GitoxideLabs/gitoxide · error

tree extension exceeds 4GB

Error message

tree extension exceeds 4GB

What it means

The git index TREE extension writer (`write_to` in gix-index) stores the total serialized length as a big-endian `u32`. If the accumulated entry bytes exceed `u32::MAX` (~4GB), `u32::try_from` fails and the writer returns `InvalidData` rather than emitting a structurally invalid index file.

Solutions

1. Reduce the size of the index/TREE extension data being written (fewer/smaller entries).
2. Verify entry construction for accidental duplication that inflates `entries.len()`.
3. File/track an upstream limitation — the git index format itself caps this field at u32.

match gix_index::extension::tree::write_to(&tree, &mut out) {
    Err(e) if e.to_string().contains("exceeds 4GB") => /* handle oversize index gracefully */,
    other => /* continue */,
}

When it happens

Trigger: Calling index writing with a TREE extension whose serialized entry data exceeds 4GB — an enormous repository with a gigantic tree extension.

Common situations: Monorepo-scale checkouts being rewritten by gix-based tooling; fuzz tests generating pathological index data; a bug duplicating entries during extension construction.

Understand the failure class

Background: "File too large" / "file size exceeds limit" errors: why libraries cap file sizes and how to fix them — this error's family across 46 libraries.

Related errors

• Cannot use iter_v1() on index of type
• Cannot use iter_v2() on index of type
• invalid mode change: can't flip executable bit of
• visit_non_tree() called us
• cannot create a commit with unresolved index conflicts

AI-assisted analysis of GitoxideLabs/gitoxide@e73179060b (2026-09-08). Data as JSON: /api/errors/eb636efd7e420377. Report an issue: GitHub.

Appendix: source

Thrown at gix-index/src/extension/tree/write.rs:43

            }

            for child in &tree.children {
                tree_entry(out, child, buf)?;
            }

            Ok(())
        }

        let signature = tree::SIGNATURE;

        let mut entries = Vec::<u8>::new();
        let mut num_buf = itoa::Buffer::new();
        tree_entry(&mut entries, self, &mut num_buf)?;

        out.write_all(&signature)?;
        out.write_all(
            &u32::try_from(entries.len())
                .map_err(|_| std::io::Error::new(std::io::ErrorKind::InvalidData, "tree extension exceeds 4GB"))?
                .to_be_bytes(),
        )?;
        out.write_all(&entries)?;

        Ok(())
    }
}

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