oracle/graal · error · TypeError

unexpected tuple size for jvmci variant {variant} (size must

Error message

unexpected tuple size for jvmci variant {variant} (size must be <= 4)

What it means

mx SDK benchmark harness error raised when registering JVMCI VM variants: each variant tuple in suite configuration must have 2, 3, or 4 elements (name, args[, priority[, compiler_config]]). A tuple of any other length is a configuration-authoring mistake and raises TypeError immediately during add_vm suite setup.

Source

Thrown at sdk/mx.sdk/mx_sdk_benchmark.py:220

    if hosted:
        prefixes.append(('hosted-', ['-XX:-UseJVMCICompiler']))
    for prefix, args in prefixes:
        extended_raw_config_name = prefix + raw_config_name
        extended_extra_args = extra_args + args
        if include_default:
            mx_benchmark.add_java_vm(
                JvmciJdkVm(raw_name, extended_raw_config_name, extended_extra_args), suite, priority)
        for variant in variants:
            compiler_config = None
            if len(variant) == 2:
                var_name, var_args = variant
                var_priority = priority
            elif len(variant) == 3:
                var_name, var_args, var_priority = variant
            elif len(variant) == 4:
                var_name, var_args, var_priority, compiler_config = variant
            else:
                raise TypeError(f"unexpected tuple size for jvmci variant {variant} (size must be <= 4)")

            variant_args = extended_extra_args + var_args
            if compiler_config is not None:
                variant_args = add_or_replace_arg('-Djdk.graal.CompilerConfiguration', compiler_config, variant_args)

            mx_benchmark.add_java_vm(
                JvmciJdkVm(raw_name, extended_raw_config_name + '-' + var_name, variant_args), suite, var_priority)


class GraalVm(mx_benchmark.OutputCapturingJavaVm):
    def __init__(self, name, config_name, extra_java_args, extra_launcher_args):
        """
        :type name: str
        :type config_name: str
        :type extra_java_args: list[str] | None
        :type extra_launcher_args: list[str] | None
        """
        super().__init__()

View on GitHub (pinned to a66e9ccd1d)

Solutions

Inspect the variants list passed to the JVMCI registration and fix each entry to (name, args), (name, args, priority), or (name, args, priority, compiler_config).
Check for accidental trailing commas ('graal',) that create 1-tuples.
If you need a new field, extend the branch chain in mx_sdk_benchmark.py itself rather than appending extra tuple elements.

Example fix

# before
variants = [('graal', '-XX:+UseJVMCICompiler', 1, 'community', 'extra')]

# after
variants = [('graal', '-XX:+UseJVMCICompiler', 1, 'community')]

Defensive patterns

Strategy: validation

Validate before calling

def validate_variants(variants):
    for v in variants:
        if not isinstance(v, tuple) or len(v) not in (2, 3, 4):
            raise ValueError(f"bad jvmci variant tuple: {v!r} (need len 2-4)")
    return variants

Type guard

def is_valid_jvmci_variant(v) -> bool:
    return isinstance(v, tuple) and len(v) in (2, 3, 4) and isinstance(v[0], str) and isinstance(v[1], (str, list))

Try / catch

Wrap suite registration in try/except TypeError during config loading and report the offending tuple to the user; fail fast at config parse time rather than mid-benchmark.

Prevention

Validate variant tuples in a unit test for your suite config.
Watch for trailing commas creating 1-tuples.
Document the accepted shapes (2/3/4 elements) next to the variants list.

When it happens

Trigger: Calling the JVMCI VM registration helper with a variants list containing a 1-element or 5+-element tuple, e.g. variants = [('graal',), ...] or ('name', args, priority, config, extra). Trips before any benchmark runs, during mx benchmark suite initialization.

Common situations: Editing mx_sdk_benchmark-style suite definitions or suite.py benchmark configs in a downstream GraalVM distribution; typo like a trailing comma creating a 1-tuple, or passing a list instead of tuple so len() is wrong.

Related errors

AI-assisted analysis of oracle/graal@a66e9ccd1d (2026-08-14). Data as JSON: /api/errors/58a06451f72cf76a. Report an issue: GitHub.