1 /* $NetBSD: btyacc_demo.y,v 1.1.1.3 2016/01/09 21:59:45 christos Exp $ */
2
3 /*
4 * demonstrate enhancements derived from btyacc:
5 * backtracking to resolve conflicts
6 * semantic disambiguation via []-actions invoking YYVALID & YYERROR
7 * %locations
8 * @$ & @N to refer to lhs & rhs symbol location
9 * %destructor
10 * syntactic suger for inherited attributes
11 * extension to %type to define inherited attribute type
12 */
13
14 %LOCATIONS
15
16 %{
17 /* dummy types just for compile check */
18 typedef int Code;
19 typedef int Decl_List;
20 typedef int Expr;
21 typedef int Expr_List;
22 typedef int Scope;
23 typedef int Type;
24 enum Operator { ADD, SUB, MUL, MOD, DIV, DEREF };
25
26 typedef unsigned char bool;
27 typedef struct Decl {
28 Scope *scope;
29 Type *type;
30 bool (*istype)(void);
31 } Decl;
32
33 #include "btyacc_demo.tab.h"
34 #include <stdlib.h>
35 #include <stdio.h>
36 %}
37
38 %union {
39 Scope *scope;
40 Expr *expr;
41 Expr_List *elist;
42 Type *type;
43 Decl *decl;
44 Decl_List *dlist;
45 Code *code;
46 char *id;
47 };
48
49 %left '+' '-'
50 %left '*' '/' '%'
51 %nonassoc PREFIX
52 %nonassoc POSTFIX '(' '[' '.'
53
54 %token <id> ID
55 %token <expr> CONSTANT
56 %token EXTERN REGISTER STATIC CONST VOLATILE IF THEN ELSE CLCL
57
58 %type <expr> expr(<scope>)
59 %type decl(<scope>) declarator_list(<scope>, <type>)
60 decl_list(<scope>)
61 %type <code> statement(<scope>) statement_list(<scope>)
62 block_statement(<scope>)
63 %type <decl> declarator(<scope>, <type>) formal_arg(<scope>)
64 %type <type> decl_specs(<scope>) decl_spec(<scope>) typename(<scope>)
65 cv_quals cv_qual
66 %type <scope> opt_scope(<scope>)
67 %type <dlist> formal_arg_list(<scope>) nonempty_formal_arg_list(<scope>)
68
69 %destructor { // 'msg' is a 'char *' indicating the context of destructor invocation
70 printf("%s accessed by symbol \"decl\" (case s.b. 273) @ position[%d,%d..%d,%d]\n",
71 msg,
72 @$.first_line, @$.first_column,
73 @$.last_line, @$.last_column);
74 free($<decl>$->scope); free($<decl>$->type); } decl
75 %destructor { printf("%s accessed by symbol with type <decl> (case s.b. 279 & 280) @ position[%d,%d..%d,%d]\n",
76 msg,
77 @$.first_line, @$.first_column,
78 @$.last_line, @$.last_column);
79 free($$); } <decl>
80 %destructor { printf("%s accessed by symbol of any type other than <decl> @ position[%d,%d..%d,%d]\n",
81 msg,
82 @$.first_line, @$.first_column,
83 @$.last_line, @$.last_column);
84 free($$); } <*>
85 %destructor { printf("%s accessed by symbol with no type @ position[%d,%d..%d,%d]\n",
86 msg,
87 @$.first_line, @$.first_column,
88 @$.last_line, @$.last_column);
89 /* in this example, we don't know what to do here */ } <>
90
91 %start input
92
93 %%
94
95 opt_scope($e): [ $$ = $e; ]
96 | CLCL [ $$ = global_scope; ]
97 | opt_scope ID CLCL [ Decl *d = lookup($1, $2);
98 if (!d || !d->scope) YYERROR;
99 $$ = d->scope; ]
100 ;
101
102 typename($e): opt_scope ID
103 [ Decl *d = lookup($1, $2);
104 if (d == NULL || d->istype() == 0) YYERROR;
105 $$ = d->type; ]
106 ;
107
108 input: decl_list(global_scope = new_scope(0)) ;
109 decl_list($e): | decl_list decl($e) ;
110 decl($e):
111 decl_specs declarator_list($e,$1) ';' [YYVALID;]
112 | decl_specs declarator($e,$1) block_statement(start_fn_def($e, $2))
113 { /* demonstrate use of @$ & @N, although this is just the
114 default computation and so is not necessary */
115 @$.first_line = @1.first_line;
116 @$.first_column = @1.first_column;
117 @$.last_line = @3.last_line;
118 @$.last_column = @3.last_column;
119 finish_fn_def($2, $3); }
120 ;
121
122 decl_specs($e):
123 decl_spec [ $$ = $1; ]
124 | decl_specs decl_spec($e) [ $$ = type_combine($1, $2); ]
125 ;
126
127 cv_quals: [ $$ = 0; ]
128 | cv_quals cv_qual [ $$ = type_combine($1, $2); ]
129 ;
130
131 decl_spec($e):
132 cv_qual [ $$ = $1; ]
133 | typename [ $$ = $1; ]
134 | EXTERN [ $$ = bare_extern(); ]
135 | REGISTER [ $$ = bare_register(); ]
136 | STATIC [ $$ = bare_static(); ]
137 ;
138
139 cv_qual:
140 CONST [ $$ = bare_const(); ]
141 | VOLATILE [ $$ = bare_volatile(); ]
142 ;
143
144 declarator_list($e, $t):
145 declarator_list ',' declarator($e, $t)
146 | declarator
147 ;
148
declarator($e,$t)149 declarator($e, $t):
150 /* empty */ [ if (!$t) YYERROR; ]
151 { $$ = declare($e, 0, $t); }
152 | ID { $$ = declare($e, $1, $t); }
153 | '(' declarator($e, $t) ')' { $$ = $2; }
154 | '*' cv_quals declarator($e, $t) %prec PREFIX
155 { $$ = make_pointer($3, $2); }
156 | declarator '[' expr($e) ']'
157 { $$ = make_array($1->type, $3); }
158 | declarator '(' formal_arg_list($e) ')' cv_quals
159 { $$ = build_function($1, $3, $5); }
160 ;
161
formal_arg_list($e)162 formal_arg_list($e): { $$ = 0; }
163 | nonempty_formal_arg_list { $$ = $1; }
164 ;
165 nonempty_formal_arg_list($e):
166 nonempty_formal_arg_list ',' formal_arg($e) { $$ = append_dlist($1, $3); }
167 | formal_arg { $$ = build_dlist($1); }
168 ;
formal_arg($e)169 formal_arg($e):
170 decl_specs declarator($e,$1) { $$ = $2; }
171 ;
172
173 expr($e):
174 expr '+' expr($e) { $$ = build_expr($1, ADD, $3); }
175 | expr '-' expr($e) { $$ = build_expr($1, SUB, $3); }
176 | expr '*' expr($e) { $$ = build_expr($1, MUL, $3); }
177 | expr '%' expr($e) { $$ = build_expr($1, MOD, $3); }
178 | expr '/' expr($e) { $$ = build_expr($1, DIV, $3); }
179 | '*' expr($e) %prec PREFIX { $$ = build_expr(0, DEREF, $2); }
180 | ID { $$ = var_expr($e, $1); }
181 | CONSTANT { $$ = $1; }
182 ;
183
statement($e)184 statement($e):
185 decl { $$ = 0; }
186 | expr($e) ';' [YYVALID;] { $$ = build_expr_code($1); }
187 | IF '(' expr($e) ')' THEN statement($e) ELSE statement($e) [YYVALID;]
188 { $$ = build_if($3, $6, $8); }
189 | IF '(' expr($e) ')' THEN statement($e) [YYVALID;]
190 { $$ = build_if($3, $6, 0); }
191 | block_statement(new_scope($e)) [YYVALID;]{ $$ = $1; }
192 ;
193
statement_list($e)194 statement_list($e): { $$ = 0; }
195 | statement_list statement($e) { $$ = code_append($1, $2); }
196 ;
197
198 block_statement($e):
199 '{' statement_list($e) '}' { $$ = $2; }
200 ;
201 %%
202
203 extern int YYLEX_DECL();
204 extern void YYERROR_DECL();
205
206 extern Scope *global_scope;
207
208 extern Decl * lookup(Scope *scope, char *id);
209 extern Scope * new_scope(Scope *outer_scope);
210 extern Scope * start_fn_def(Scope *scope, Decl *fn_decl);
211 extern void finish_fn_def(Decl *fn_decl, Code *block);
212 extern Type * type_combine(Type *specs, Type *spec);
213 extern Type * bare_extern(void);
214 extern Type * bare_register(void);
215 extern Type * bare_static(void);
216 extern Type * bare_const(void);
217 extern Type * bare_volatile(void);
218 extern Decl * declare(Scope *scope, char *id, Type *type);
219 extern Decl * make_pointer(Decl *decl, Type *type);
220 extern Decl * make_array(Type *type, Expr *expr);
221 extern Decl * build_function(Decl *decl, Decl_List *dlist, Type *type);
222 extern Decl_List * append_dlist(Decl_List *dlist, Decl *decl);
223 extern Decl_List * build_dlist(Decl *decl);
224 extern Expr * build_expr(Expr *left, enum Operator op, Expr *right);
225 extern Expr * var_expr(Scope *scope, char *id);
226 extern Code * build_expr_code(Expr *expr);
227 extern Code * build_if(Expr *cond_expr, Code *then_stmt, Code *else_stmt);
228 extern Code * code_append(Code *stmt_list, Code *stmt);
229