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/*
* demonstrate enhancements derived from btyacc:
* backtracking to resolve conflicts
* semantic disambiguation via []-actions invoking YYVALID & YYERROR
* %locations
* @$ & @N to refer to lhs & rhs symbol location
* %destructor
* syntactic suger for inherited attributes
* extension to %type to define inherited attribute type
*/
%LOCATIONS
%{
/* dummy types just for compile check */
typedef int Code;
typedef int Decl_List;
typedef int Expr;
typedef int Expr_List;
typedef int Scope;
typedef int Type;
enum Operator { ADD, SUB, MUL, MOD, DIV, DEREF };
typedef unsigned char bool;
typedef struct Decl {
Scope *scope;
Type *type;
bool (*istype)(void);
} Decl;
#include "btyacc_demo.tab.h"
#include <stdlib.h>
#include <stdio.h>
%}
%union {
Scope *scope;
Expr *expr;
Expr_List *elist;
Type *type;
Decl *decl;
Decl_List *dlist;
Code *code;
char *id;
};
%left '+' '-'
%left '*' '/' '%'
%nonassoc PREFIX
%nonassoc POSTFIX '(' '[' '.'
%token <id> ID
%token <expr> CONSTANT
%token EXTERN REGISTER STATIC CONST VOLATILE IF THEN ELSE CLCL
%type <expr> expr(<scope>)
%type decl(<scope>) declarator_list(<scope>, <type>)
decl_list(<scope>)
%type <code> statement(<scope>) statement_list(<scope>)
block_statement(<scope>)
%type <decl> declarator(<scope>, <type>) formal_arg(<scope>)
%type <type> decl_specs(<scope>) decl_spec(<scope>) typename(<scope>)
cv_quals cv_qual
%type <scope> opt_scope(<scope>)
%type <dlist> formal_arg_list(<scope>) nonempty_formal_arg_list(<scope>)
%destructor { // 'msg' is a 'char *' indicating the context of destructor invocation
printf("%s accessed by symbol \"decl\" (case s.b. 273) @ position[%d,%d..%d,%d]\n",
msg,
@$.first_line, @$.first_column,
@$.last_line, @$.last_column);
free($<decl>$->scope); free($<decl>$->type); } decl
%destructor { printf("%s accessed by symbol with type <decl> (case s.b. 279 & 280) @ position[%d,%d..%d,%d]\n",
msg,
@$.first_line, @$.first_column,
@$.last_line, @$.last_column);
free($$); } <decl>
%destructor { printf("%s accessed by symbol of any type other than <decl> @ position[%d,%d..%d,%d]\n",
msg,
@$.first_line, @$.first_column,
@$.last_line, @$.last_column);
free($$); } <*>
%destructor { printf("%s accessed by symbol with no type @ position[%d,%d..%d,%d]\n",
msg,
@$.first_line, @$.first_column,
@$.last_line, @$.last_column);
/* in this example, we don't know what to do here */ } <>
%start input
%%
opt_scope($e): [ $$ = $e; ]
| CLCL [ $$ = global_scope; ]
| opt_scope ID CLCL [ Decl *d = lookup($1, $2);
if (!d || !d->scope) YYERROR;
$$ = d->scope; ]
;
typename($e): opt_scope ID
[ Decl *d = lookup($1, $2);
if (d == NULL || d->istype() == 0) YYERROR;
$$ = d->type; ]
;
input: decl_list(global_scope = new_scope(0)) ;
decl_list($e): | decl_list decl($e) ;
decl($e):
decl_specs declarator_list($e,$1) ';' [YYVALID;]
| decl_specs declarator($e,$1) block_statement(start_fn_def($e, $2))
{ /* demonstrate use of @$ & @N, although this is just the
default computation and so is not necessary */
@$.first_line = @1.first_line;
@$.first_column = @1.first_column;
@$.last_line = @3.last_line;
@$.last_column = @3.last_column;
finish_fn_def($2, $3); }
;
decl_specs($e):
decl_spec [ $$ = $1; ]
| decl_specs decl_spec($e) [ $$ = type_combine($1, $2); ]
;
cv_quals: [ $$ = 0; ]
| cv_quals cv_qual [ $$ = type_combine($1, $2); ]
;
decl_spec($e):
cv_qual [ $$ = $1; ]
| typename [ $$ = $1; ]
| EXTERN [ $$ = bare_extern(); ]
| REGISTER [ $$ = bare_register(); ]
| STATIC [ $$ = bare_static(); ]
;
cv_qual:
CONST [ $$ = bare_const(); ]
| VOLATILE [ $$ = bare_volatile(); ]
;
declarator_list($e, $t):
declarator_list ',' declarator($e, $t)
| declarator
;
declarator($e, $t):
/* empty */ [ if (!$t) YYERROR; ]
{ $$ = declare($e, 0, $t); }
| ID { $$ = declare($e, $1, $t); }
| '(' declarator($e, $t) ')' { $$ = $2; }
| '*' cv_quals declarator($e, $t) %prec PREFIX
{ $$ = make_pointer($3, $2); }
| declarator '[' expr($e) ']'
{ $$ = make_array($1->type, $3); }
| declarator '(' formal_arg_list($e) ')' cv_quals
{ $$ = build_function($1, $3, $5); }
;
formal_arg_list($e): { $$ = 0; }
| nonempty_formal_arg_list { $$ = $1; }
;
nonempty_formal_arg_list($e):
nonempty_formal_arg_list ',' formal_arg($e) { $$ = append_dlist($1, $3); }
| formal_arg { $$ = build_dlist($1); }
;
formal_arg($e):
decl_specs declarator($e,$1) { $$ = $2; }
;
expr($e):
expr '+' expr($e) { $$ = build_expr($1, ADD, $3); }
| expr '-' expr($e) { $$ = build_expr($1, SUB, $3); }
| expr '*' expr($e) { $$ = build_expr($1, MUL, $3); }
| expr '%' expr($e) { $$ = build_expr($1, MOD, $3); }
| expr '/' expr($e) { $$ = build_expr($1, DIV, $3); }
| '*' expr($e) %prec PREFIX { $$ = build_expr(0, DEREF, $2); }
| ID { $$ = var_expr($e, $1); }
| CONSTANT { $$ = $1; }
;
statement($e):
decl { $$ = 0; }
| expr($e) ';' [YYVALID;] { $$ = build_expr_code($1); }
| IF '(' expr($e) ')' THEN statement($e) ELSE statement($e) [YYVALID;]
{ $$ = build_if($3, $6, $8); }
| IF '(' expr($e) ')' THEN statement($e) [YYVALID;]
{ $$ = build_if($3, $6, 0); }
| block_statement(new_scope($e)) [YYVALID;]{ $$ = $1; }
;
statement_list($e): { $$ = 0; }
| statement_list statement($e) { $$ = code_append($1, $2); }
;
block_statement($e):
'{' statement_list($e) '}' { $$ = $2; }
;
%%
extern int YYLEX_DECL();
extern void YYERROR_DECL();
extern Scope *global_scope;
extern Decl * lookup(Scope *scope, char *id);
extern Scope * new_scope(Scope *outer_scope);
extern Scope * start_fn_def(Scope *scope, Decl *fn_decl);
extern void finish_fn_def(Decl *fn_decl, Code *block);
extern Type * type_combine(Type *specs, Type *spec);
extern Type * bare_extern(void);
extern Type * bare_register(void);
extern Type * bare_static(void);
extern Type * bare_const(void);
extern Type * bare_volatile(void);
extern Decl * declare(Scope *scope, char *id, Type *type);
extern Decl * make_pointer(Decl *decl, Type *type);
extern Decl * make_array(Type *type, Expr *expr);
extern Decl * build_function(Decl *decl, Decl_List *dlist, Type *type);
extern Decl_List * append_dlist(Decl_List *dlist, Decl *decl);
extern Decl_List * build_dlist(Decl *decl);
extern Expr * build_expr(Expr *left, enum Operator op, Expr *right);
extern Expr * var_expr(Scope *scope, char *id);
extern Code * build_expr_code(Expr *expr);
extern Code * build_if(Expr *cond_expr, Code *then_stmt, Code *else_stmt);
extern Code * code_append(Code *stmt_list, Code *stmt);
|
