.4.5/../../../../include/_mingw.h" 1 3
8 # 27 "C:/Program Files (x86)/C-Free 5/mingw/bin/../lib/gcc/mingw32/3.4.5/../../../../include/_mingw.h" 3
9
10 # 28 "C:/Program Files (x86)/C-Free 5/mingw/bin/../lib/gcc/mingw32/3.4.5/../../../../include/_mingw.h" 3
11 # 20 "C:/Program Files (x86)/C-Free 5/mingw/bin/../lib/gcc/mingw32/3.4.5/../../../../include/stdio.h" 2 3
12
13
14
15
16
17
18 # 1 "C:/Program Files (x86)/C-Free 5/mingw/bin/../lib/gcc/mingw32/3.4.5/../../../../include/stddef.h" 1 3
19
20
21
22
23
24 # 1 "C:/Program Files (x86)/C-Free 5/mingw/bin/../lib/gcc/mingw32/3.4.5/include/stddef.h" 1 3 4
25 # 213 "C:/Program Files (x86)/C-Free 5/mingw/bin/../lib/gcc/mingw32/3.4.5/include/stddef.h" 3 4
26 typedef unsigned int size_t;
27 # 325 "C:/Program Files (x86)/C-Free 5/mingw/bin/../lib/gcc/mingw32/3.4.5/include/stddef.h" 3 4
28 typedef short unsigned int wchar_t;
29 # 354 "C:/Program Files (x86)/C-Free 5/mingw/bin/../lib/gcc/mingw32/3.4.5/include/stddef.h" 3 4
30 typedef short unsigned int wint_t;
31 # 7 "C:/Program Files (x86)/C-Free 5/mingw/bin/../lib/gcc/mingw32/3.4.5/../../../../include/stddef.h" 2 3
32 # 27 "C:/Program Files (x86)/C-Free 5/mingw/bin/../lib/gcc/mingw32/3.4.5/../../../../include/stdio.h" 2 3
33
34 # 1 "C:/Program Files (x86)/C-Free 5/mingw/bin/../lib/gcc/mingw32/3.4.5/../../../../include/stdarg.h" 1 3
35
36
37
38
39
40 # 1 "C:/Program Files (x86)/C-Free 5/mingw/bin/../lib/gcc/mingw32/3.4.5/include/stdarg.h" 1 3 4
41 # 44 "C:/Program Files (x86)/C-Free 5/mingw/bin/../lib/gcc/mingw32/3.4.5/include/stdarg.h" 3 4
42 typedef __builtin_va_list __gnuc_va_list;
43 # 7 "C:/Program Files (x86)/C-Free 5/mingw/bin/../lib/gcc/mingw32/3.4.5/../../../../include/stdarg.h" 2 3
44 # 29 "C:/Program Files (x86)/C-Free 5/mingw/bin/../lib/gcc/mingw32/3.4.5/../../../../include/stdio.h" 2 3
45 # 129 "C:/Program Files (x86)/C-Free 5/mingw/bin/../lib/gcc/mingw32/3.4.5/../../../../include/stdio.h" 3
46 typedef struct _iobuf
47 {
48 char* _ptr;
49 int _cnt;
50 char* _base;
51 int _flag;
52 int _file;
53 int _charbuf;
54 int _bufsiz;
55 char* _tmpfname;
56 } FILE;
57 # 154 "C:/Program Files (x86)/C-Free 5/mingw/bin/../lib/gcc/mingw32/3.4.5/../../../../include/stdio.h" 3
58 extern __attribute__ ((__dllimport__)) FILE _iob[];
59 # 169 "C:/Program Files (x86)/C-Free 5/mingw/bin/../lib/gcc/mingw32/3.4.5/../../../../include/stdio.h" 3
60 FILE* __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) fopen (const char*, const char*);
61 FILE* __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) freopen (const char*, const char*, FILE*);
62 int __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) fflush (FILE*);
63 int __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) fclose (FILE*);
64
65 int __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) remove (const char*);
66 int __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) rename (const char*, const char*);
67 FILE* __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) tmpfile (void);
68 char* __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) tmpnam (char*);
69
70
71 char* __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) _tempnam (const char*, const char*);
72 int __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) _rmtmp(void);
73 int __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) _unlink (const char*);
74
75
76 char* __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) tempnam (const char*, const char*);
77 int __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) rmtmp(void);
78 int __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) unlink (const char*);
79
80
81
82 int __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) setvbuf (FILE*, char*, int, size_t);
83
84 void __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) setbuf (FILE*, char*);
85
86
87
88
89
90 int __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) fprintf (FILE*, const char*, ...);
91 int __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) printf (const char*, ...);
92 int __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) sprintf (char*, const char*, ...);
93 int __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) _snprintf (char*, size_t, const char*, ...);
94 int __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) vfprintf (FILE*, const char*, __gnuc_va_list);
95 int __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) vprintf (const char*, __gnuc_va_list);
96 int __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) vsprintf (char*, const char*, __gnuc_va_list);
97 int __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) _vsnprintf (char*, size_t, const char*, __gnuc_va_list);
98 # 216 "C:/Program Files (x86)/C-Free 5/mingw/bin/../lib/gcc/mingw32/3.4.5/../../../../include/stdio.h" 3
99 int __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) snprintf(char *, size_t, const char *, ...);
100 int __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) vsnprintf (char *, size_t, const char *, __gnuc_va_list);
101
102 int __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) vscanf (const char * __restrict__, __gnuc_va_list);
103 int __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) vfscanf (FILE * __restrict__, const char * __restrict__,
104 __gnuc_va_list);
105 int __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) vsscanf (const char * __restrict__,
106 const char * __restrict__, __gnuc_va_list);
107
108
109
110
111
112
113
114 int __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) fscanf (FILE*, const char*, ...);
115 int __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) scanf (const char*, ...);
116 int __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) sscanf (const char*, const char*, ...);
117
118
119
120
121 int __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) fgetc (FILE*);
122 char* __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) fgets (char*, int, FILE*);
123 int __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) fputc (int, FILE*);
124 int __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) fputs (const char*, FILE*);
125 char* __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) gets (char*);
126 int __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) puts (const char*);
127 int __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) ungetc (int, FILE*);
128
129
130
131
132
133
134
135 int __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) _filbuf (FILE*);
136 int __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) _flsbuf (int, FILE*);
137
138
139
140 extern __inline__ int __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) getc (FILE* __F)
141 {
142 return (--__F->_cnt >= 0)
143 ? (int) (unsigned char) *__F->_ptr++
144 : _filbuf (__F);
145 }
146
147 extern __inline__ int __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) putc (int __c, FILE* __F)
148 {
149 return (--__F->_cnt >= 0)
150 ? (int) (unsigned char) (*__F->_ptr++ = (char)__c)
151 : _flsbuf (__c, __F);
152 }
153
154 extern __inline__ int __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) getchar (void)
155 {
156 return (--(&_iob[0])->_cnt >= 0)
157 ? (int) (unsigned char) *(&_iob[0])->_ptr++
158 : _filbuf ((&_iob[0]));
159 }
160
161 extern __inline__ int __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) putchar(int __c)
162 {
163 return (--(&_iob[1])->_cnt >= 0)
164 ? (int) (unsigned char) (*(&_iob[1])->_ptr++ = (char)__c)
165 : _flsbuf (__c, (&_iob[1]));}
166 # 297 "C:/Program Files (x86)/C-Free 5/mingw/bin/../lib/gcc/mingw32/3.4.5/../../../../include/stdio.h" 3
167 size_t __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) fread (void*, size_t, size_t, FILE*);
168 size_t __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) fwrite (const void*, size_t, size_t, FILE*);
169
170
171
172
173
174 int __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) fseek (FILE*, long, int);
175 long __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) ftell (FILE*);
176 void __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) rewind (FILE*);
177 # 340 "C:/Program Files (x86)/C-Free 5/mingw/bin/../lib/gcc/mingw32/3.4.5/../../../../include/stdio.h" 3
178 typedef long long fpos_t;
179
180
181
182
183 int __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) fgetpos (FILE*, fpos_t*);
184 int __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) fsetpos (FILE*, const fpos_t*);
185
186
187
188
189
190 int __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) feof (FILE*);
191 int __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) ferror (FILE*);
192 # 365 "C:/Program Files (x86)/C-Free 5/mingw/bin/../lib/gcc/mingw32/3.4.5/../../../../include/stdio.h" 3
193 void __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) clearerr (FILE*);
194 void __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) perror (const char*);
195
196
197
198
199
200
201 FILE* __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) _popen (const char*, const char*);
202 int __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) _pclose (FILE*);
203
204
205 FILE* __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) popen (const char*, const char*);
206 int __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) pclose (FILE*);
207
208
209
210
211
212 int __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) _flushall (void);
213 int __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) _fgetchar (void);
214 int __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) _fputchar (int);
215 FILE* __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) _fdopen (int, const char*);
216 int __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) _fileno (FILE*);
217 int __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) _fcloseall(void);
218 FILE* __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) _fsopen(const char*, const char*, int);
219
220 int __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) _getmaxstdio(void);
221 int __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) _setmaxstdio(int);
222 # 402 "C:/Program Files (x86)/C-Free 5/mingw/bin/../lib/gcc/mingw32/3.4.5/../../../../include/stdio.h" 3
223 int __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) fgetchar (void);
224 int __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) fputchar (int);
225 FILE* __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) fdopen (int, const char*);
226 int __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) fileno (FILE*);
227 # 414 "C:/Program Files (x86)/C-Free 5/mingw/bin/../lib/gcc/mingw32/3.4.5/../../../../include/stdio.h" 3
228 # 1 "C:/Program Files (x86)/C-Free 5/mingw/bin/../lib/gcc/mingw32/3.4.5/../../../../include/sys/types.h" 1 3
229 # 21 "C:/Program Files (x86)/C-Free 5/mingw/bin/../lib/gcc/mingw32/3.4.5/../../../../include/sys/types.h" 3
230 # 1 "C:/Program Files (x86)/C-Free 5/mingw/bin/../lib/gcc/mingw32/3.4.5/../../../../include/stddef.h" 1 3
231
232
233
234
235
236 # 1 "C:/Program Files (x86)/C-Free 5/mingw/bin/../lib/gcc/mingw32/3.4.5/include/stddef.h" 1 3 4
237 # 151 "C:/Program Files (x86)/C-Free 5/mingw/bin/../lib/gcc/mingw32/3.4.5/include/stddef.h" 3 4
238 typedef int ptrdiff_t;
239 # 7 "C:/Program Files (x86)/C-Free 5/mingw/bin/../lib/gcc/mingw32/3.4.5/../../../../include/stddef.h" 2 3
240 # 22 "C:/Program Files (x86)/C-Free 5/mingw/bin/../lib/gcc/mingw32/3.4.5/../../../../include/sys/types.h" 2 3
241
242
243
244
245
246 typedef long time_t;
247
248
249
250
251 typedef long long __time64_t;
252
253
254
255
256
257 typedef long _off_t;
258
259
260 typedef _off_t off_t;
261
262
263
264
265
266
267
268 typedef unsigned int _dev_t;
269
270
271
272
273
274 typedef _dev_t dev_t;
275
276
277
278
279
280
281 typedef short _ino_t;
282
283
284 typedef _ino_t ino_t;
285
286
287
288
289
290
291 typedef int _pid_t;
292
293
294 typedef _pid_t pid_t;
295
296
297
298
299
300
301 typedef unsigned short _mode_t;
302
303
304 typedef _mode_t mode_t;
305
306
307
308
309
310
311 typedef int _sigset_t;
312
313
314 typedef _sigset_t sigset_t;
315
316
317
318
319
320 typedef long _ssize_t;
321
322
323 typedef _ssize_t ssize_t;
324
325
326
327
328
329 typedef long long fpos64_t;
330
331
332
333
334 typedef long long off64_t;
335 # 415 "C:/Program Files (x86)/C-Free 5/mingw/bin/../lib/gcc/mingw32/3.4.5/../../../../include/stdio.h" 2 3
336 extern __inline__ FILE* __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) fopen64 (const char* filename, const char* mode)
337 {
338 return fopen (filename, mode);
339 }
340
341 int __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) fseeko64 (FILE*, off64_t, int);
342
343
344
345
346
347
348 extern __inline__ off64_t __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) ftello64 (FILE * stream)
349 {
350 fpos_t pos;
351 if (fgetpos(stream, &pos))
352 return -1LL;
353 else
354 return ((off64_t) pos);
355 }
356 # 443 "C:/Program Files (x86)/C-Free 5/mingw/bin/../lib/gcc/mingw32/3.4.5/../../../../include/stdio.h" 3
357 int __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) fwprintf (FILE*, const wchar_t*, ...);
358 int __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) wprintf (const wchar_t*, ...);
359 int __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) swprintf (wchar_t*, const wchar_t*, ...);
360 int __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) _snwprintf (wchar_t*, size_t, const wchar_t*, ...);
361 int __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) vfwprintf (FILE*, const wchar_t*, __gnuc_va_list);
362 int __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) vwprintf (const wchar_t*, __gnuc_va_list);
363 int __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) vswprintf (wchar_t*, const wchar_t*, __gnuc_va_list);
364 int __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) _vsnwprintf (wchar_t*, size_t, const wchar_t*, __gnuc_va_list);
365 int __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) fwscanf (FILE*, const wchar_t*, ...);
366 int __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) wscanf (const wchar_t*, ...);
367 int __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) swscanf (const wchar_t*, const wchar_t*, ...);
368 wint_t __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) fgetwc (FILE*);
369 wint_t __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) fputwc (wchar_t, FILE*);
370 wint_t __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) ungetwc (wchar_t, FILE*);
371
372
373 wchar_t* __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) fgetws (wchar_t*, int, FILE*);
374 int __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) fputws (const wchar_t*, FILE*);
375 wint_t __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) getwc (FILE*);
376 wint_t __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) getwchar (void);
377 wchar_t* __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) _getws (wchar_t*);
378 wint_t __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) putwc (wint_t, FILE*);
379 int __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) _putws (const wchar_t*);
380 wint_t __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) putwchar (wint_t);
381 FILE* __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) _wfdopen(int, wchar_t *);
382 FILE* __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) _wfopen (const wchar_t*, const wchar_t*);
383 FILE* __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) _wfreopen (const wchar_t*, const wchar_t*, FILE*);
384 FILE* __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) _wfsopen (const wchar_t*, const wchar_t*, int);
385 wchar_t* __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) _wtmpnam (wchar_t*);
386 wchar_t* __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) _wtempnam (const wchar_t*, const wchar_t*);
387 int __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) _wrename (const wchar_t*, const wchar_t*);
388 int __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) _wremove (const wchar_t*);
389 void __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) _wperror (const wchar_t*);
390 FILE* __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) _wpopen (const wchar_t*, const wchar_t*);
391
392
393
394 int __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) snwprintf (wchar_t* s, size_t n, const wchar_t* format, ...);
395 extern __inline__ int __attribute__((__cdecl__)) __attribute__ ((__nothrow__))
396 vsnwprintf (wchar_t* s, size_t n, const wchar_t* format, __gnuc_va_list arg)
397 { return _vsnwprintf ( s, n, format, arg);}
398 int __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) vwscanf (const wchar_t * __restrict__, __gnuc_va_list);
399 int __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) vfwscanf (FILE * __restrict__,
400 const wchar_t * __restrict__, __gnuc_va_list);
401 int __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) vswscanf (const wchar_t * __restrict__,
402 const wchar_t * __restrict__, __gnuc_va_list);
403 # 497 "C:/Program Files (x86)/C-Free 5/mingw/bin/../lib/gcc/mingw32/3.4.5/../../../../include/stdio.h" 3
404 FILE* __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) wpopen (const wchar_t*, const wchar_t*);
405
406
407
408
409
410
411 wint_t __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) _fgetwchar (void);
412 wint_t __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) _fputwchar (wint_t);
413 int __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) _getw (FILE*);
414 int __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) _putw (int, FILE*);
415
416
417 wint_t __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) fgetwchar (void);
418 wint_t __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) fputwchar (wint_t);
419 int __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) getw (FILE*);
420 int __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) putw (int, FILE*);
421 # 2 "HelloWorld.c" 2
422
423 int main(void)
424 {
425 printf("HELLO,WORLD!\n");
426 return 0;
427 }View Code
拖动到最底部，才能够发现我们最开始写的那几行代码。但是代码又和我们之前写的似而不同：
1 int __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) getw (FILE*);
2 int __attribute__((__cdecl__)) __attribute__ ((__nothrow__)) putw (int, FILE*);
3 # 2 "HelloWorld.c" 2
4
5 int main(void)
6 {
7 printf("HELLO,WORLD!\n");
8 return 0;
9 }可以发现，第一行的 #include <stdio.h> 却再也找不到了。其实，这就是预处理的功能，它会将你的代码中的 #include <XXXXXXX.h>
需要注意的是，预处理阶段，编译器 gcc 是不做语法上的检查的，比如我们写一段貌合神离的代码：
1 #include <stdio.h>
2
3 printf("HELLO,WORLD!\n");
然后重新执行上面的命令，你会发现，依旧会生成一个看似可用的“.i”文件。
3. 编译
编译阶段，编译器 gcc 将会对之前预处理生成的“.i”文件进行语法上的检查，看其是否符合 C 语言的语法规范，当检查通过以后，就进行编译的过程。这里，将其过程分为两步来看，首先，将预处理文件翻译为汇编文件：
1 gcc -S HelloWorld.i -o helloWorld.s
然后将汇编文件编译为目标文件：
1 gcc -c HelloWorld.s -o HelloWorld.obj
这里我们再来试试之前的“李鬼”代码，看看它能否通过流程，生成汇编文件：
1 gcc -S HelloWorld.i -o helloWorld.s
2 HelloWorldError.c:3: error: syntax error before string constant
3 HelloWorldError.c:3: error: conflicting types for 'printf'
4 HelloWorldError.c:3: note: a parameter list with an ellipsis can't match an empty parameter name list declaration
5 HelloWorldError.c:3: error: conflicting types for 'printf'
6 HelloWorldError.c:3: note: a parameter list with an ellipsis can't match an empty parameter name list declaration
7 HelloWorldError.c:3: warning: data definition has no type or storage class
哎呦，出了一堆的错误唉，有此可见，编译过程是需要执行内容的检查的，以确定其符合 C 语言的语法。
4. 链接
在上一步中，生成的目标文件“.obj”虽然本身也是二进制文件，但是其本身是不可执行的，需要对其进行链接。
1 gcc helloworld.obj -o helloworld.exe到这里，就生成可以执行的二进制文件了，赶快在终端中输入“HelloWorld”尝试运行吧：
虽然同学们可能直接在 C-Free 中仅需要点击一下按钮，后台就已经给你做了以上的这些事情，但是这里还是希望同学们能够理解这一过程（链接这一过程涉及到 C 语言库函数的事情，大家可以再扩展阅读哦）。
本文章为转载内容，我们尊重原作者对文章享有的著作权。如有内容错误或侵权问题，欢迎原作者联系我们进行内容更正或删除文章。
