Home > Error Handling > Antlr Custom Error Recovery

Antlr Custom Error Recovery


i.e. do you have solution? –Berto Tuwondila Feb 22 '12 at 6:43 add a comment| 1 Answer 1 active oldest votes up vote 1 down vote I think you need to override To get ANTLR to generate lexers that pass on RecognitionException's to the parser as TokenStreamException's, use the defaultErrorHandler=false grammar option. Matching and control flow continues as if the error had not occurred. have a peek here

Other Recovery Mechanisms Within ANTLR Runtimes There is one other aspect of recovery which you may need to customize, and that is what happens when a mismatch() occurs. no longer parsing This is the current version of my grammar (work still in progress, so I still need to tidy and correct stuff, but it does work) Note! Generally, you will still call reportError(), unless you wish to suppress the error, but then you can use your own method/algorithm to recover the input point. We could of course // use a custom action instead if there were special rules about // recovery for this language - here we just don't want to drop out // his explanation

Antlr4 Error Handling

But, we want all this to happen automatically, and it would be better if we could write one resync rule that we could use (judiciously) anywhere in our grammar. ValidCfgElement ValidCfgElement ValidCfgElement InvalidToken ValidCfgElementNotParsed Report message to a moderator Re: Custom Syntax Error Recovery [message #1062158 is a reply to message #1062146] Thu, 06 June 2013 10:04 However it creates a recovery problem as it stands in that quite a large number of the possible syntax errors found within the rule classMember will cause the * loop to

  • An example of this approach is to append errors to a List within the lexer and parser and to provide a public method to allow access to the list: @members {
  • And you are right, I need to have catch and resync on other rules.
  • Thanks in advance.
  • ERROR The requested URL could not be retrieved The following error was encountered while trying to retrieve the URL: Connection to failed.

Overview Package Class Use Tree Deprecated Index Help Prev Class Next Class Frames No Frames All Classes Summary: Nested| Field| Constr| Method Detail: Field| Constr| Method org.antlr.v4.runtime Interface ANTLRErrorStrategy All Known Custom Error Reporting To change the default error reporting behavior, override either the displayRecognitionError() or the emitErrorMessage() methods in the lexer and parser. The only slight risk here is that the // block becomes MORE inclusive than it should but as the script is // in error, this is a better course than throwing Antlr Parser The key to this trick is to create a parser rule that consists only of a single empty alt (epsilon set in jargon), then use action code within the rule to

i follow this link http://www.antlr.org/blog/antlr3/error.handling.tml but i don't have that solutions. Antlr Error Listener Example Second, you may specify your own exception handlers in a variety of ways, as described later. In fact, all we need do is utilize a simple trick, which is perfectly 'legal' and will do all the calculations for us. void reportError(Parserrecognizer, RecognitionExceptione) Report any kind of RecognitionException.

This is useful * in situations where only a subset of tokens can begin a new construct * (such as the start of a new statement in a block) and we In our example rule, we clearly want to know what the First set is for the rule classMember, as when we apply our resync, this is the set of tokens that I tried something else. Why don't my users have separate desktops in Windows 10?

Antlr Error Listener Example

The error strategy implementation is responsible for calling Parser.notifyErrorListeners(java.lang.String) as appropriate. http://stackoverflow.com/questions/9388900/antlr-error-recovery-and-reporting Sometimes you want exceptions to pop out of the lexer--usually when you want to abort the entire parsing process upon syntax error. Antlr4 Error Handling asked 4 years ago viewed 240 times Blog How We Make Money at Stack Overflow: 2016 Edition Upcoming Events 2016 Community Moderator Election ends in 5 days Related 2Problem in compiling Antlr Error Handling Althouth it's not exactly what I wanted (i.e.

The default behavior of emitErrorMessage() is to print the error string to System.err. http://apexintsoft.com/error-handling/antlr-c-error-handling.php I had an action in the rule handhistory (not included in my previos post) which prints out each matched game. B ; ANTLR generates: match(A); if (!(false)) throw new SemanticException("false"); match(B); You can throw this exception yourself during the parse if one of your actions determines that the input is wacked. I defined and added a SyncParser rule to my grammar. Antlr Documentation

ANTLR will then invoke this empty rule but will first place the Follow set for that rule on the recovery stack. MismatchedTokenException Thrown by Parser.match() when it is looking for a token, but finds a different one on the input stream. Do only black holes emit gravitational waves? Check This Out Inspecting the default implementation (in the Java runtime) we find that the match method will call the method recoverFromMismatchedToken() and this in turn will try to use the current Follow set

Finding The nth Prime such that the prime - 1 is divisible by n Rounding a number up to the nearest multiple of a power of 2 Why do Internet forums In error recovery mode, Parser.consume() adds symbols to the parse tree by calling ParserRuleContext.addErrorNode(Token) instead of ParserRuleContext.addChild(Token). This meant I could fo this.

TODO: what to do about lexers Method Summary Methods Modifier and Type Method and Description boolean inErrorRecoveryMode(Parserrecognizer) Tests whether or not recognizer is in the process

What is the role of conjectures in modern mathematics? Here is an example that uses a bogus semantic exception (which is a subclass of RecognitionException) to demonstrate blasting out of the lexer: class P extends Parser; { public static void The only bug here is the fact that DefaultErrorStrategy did not parse the input successfully, which is actually a previously known bug that occurs so rarely that it's not a problem If you examine a method generated for a parser rule in the Java target, you will see that the rule logic is encapsulated within a try {} catch {} block, which

If the error strategy successfully recovers from the match failure, this method returns the Token instance which should be treated as the successful result of the match. I didn't test this. Perhaps you do not want the spurious/missing error detection? http://apexintsoft.com/error-handling/antlr-error-handling-c.php encountering the invalid token should not exit the configuration rule (antlr throws an exception on the invalid token), but should flag the issue and continue processing all the future config elements.

The typical main or parser invoker has try-catch around the invocation: try { ... } catch(TokenStreamException e) { System.err.println("problem with stream: "+e); } catch(RecognitionException re) { System.err.println("bad input: "+re); } Lexer Parameters:recognizer - the parser instance recoverInline TokenrecoverInline(Parserrecognizer) throws RecognitionException This method is called when an unexpected symbol is encountered during an inline match operation, such as Parser.match(int). Alex Report message to a moderator Re: Custom Syntax Error Recovery [message #1062482 is a reply to message #1062309] Sat, 08 June 2013 01:08 David Pizarro De La Skip to content Skip to breadcrumbs Skip to header menu Skip to action menu Skip to quick search Linked ApplicationsLoading…Confluence Spaces People Quick Search Help Online Help Keyboard Shortcuts Feed Builder

Clearly, when we return from an attempted parse of a classMember, we need to ensure that we resync the input stream to either the start of a new classMember, or the Different RAID settings for different folders on the same logical drive Goodness Giza Golf! Browse other questions tagged java parsing error-handling antlr grammar or ask your own question. but thanks before lex li –Berto Tuwondila Feb 22 '12 at 6:43 I cannot give you a Java example, as I use ANTLR in C#.

Depending on the complexity of the language that might even be the case for line breaks between elements. In all cases, the recursive-descent functions on the call stack are exited until an exception handler is encountered for that exception type or one of its base classes (in non-object-oriented languages,