/* $NetBSD: btyacc_demo.y,v 1.1.1.3 2016/01/09 21:59:45 christos Exp $ */ /* * 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 #include %} %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 %token CONSTANT %token EXTERN REGISTER STATIC CONST VOLATILE IF THEN ELSE CLCL %type expr() %type decl() declarator_list(, ) decl_list() %type statement() statement_list() block_statement() %type declarator(, ) formal_arg() %type decl_specs() decl_spec() typename() cv_quals cv_qual %type opt_scope() %type formal_arg_list() nonempty_formal_arg_list() %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($$->scope); free($$->type); } decl %destructor { printf("%s accessed by symbol with type (case s.b. 279 & 280) @ position[%d,%d..%d,%d]\n", msg, @$.first_line, @$.first_column, @$.last_line, @$.last_column); free($$); } %destructor { printf("%s accessed by symbol of any type other than @ position[%d,%d..%d,%d]\n", msg, @$.first_line, @$.first_column, @$.last_line, @$.last_column); free($$); } <*> %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);