t2.y

从lex&yacc说到编译器

%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>)

%start input

%%

opt_scope($e):		[ $$ = $e; ]
  | CLCL		[ $$ = global_scope; ]
  | opt_scope ID CLCL	[ Decl *d = lookup($1, $2);
			  if (!d || !d->scope) YERROR;
			  $$ = d->scope; ]
  ;

typename($e): opt_scope ID
      [ Decl *d = lookup($1, $2);
	if (!d || !d->istype()) 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))
      { 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, REF, $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; }
  ;