byacc/j 和 jflex 中的错误恢复使用 yacc 中的错误标记

Question

i am writing a compiler for a small language using byacc/j and jflex. i have no problem in finding first error in a given input file. the problem is i cant find more errors. first i used to use yacc and lex and i used special symbol 'error' token at the end of some grammar rules which was built in yacc and i could use 'yyerrok' to simply continue parsing and finding more errors but, in byacc/ji cant find something like that and yyerrok does not work and byacc/j does not recognize that. any suggestions to find more than one error in byacc/j? or is there ' error ' and 'yyerrok' in byacc/j?

Answer 1

The only thing that yyerrok does is reset the count of tokens since the last error notification. Yacc parsers suppress error messages in the first three tokens after an error recovery, to prevent cascading error messages.

Using yyerrok -- or setting yyerrflag to 0 -- indicates that error recovery was successful and that error messages should now be produced. It does not have any other effect: with or without yyerrok , parsing will continue.

yyerrok is a C macro, and Java doesn't have macros. So apparently it was dropped from the Java interface. But yyerrflag exists as a parser class member and you should be able to just set it to zero in a parser action.