Exception Based Syntax Error Recovery
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The nature of these messages depends on both the language definition and the compiler or interpreter. You may have noticed that across languages and implementations these messages differ greatly in their usefulness and specificity. One antlr4 error handling feature common to all of the languages you used is syntax error recovery. In
Antlr Error Listener Example
the simplest sense, syntax error recovery is the mechanism by which a compiler or interpreter continues to parse a program
Antlr Error Handling
(and find more syntax errors) after it encounters an instance of invalid syntax. Your task in this assignment is to implement syntax error recovery for the calculator language we have been developing in
Antlr4 Throw Exception On Error
class. We provide a basic scanner and parser (written in C). Given this initial code base, you must: Translate the code we provide into C++. Obviously, you must make any changes needed for the code to compile without errors under g++. In addition, you must replace any calls to C libraries (e.g. for I/O) with the standard C++ equivalents (no printf!). Extend the language with types and declarations, antlr throw exception as shown in Figure 4.11 in the book. Implement exception-based syntax error recovery, as described in Section 2.3.4 on the CD. Output a syntax tree with the structure suggested (but not completely defined) in Example 4.15 and Figure 4.12. Your output should be in linear, parenthesized form reminiscent of (but not the same as) what you generated in Assignment 1. More specifically, every parent and its children in the tree should be represented a parenthesized list, recursively. For example, the tree a / | \ b c d /| | e f g would be represented by the string (a (b e f) (c g) d). If you are familiar with Lisp or Scheme, this is the standard notation for trees in these languages. When run, your program should read a calculator program from standard input, and then output either syntax error messages or a correct syntax tree. The initial source code for this assignment is available HERE. As currently written, it prints a trace of predictions and matches. You should disable that. Suggestions You do not have to build the syntax tree as an explicit data structure in your program in order to generate the right output. You
Reporting and Recovery This document describes the error recovery features introduced in Version 0.7.1. This document also describes how features have changed since Version 0.6. The first recognitionexception antlr 4 change (from 0.6) is that we have two new exceptions: . ParseException . antlr exceptions TokenMgrError Whenever the token manager detects a problem, it throws the exception TokenMgrError. Previously, it used to print the bailerrorstrategy message: Lexical Error ... following which it use to throw the exception ParseError. Whenever the parser detects a problem, it throws the exception ParseException. Previously, it used to print the message: Encountered https://www.cs.rochester.edu/courses/454/fall2011/assignments/syntax_error_recovery.shtml ... Was expecting one of ... following which it use to throw the exception ParseError. In Version 0.7.1, error messages are never printed explicitly, rather this information is stored inside the exception objects that are thrown. Please see the classes ParseException.java and TokenMgrError.java (that get generated by JavaCC [tm] during parser generation) for more details. If the thrown exceptions are never caught, then a standard https://javacc.java.net/doc/errorrecovery.html action is taken by the virtual machine which normally includes printing the stack trace and also the result of the "toString" method in the exception. So if you do not catch the JavaCC exceptions, a message quite similar to the ones in Version 0.6. But if you catch the exception, you must print the message yourself. Exceptions in the Java [tm] programming language are all subclasses of type Throwable. Furthermore, exceptions are divided into two broad categories - ERRORS and other exceptions. Errors are exceptions that one is not expected to recover from - examples of these are ThreadDeath or OutOfMemoryError. Errors are indicated by subclassing the exception "Error". Exceptions subclassed from Error need not be specified in the "throws" clause of method declarations. Exceptions other than errors are typically defined by subclassing the exception "Exception". These exceptions are typically handled by the user program and must be declared in throws clauses of method declarations (if it is possible for the method to throw that exception). The exception TokenMgrError is a subclass of Error, while the exception ParseException is a subclass of Exception. The reasoning here is that the token manage
here for a quick overview of the site Help Center Detailed answers to any questions you might have Meta Discuss the workings and policies of this site About Us Learn more about http://stackoverflow.com/questions/30185876/handle-exception-as-a-parse-error-in-bison Stack Overflow the company Business Learn more about hiring developers or posting ads with us Stack Overflow Questions Jobs Documentation Tags Users Badges Ask Question x Dismiss Join the Stack Overflow Community Stack Overflow is a community of 4.7 million programmers, just like you, helping each other. Join them; it only takes a minute: Sign up Handle exception as a parse error in bison up vote 0 down vote favorite How error handling do i catch en exception thrown upon executing a rule in bison like foo : BAR { $$ = new Bar($1); } The Bar constructor throws std::invalid_argument exception if it's argument is inappropriate. I would like to catch that exception and raise a compilation error, so I get native error message like input:42.10: Bad value `baz' for bar Also there are a lot of this kind of rules, so It exception based syntax would be great to handle that not within rule itself, but somewhere in the parser. c++ exception-handling bison share|improve this question edited May 18 '15 at 7:07 akim 2,9321325 asked May 12 '15 at 8:44 uranix 248110 add a comment| 1 Answer 1 active oldest votes up vote 1 down vote accepted If you are using lalr1.cc, the C++ skeleton of Bison, then there is some limited support for exceptions: if you throw a yy::parser::syntax_error, then the exception is caught as a syntax error, duly reported, and the parser enters the error recovery mode. That's very much like using YYERROR. If you throw anything else, the whole parsing is aborted, the stack is cleaned, and the exception is rethrown. That's YYABORT. So if you'd like to errors caught as rule-reduction you should throw the specific exception, see C++ Parser Interface Documentation of Bison. share|improve this answer answered May 13 '15 at 7:58 akim 2,9321325 add a comment| Your Answer draft saved draft discarded Sign up or log in Sign up using Google Sign up using Facebook Sign up using Email and Password Post as a guest Name Email Post as a guest Name Email discard By posting your answer, you agree to the privacy policy and terms of s
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