xref: /aosp_15_r20/external/antlr/runtime/Python3/tests/t033backtracking.g (revision 16467b971bd3e2009fad32dd79016f2c7e421deb)

grammar t033backtracking;
options {
    language=Python3;
    backtrack=true;
    memoize=true;
    k=2;
}

scope Symbols {
	types;
}

@members {
    def isTypeName(self, name):
        for scope in reversed(self.Symbols_stack):
            if name in scope.types:
                return True

        return False

}

translation_unit
scope Symbols; // entire file is a scope
@init {
  $Symbols::types = set()
}
	: external_declaration+
	;

/** Either a function definition or any other kind of C decl/def.
 *  The LL(*) analysis algorithm fails to deal with this due to
 *  recursion in the declarator rules.  I'm putting in a
 *  manual predicate here so that we don't backtrack over
 *  the entire function.  Further, you get a better error
 *  as errors within the function itself don't make it fail
 *  to predict that it's a function.  Weird errors previously.
 *  Remember: the goal is to avoid backtrack like the plague
 *  because it makes debugging, actions, and errors harder.
 *
 *  Note that k=1 results in a much smaller predictor for the
 *  fixed lookahead; k=2 made a few extra thousand lines. ;)
 *  I'll have to optimize that in the future.
 */
external_declaration
options {k=1;}
	: ( declaration_specifiers? declarator declaration* '{' )=> function_definition
	| declaration
	;

function_definition
scope Symbols; // put parameters and locals into same scope for now
@init {
  $Symbols::types = set()
}
	:	declaration_specifiers? declarator
// 		(	declaration+ compound_statement	// K&R style
// 		|	compound_statement				// ANSI style
// 		)
	;

declaration
scope {
  isTypedef;
}
@init {
  $declaration::isTypedef = False
}
	: 'typedef' declaration_specifiers? {$declaration::isTypedef = True}
	  init_declarator_list ';' // special case, looking for typedef
	| declaration_specifiers init_declarator_list? ';'
	;

declaration_specifiers
	:   (   storage_class_specifier
		|   type_specifier
        |   type_qualifier
        )+
	;

init_declarator_list
	: init_declarator (',' init_declarator)*
	;

init_declarator
	: declarator //('=' initializer)?
	;

storage_class_specifier
	: 'extern'
	| 'static'
	| 'auto'
	| 'register'
	;

type_specifier
	: 'void'
	| 'char'
	| 'short'
	| 'int'
	| 'long'
	| 'float'
	| 'double'
	| 'signed'
	| 'unsigned'
// 	| struct_or_union_specifier
// 	| enum_specifier
	| type_id
	;

type_id
    :   {self.isTypeName(self.input.LT(1).getText())}? IDENTIFIER
//    	{System.out.println($IDENTIFIER.text+" is a type");}
    ;

// struct_or_union_specifier
// options {k=3;}
// scope Symbols; // structs are scopes
// @init {
//   $Symbols::types = set()
// }
// 	: struct_or_union IDENTIFIER? '{' struct_declaration_list '}'
// 	| struct_or_union IDENTIFIER
// 	;

// struct_or_union
// 	: 'struct'
// 	| 'union'
// 	;

// struct_declaration_list
// 	: struct_declaration+
// 	;

// struct_declaration
// 	: specifier_qualifier_list struct_declarator_list ';'
// 	;

// specifier_qualifier_list
// 	: ( type_qualifier | type_specifier )+
// 	;

// struct_declarator_list
// 	: struct_declarator (',' struct_declarator)*
// 	;

// struct_declarator
// 	: declarator (':' constant_expression)?
// 	| ':' constant_expression
// 	;

// enum_specifier
// options {k=3;}
// 	: 'enum' '{' enumerator_list '}'
// 	| 'enum' IDENTIFIER '{' enumerator_list '}'
// 	| 'enum' IDENTIFIER
// 	;

// enumerator_list
// 	: enumerator (',' enumerator)*
// 	;

// enumerator
// 	: IDENTIFIER ('=' constant_expression)?
// 	;

type_qualifier
	: 'const'
	| 'volatile'
	;

declarator
	: pointer? direct_declarator
	| pointer
	;

direct_declarator
	:   (	IDENTIFIER
			{
			if $declaration and $declaration::isTypedef:
				$Symbols::types.add($IDENTIFIER.text)
				print("define type "+$IDENTIFIER.text)
			}
		|	'(' declarator ')'
		)
        declarator_suffix*
	;

declarator_suffix
	:   /*'[' constant_expression ']'
    |*/   '[' ']'
//     |   '(' parameter_type_list ')'
//     |   '(' identifier_list ')'
    |   '(' ')'
	;

pointer
	: '*' type_qualifier+ pointer?
	| '*' pointer
	| '*'
	;

// parameter_type_list
// 	: parameter_list (',' '...')?
// 	;

// parameter_list
// 	: parameter_declaration (',' parameter_declaration)*
// 	;

// parameter_declaration
// 	: declaration_specifiers (declarator|abstract_declarator)*
// 	;

// identifier_list
// 	: IDENTIFIER (',' IDENTIFIER)*
// 	;

// type_name
// 	: specifier_qualifier_list abstract_declarator?
// 	;

// abstract_declarator
// 	: pointer direct_abstract_declarator?
// 	| direct_abstract_declarator
// 	;

// direct_abstract_declarator
// 	:	( '(' abstract_declarator ')' | abstract_declarator_suffix ) abstract_declarator_suffix*
// 	;

// abstract_declarator_suffix
// 	:	'[' ']'
// 	|	'[' constant_expression ']'
// 	|	'(' ')'
// 	|	'(' parameter_type_list ')'
// 	;

// initializer
// 	: assignment_expression
// 	| '{' initializer_list ','? '}'
// 	;

// initializer_list
// 	: initializer (',' initializer)*
// 	;

// // E x p r e s s i o n s

// argument_expression_list
// 	:   assignment_expression (',' assignment_expression)*
// 	;

// additive_expression
// 	: (multiplicative_expression) ('+' multiplicative_expression | '-' multiplicative_expression)*
// 	;

// multiplicative_expression
// 	: (cast_expression) ('*' cast_expression | '/' cast_expression | '%' cast_expression)*
// 	;

// cast_expression
// 	: '(' type_name ')' cast_expression
// 	| unary_expression
// 	;

// unary_expression
// 	: postfix_expression
// 	| '++' unary_expression
// 	| '--' unary_expression
// 	| unary_operator cast_expression
// 	| 'sizeof' unary_expression
// 	| 'sizeof' '(' type_name ')'
// 	;

// postfix_expression
// 	:   primary_expression
//         (   '[' expression ']'
//         |   '(' ')'
//         |   '(' argument_expression_list ')'
//         |   '.' IDENTIFIER
//         |   '*' IDENTIFIER
//         |   '->' IDENTIFIER
//         |   '++'
//         |   '--'
//         )*
// 	;

// unary_operator
// 	: '&'
// 	| '*'
// 	| '+'
// 	| '-'
// 	| '~'
// 	| '!'
// 	;

// primary_expression
// 	: IDENTIFIER
// 	| constant
// 	| '(' expression ')'
// 	;

// constant
//     :   HEX_LITERAL
//     |   OCTAL_LITERAL
//     |   DECIMAL_LITERAL
//     |	CHARACTER_LITERAL
// 	|	STRING_LITERAL
//     |   FLOATING_POINT_LITERAL
//     ;

// /////

// expression
// 	: assignment_expression (',' assignment_expression)*
// 	;

// constant_expression
// 	: conditional_expression
// 	;

// assignment_expression
// 	: lvalue assignment_operator assignment_expression
// 	| conditional_expression
// 	;

// lvalue
// 	:	unary_expression
// 	;

// assignment_operator
// 	: '='
// 	| '*='
// 	| '/='
// 	| '%='
// 	| '+='
// 	| '-='
// 	| '<<='
// 	| '>>='
// 	| '&='
// 	| '^='
// 	| '|='
// 	;

// conditional_expression
// 	: logical_or_expression ('?' expression ':' conditional_expression)?
// 	;

// logical_or_expression
// 	: logical_and_expression ('||' logical_and_expression)*
// 	;

// logical_and_expression
// 	: inclusive_or_expression ('&&' inclusive_or_expression)*
// 	;

// inclusive_or_expression
// 	: exclusive_or_expression ('|' exclusive_or_expression)*
// 	;

// exclusive_or_expression
// 	: and_expression ('^' and_expression)*
// 	;

// and_expression
// 	: equality_expression ('&' equality_expression)*
// 	;
// equality_expression
// 	: relational_expression (('=='|'!=') relational_expression)*
// 	;

// relational_expression
// 	: shift_expression (('<'|'>'|'<='|'>=') shift_expression)*
// 	;

// shift_expression
// 	: additive_expression (('<<'|'>>') additive_expression)*
// 	;

// // S t a t e m e n t s

// statement
// 	: labeled_statement
// 	| compound_statement
// 	| expression_statement
// 	| selection_statement
// 	| iteration_statement
// 	| jump_statement
// 	;

// labeled_statement
// 	: IDENTIFIER ':' statement
// 	| 'case' constant_expression ':' statement
// 	| 'default' ':' statement
// 	;

// compound_statement
// scope Symbols; // blocks have a scope of symbols
// @init {
//   $Symbols::types = {}
// }
// 	: '{' declaration* statement_list? '}'
// 	;

// statement_list
// 	: statement+
// 	;

// expression_statement
// 	: ';'
// 	| expression ';'
// 	;

// selection_statement
// 	: 'if' '(' expression ')' statement (options {k=1; backtrack=false;}:'else' statement)?
// 	| 'switch' '(' expression ')' statement
// 	;

// iteration_statement
// 	: 'while' '(' expression ')' statement
// 	| 'do' statement 'while' '(' expression ')' ';'
// 	| 'for' '(' expression_statement expression_statement expression? ')' statement
// 	;

// jump_statement
// 	: 'goto' IDENTIFIER ';'
// 	| 'continue' ';'
// 	| 'break' ';'
// 	| 'return' ';'
// 	| 'return' expression ';'
// 	;

IDENTIFIER
	:	LETTER (LETTER|'0'..'9')*
	;

fragment
LETTER
	:	'$'
	|	'A'..'Z'
	|	'a'..'z'
	|	'_'
	;

CHARACTER_LITERAL
    :   '\'' ( EscapeSequence | ~('\''|'\\') ) '\''
    ;

STRING_LITERAL
    :  '"' ( EscapeSequence | ~('\\'|'"') )* '"'
    ;

HEX_LITERAL : '0' ('x'|'X') HexDigit+ IntegerTypeSuffix? ;

DECIMAL_LITERAL : ('0' | '1'..'9' '0'..'9'*) IntegerTypeSuffix? ;

OCTAL_LITERAL : '0' ('0'..'7')+ IntegerTypeSuffix? ;

fragment
HexDigit : ('0'..'9'|'a'..'f'|'A'..'F') ;

fragment
IntegerTypeSuffix
	:	('u'|'U')? ('l'|'L')
	|	('u'|'U')  ('l'|'L')?
	;

FLOATING_POINT_LITERAL
    :   ('0'..'9')+ '.' ('0'..'9')* Exponent? FloatTypeSuffix?
    |   '.' ('0'..'9')+ Exponent? FloatTypeSuffix?
    |   ('0'..'9')+ Exponent FloatTypeSuffix?
    |   ('0'..'9')+ Exponent? FloatTypeSuffix
	;

fragment
Exponent : ('e'|'E') ('+'|'-')? ('0'..'9')+ ;

fragment
FloatTypeSuffix : ('f'|'F'|'d'|'D') ;

fragment
EscapeSequence
    :   '\\' ('b'|'t'|'n'|'f'|'r'|'\"'|'\''|'\\')
    |   OctalEscape
    ;

fragment
OctalEscape
    :   '\\' ('0'..'3') ('0'..'7') ('0'..'7')
    |   '\\' ('0'..'7') ('0'..'7')
    |   '\\' ('0'..'7')
    ;

fragment
UnicodeEscape
    :   '\\' 'u' HexDigit HexDigit HexDigit HexDigit
    ;

WS  :  (' '|'\r'|'\t'|'\u000C'|'\n') {$channel=HIDDEN;}
    ;

COMMENT
    :   '/*' ( options {greedy=false;} : . )* '*/' {$channel=HIDDEN;}
    ;

LINE_COMMENT
    : '//' ~('\n'|'\r')* '\r'? '\n' {$channel=HIDDEN;}
    ;

// ignore #line info for now
LINE_COMMAND
    : '#' ~('\n'|'\r')* '\r'? '\n' {$channel=HIDDEN;}
    ;