FuelLabs/sway · error

non-configurable found in configurables region of the data s

Error message

non-configurable found in configurables region of the data section

What it means

This panic fires during bytecode finalization in to_bytecode while building the map of configurable names to their absolute offsets. Every entry in data_section.configurables must carry an EntryName::Configurable; if the let-else pattern fails, an entry whose name is a different variant (e.g. a blob or non-configurable datum) ended up in the configurables region, meaning the data section was constructed incorrectly upstream (entries placed in the wrong region).

Source

Thrown at sway-core/src/asm_generation/finalized_asm.rs:323

        for (i, entry) in data_section.iter_all_entries().enumerate() {
            let entry_offset = data_section.absolute_idx_to_offset(i);
            print_entry(indentation, offset + entry_offset, &entry);
        }

        println!(";; --- END OF TARGET BYTECODE ---\n");
    }

    assert_eq!(half_word_ix * 4, offset_to_data_section_in_bytes as usize);
    assert_eq!(bytecode.len(), offset_to_data_section_in_bytes as usize);

    let named_data_section_entries_offsets = data_section
        .configurables
        .iter()
        .enumerate()
        .map(|(id, entry)| {
            let EntryName::Configurable(name) = &entry.name else {
                panic!("non-configurable found in configurables region of the data section");
            };
            (
                name.clone(),
                offset_to_data_section_in_bytes
                    + data_section.data_id_to_offset(&DataId {
                        idx: id as u32,
                        region: DataSectionRegion::Configurables,
                    }) as u64,
            )
        })
        .collect::<BTreeMap<String, u64>>();

    let mut data_section = data_section.serialize_to_bytes();
    bytecode.append(&mut data_section);

    CompiledBytecode {
        bytecode,
        named_data_section_entries_offsets,

View on GitHub (pinned to dad95cc42b)

Solutions

1. Fix data section construction so only entries named EntryName::Configurable are pushed into the configurables region
2. Audit the code paths that build DataSection.configurables (e.g. configurables collection during codegen) and ensure region assignment matches the entry name variant
3. Add a debug assertion or validation when entries are inserted into the configurables region so the mismatch is caught earlier with a better diagnostic

When it happens

Trigger: Thrown at sway-core/src/asm_generation/finalized_asm.rs:323 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of FuelLabs/sway@dad95cc42b (2026-09-04). Data as JSON: /api/errors/3a0e01d7e82c56c1. Report an issue: GitHub.