我发现lex&&yacc上的代码在flex下编译出错

Question

第二章的ch2-05.l:

2. %{
3. #undef input
4. #undef unput
5. int input(void);
6. void unput(int ch);
7. unsigned verbose;
8. char *progName;
9. %}
11. %%
13. -h        |
14. "-?"        |
15. -help        { printf("usage is: %s [-help | -h | -? ] [-verbose | -v]"
16.          " [(-file| -f) filename]\n", progName);
17.         }
18. -v        |
19. -verbose { printf("verbose mode is on\n"); verbose = 1; }
21. %%
22. char **targv;        /* remembers arguments */
23. char **arglim;        /* end of arguments */
25. main(int argc, char **argv)
26. {
27.         progName = *argv;
28.         targv = argv+1;
29.         arglim = argv+argc;
30.         yylex();
31. }
33. static unsigned offset = 0;
35. int
36. input(void)
37. {
38.         char c;
40.         if (targv >= arglim)
41.                 return(0);        /* EOF */
42.         /* end of argument, move to the next */
43.         if ((c = targv[0][offset++]) != '\0')
44.                 return(c);
45.         targv++;
46.         offset = 0;
47.         return(' ');
48. }
50. /* simple unput only backs up, doesn't allow you to */
51. /* put back different text */
52. void
53. unput(int ch)
54. {
55.         /* AT&T lex sometimes puts back the EOF ! */
56.         if(ch == 0)
57.                 return;        /* ignore, can't put back EOF */
58.         if (offset) {        /* back up in current arg */
59.                 offset--;
60.                 return;
61.         }
63.         targv--;        /* back to previous arg */
64.         offset = strlen(*targv);
65. }

复制代码

$ flex ch2-05.l  

Lichuang@LICHUANG /e/source/lex&&yacc
$ gcc lex.yy.c  -lfl
lex.yy.c:514: warning: static declaration of 'input' follows non-static declaration
ch2-05.l:4: warning: previous declaration of 'input' was here
ch2-05.l:37: error: redefinition of 'input'
lex.yy.c:1096: error: previous definition of 'input' was here

环境是MSYS下的flex.
难道是lex和flex的有兼容问题?

Answer 1

用lex ch2-05.l
或者flex -l ch2-05.l
试下

Answer 2

还是不行:

Lichuang@LICHUANG /e/source/lex&&yacc
$ flex -l ch2-05.l  

Lichuang@LICHUANG /e/source/lex&&yacc
$ gcc lex.yy.c  -lfl
lex.yy.c:559: warning: static declaration of 'input' follows non-static declaration
ch2-05.l:4: warning: previous declaration of 'input' was here
ch2-05.l:37: error: redefinition of 'input'
lex.yy.c:1128: error: previous definition of 'input' was here

Lichuang@LICHUANG /e/source/lex&&yacc
$

Answer 3

最前面加两句

2. %{
3. #define YY_NO_INPUT
4. #define YY_NO_UNPUT
5. #undef input
6. #undef unput
7. int input(void);
8. void unput(int ch);
9. unsigned verbose;
10. char *progName;
12. %}

复制代码

Answer 4

感谢,这次可以编译过去了,我找找lex的说明,回头在这里给一个解释.

Answer 5

版主怎么想到这种解决方案?因为
#ifndef YY_NO_INPUT
#ifdef __cplusplus
static int yyinput YY_PROTO(( void ));
#else
static int input YY_PROTO(( void ));
#endif
#endif
吗?添加之后是可以正常编译,但为什么可以这样处理?难道lex生成的c中这些代码是冗余的?

Answer 6

呵呵,确实是因为这段代码

Answer 7

这么快就回复了, 不过你没完全回答我的问题啊-_-#
btw, 你的头像是名子组成的?!

Answer 8

呵呵,你的观察力让我佩服.
那里有一堆宏,让你可以定制,不能说冗余的

Answer 9

^^过奖~
多谢指教