antlr/antlr4 · error · IOException

Could not create checksum {}

Error message

Could not create checksum {}

What it means

The inverse delimiter imbalance in split(pattern): more stop delimiters than start delimiters means a stop appeared with no matching start, so 'missing start tag' IllegalArgumentException is thrown. The scanner cannot decide which text belongs to a tag versus literal text when the pairing is broken.

Source

Thrown at antlr4-maven-plugin/src/main/java/org/antlr/mojo/antlr4/MojoUtils.java:47

            MessageDigest complete = MessageDigest.getInstance("MD5");

            try {
                int n;

                do {
                    n = in.read(buffer);

                    if (n > 0) {
                        complete.update(buffer, 0, n);
                    }
                } while (n != -1);
            } finally {
                in.close();
            }

            return complete.digest();
        } catch (NoSuchAlgorithmException ex) {
            throw new IOException("Could not create checksum " + file, ex);
        }
    }

    /**
     * Given the source directory File object and the full PATH to a grammar, produce the
     * path to the named grammar file in relative terms to the {@code sourceDirectory}.
     * This will then allow ANTLR to produce output relative to the base of the output
     * directory and reflect the input organization of the grammar files.
     *
     * @param   sourceDirectory  The source directory {@link File} object
     * @param   grammarFileName  The full path to the input grammar file
     *
     * @return  The path to the grammar file relative to the source directory
     */
    public static String findSourceSubdir(File sourceDirectory, File grammarFile) {
        String srcPath = sourceDirectory.getPath() + File.separator;
        String path = grammarFile.getPath();

View on GitHub (pinned to 7d5770395b)

Solutions

1. Escape literal '>' characters in text chunks with the escape sequence (e.g. \\>).
2. Use custom delimiters that do not occur in the target syntax.
3. Lint patterns for balanced delimiters before compiling.

Example fix

// before
ParseTreePattern p = m.compile("a > <ID>", R.expr); // stray '>' counts as stop

// after
ParseTreePattern p = m.compile("a \\> <ID>", R.expr);

long starts = pattern.chars().filter(c -> c == '<').count();
long stops  = pattern.chars().filter(c -> c == '>').count();
if (starts < stops) throw new IllegalArgumentException("missing start tag: " + pattern);

boolean hasBalancedTags(String p) {
    return p.chars().filter(c -> c=='<').count() == p.chars().filter(c -> c=='>').count();
}

try {
    pattern = matcher.compile(patternText, ruleIndex);
} catch (IllegalArgumentException e) {
    if (e.getMessage().startsWith("missing start tag")) {
        patternText = escapeLiteralStops(patternText);
        pattern = matcher.compile(patternText, ruleIndex);
    } else throw e;
}

When it happens

Trigger: Patterns like "ID> = <ID>" (stray '>' in text), or text containing the stop delimiter character without it being part of a tag.

Common situations: Matching expression grammars whose literal text includes '>' (comparisons, generics-like syntax, arrows '->'); forgetting to escape a literal stop delimiter.

Related errors

• Cannot handle relative paths containing '..'
• expected {} to be prefixed with {}
• index cannot be negative
• missing interface implementation
• Fatal error occured while evaluating the names of the gramma

AI-assisted analysis of antlr/antlr4@7d5770395b (2026-08-14). Data as JSON: /api/errors/0a19cc44014e55c2. Report an issue: GitHub.