使用Lex和Yacc开发C语言的编译器

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(1) 从网站：http://www.lysator.liu.se/c/ 下载C语言的语法文件：
The ANSI C grammar (Yacc and Lex)
(2) 编译词法文件：

> lex c.l

(3) 编译语法文件：

> yacc -dv c.y

说明：-d：产生头文件y.yab.h，-v：产生分析表y.output。针对else产生的移进规约冲突，采用了yacc的默认动作“移进”解决。
(4) 编译语法分析器：

> cc lex.yy.c y.tab.c -ll

(5) 测试：
编写测试程序test.c

#include "stdio.h"

int main(){

int a = 0;

for(; a < 10; a++){

printf("hello from sun! ");

}

运行：

> ./a.out < test.c

结果如下：

"stdio.h"

int (){

int = ;

for(; < ; ++){

int("hello from sun hong hao! ");

}

发现c.y文件中没有语义动作。只是进行了词法扫描一下，所以得到结果就是上面的样子了。

(5) 贴一下y.out里的规则：

0 $accept : translation_unit $end

1 primary_expression : IDENTIFIER

2 | CONSTANT

3 | STRING_LITERAL

4 | '(' expression ')'

5 postfix_expression : primary_expression

6 | postfix_expression '[' expression ']'

7 | postfix_expression '(' ')'

8 | postfix_expression '(' argument_expression_list ')'

9 | postfix_expression '.' IDENTIFIER

10 | postfix_expression PTR_OP IDENTIFIER

11 | postfix_expression INC_OP

12 | postfix_expression DEC_OP

13 argument_expression_list : assignment_expression

14 | argument_expression_list ',' assignment_expression

15 unary_expression : postfix_expression

16 | INC_OP unary_expression

17 | DEC_OP unary_expression

18 | unary_operator cast_expression

19 | SIZEOF unary_expression

20 | SIZEOF '(' type_name ')'

21 unary_operator : '&'

22 | '*'

23 | '+'

24 | '-'

25 | '~'

26 | '!'

27 cast_expression : unary_expression

28 | '(' type_name ')' cast_expression

29 multiplicative_expression : cast_expression

30 | multiplicative_expression '*' cast_expression

31 | multiplicative_expression '/' cast_expression

32 | multiplicative_expression '%' cast_expression

33 additive_expression : multiplicative_expression

34 | additive_expression '+' multiplicative_expression

35 | additive_expression '-' multiplicative_expression

36 shift_expression : additive_expression

37 | shift_expression LEFT_OP additive_expression

38 | shift_expression RIGHT_OP additive_expression

39 relational_expression : shift_expression

40 | relational_expression '<' shift_expression

41 | relational_expression '>' shift_expression

42 | relational_expression LE_OP shift_expression

43 | relational_expression GE_OP shift_expression

44 equality_expression : relational_expression

45 | equality_expression EQ_OP relational_expression

46 | equality_expression NE_OP relational_expression

47 and_expression : equality_expression

48 | and_expression '&' equality_expression

49 exclusive_or_expression : and_expression

50 | exclusive_or_expression '^' and_expression

51 inclusive_or_expression : exclusive_or_expression

52 | inclusive_or_expression '|' exclusive_or_expression

53 logical_and_expression : inclusive_or_expression

54 | logical_and_expression AND_OP inclusive_or_expression

55 logical_or_expression : logical_and_expression

56 | logical_or_expression OR_OP logical_and_expression

57 conditional_expression : logical_or_expression

58 | logical_or_expression '?' expression ':' conditional_expression

59 assignment_expression : conditional_expression

60 | unary_expression assignment_operator assignment_expression

61 assignment_operator : '='

62 | MUL_ASSIGN

63 | DIV_ASSIGN

64 | MOD_ASSIGN

65 | ADD_ASSIGN

66 | SUB_ASSIGN

67 | LEFT_ASSIGN

68 | RIGHT_ASSIGN

69 | AND_ASSIGN

70 | XOR_ASSIGN

71 | OR_ASSIGN

72 expression : assignment_expression

73 | expression ',' assignment_expression

74 constant_expression : conditional_expression

75 declaration : declaration_specifiers ';'

76 | declaration_specifiers init_declarator_list ';'

77 declaration_specifiers : storage_class_specifier

78 | storage_class_specifier declaration_specifiers

79 | type_specifier

80 | type_specifier declaration_specifiers

81 | type_qualifier

82 | type_qualifier declaration_specifiers

83 init_declarator_list : init_declarator

84 | init_declarator_list ',' init_declarator

85 init_declarator : declarator

86 | declarator '=' initializer

87 storage_class_specifier : TYPEDEF

88 | EXTERN

89 | STATIC

90 | AUTO

91 | REGISTER

92 type_specifier : VOID

93 | CHAR

94 | SHORT

95 | INT

96 | LONG

97 | FLOAT

98 | DOUBLE

99 | SIGNED

100 | UNSIGNED

101 | struct_or_union_specifier

102 | enum_specifier

103 | TYPE_NAME

104 struct_or_union_specifier : struct_or_union IDENTIFIER '{' struct_declaration_list '}'

105 | struct_or_union '{' struct_declaration_list '}'

106 | struct_or_union IDENTIFIER

107 struct_or_union : STRUCT

108 | UNION

109 struct_declaration_list : struct_declaration

110 | struct_declaration_list struct_declaration

111 struct_declaration : specifier_qualifier_list struct_declarator_list ';'

112 specifier_qualifier_list : type_specifier specifier_qualifier_list

113 | type_specifier

114 | type_qualifier specifier_qualifier_list

115 | type_qualifier

116 struct_declarator_list : struct_declarator

117 | struct_declarator_list ',' struct_declarator

118 struct_declarator : declarator

119 | ':' constant_expression

120 | declarator ':' constant_expression

121 enum_specifier : ENUM '{' enumerator_list '}'

122 | ENUM IDENTIFIER '{' enumerator_list '}'

123 | ENUM IDENTIFIER

124 enumerator_list : enumerator

125 | enumerator_list ',' enumerator

126 enumerator : IDENTIFIER

127 | IDENTIFIER '=' constant_expression

128 type_qualifier : CONST

129 | VOLATILE

130 declarator : pointer direct_declarator

131 | direct_declarator

132 direct_declarator : IDENTIFIER

133 | '(' declarator ')'

134 | direct_declarator '[' constant_expression ']'

135 | direct_declarator '[' ']'

136 | direct_declarator '(' parameter_type_list ')'

137 | direct_declarator '(' identifier_list ')'

138 | direct_declarator '(' ')'

139 pointer : '*'

140 | '*' type_qualifier_list

141 | '*' pointer

142 | '*' type_qualifier_list pointer

143 type_qualifier_list : type_qualifier

144 | type_qualifier_list type_qualifier

145 parameter_type_list : parameter_list

146 | parameter_list ',' ELLIPSIS

147 parameter_list : parameter_declaration

148 | parameter_list ',' parameter_declaration

149 parameter_declaration : declaration_specifiers declarator

150 | declaration_specifiers abstract_declarator

151 | declaration_specifiers

152 identifier_list : IDENTIFIER

153 | identifier_list ',' IDENTIFIER

154 type_name : specifier_qualifier_list

155 | specifier_qualifier_list abstract_declarator

156 abstract_declarator : pointer

157 | direct_abstract_declarator

158 | pointer direct_abstract_declarator

159 direct_abstract_declarator : '(' abstract_declarator ')'

160 | '[' ']'

161 | '[' constant_expression ']'

162 | direct_abstract_declarator '[' ']'

163 | direct_abstract_declarator '[' constant_expression ']'

164 | '(' ')'

165 | '(' parameter_type_list ')'

166 | direct_abstract_declarator '(' ')'

167 | direct_abstract_declarator '(' parameter_type_list ')'

168 initializer : assignment_expression

169 | '{' initializer_list '}'

170 | '{' initializer_list ',' '}'

171 initializer_list : initializer

172 | initializer_list ',' initializer

173 statement : labeled_statement

174 | compound_statement

175 | expression_statement

176 | selection_statement

177 | iteration_statement

178 | jump_statement

179 labeled_statement : IDENTIFIER ':' statement

180 | CASE constant_expression ':' statement

181 | DEFAULT ':' statement

182 compound_statement : '{' '}'

183 | '{' statement_list '}'

184 | '{' declaration_list '}'

185 | '{' declaration_list statement_list '}'

186 declaration_list : declaration

187 | declaration_list declaration

188 statement_list : statement

189 | statement_list statement

190 expression_statement : ';'

191 | expression ';'

192 selection_statement : IF '(' expression ')' statement

193 | IF '(' expression ')' statement ELSE statement

194 | SWITCH '(' expression ')' statement

195 iteration_statement : WHILE '(' expression ')' statement

196 | DO statement WHILE '(' expression ')' ';'

197 | FOR '(' expression_statement expression_statement ')' statement

198 | FOR '(' expression_statement expression_statement expression ')' statement

199 jump_statement : GOTO IDENTIFIER ';'

200 | CONTINUE ';'

201 | BREAK ';'

202 | RETURN ';'

203 | RETURN expression ';'

204 translation_unit : external_declaration

205 | translation_unit external_declaration

206 external_declaration : function_definition

207 | declaration

208 function_definition : declaration_specifiers declarator declaration_list compound_statement

209 | declaration_specifiers declarator compound_statement

210 | declarator declaration_list compound_statement

211 | declarator compound_statement

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