Скачать или смотреть Resolving StackOverflowError in ANTLR4: Parsing STRING_VALUE with Slashes

Learn how to fix the `StackOverflowError` during ANTLR4 parsing when using slashes in `STRING_VALUE`. Get tips on grammar adjustments and error handling in this detailed guide.
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Resolving StackOverflowError in ANTLR4: Parsing STRING_VALUE with Slashes

When working with ANTLR4, encountering errors during parsing can be frustrating, especially when it leads to a StackOverflowError. This issue often stems from how ANTLR is instructed to handle input values. If you’ve found yourself facing a StackOverflowError while parsing something as simple as a string containing slashes, this guide will help you troubleshoot the problem and adjust your grammar for successful parsing.

Understanding the Issue

In this case, the error arises from the following input:

[[See Video to Reveal this Text or Code Snippet]]

The parser expects STRING_VALUE to conform to certain rules outlined in the grammar. One of the culprits leading to the StackOverflowError is the way operators are recognized in your ANTLR grammar, particularly related to how the slash (/) interacts with the defined rules.

The StackOverflowError Explained

The stack trace shows that the error occurs when trying to add a bucket in the Array2DHashSet, which indicates that the parser is likely caught in a recursive loop instead of reaching a proper termination.

To resolve this issue, we need to adjust the grammar definition for STRING_VALUE, specifically regarding how slashes are treated.

Solution: Adjusting the Grammar

Method 1: Escaping the Slash

One straightforward solution is to modify the STRING_VALUE definition by escaping the slash. Update the rule like so:

[[See Video to Reveal this Text or Code Snippet]]

This adjustment tells the parser explicitly that slashes are valid within the defined set of characters.

Method 2: Altering the Order of Characters

Another approach is to change the order of defined characters in your lexer rules, ensuring that the slash is treated as a literal rather than a range operator.

For example, if you define your DATE_VALUE, it should look something like this:

[[See Video to Reveal this Text or Code Snippet]]

Here, you've placed the hyphen at the end of the set, which can prevent it from being interpreted as a range operator.

General Grammar Tips

As you refine your grammar, here are a few additional suggestions that can enhance your grammar design:

Keep It Simple: Try to keep rules as uncomplicated as possible. This helps avoid potential ambiguities and makes your grammar easier to understand.

Test Incrementally: As you add new rules or modify existing ones, test the scanner one rule at a time to quickly isolate issues.

Use Comments Effectively: Comment your code well to track your thought process and the intent behind each rule.

Refer to ANTLR Documentation: ANTLR's official documentation is a valuable resource for understanding features and syntactic rules.

Conclusion

Resolving a StackOverflowError during ANTLR4 parsing doesn't have to be a daunting task. By adjusting your STRING_VALUE and possibly your other definitions to either escape the special characters or redefine them, you can effectively prevent these issues from interrupting your workflow. Happy parsing!