GitoxideLabs/gitoxide · error

LEB64 value overflowed

Error message

LEB64 value overflowed

What it means

gix-features' LEB64 decoder (`leb64_from_read`, used by `from_read`) decodes variable-length 64-bit integers byte by byte with checked arithmetic. This error is raised when the accumulated value would overflow a `u64`, meaning the input stream contains more continuation bytes than a valid LEB64 u64 can have — i.e. malformed or corrupt encoded data.

Solutions

1. Verify the integrity of the source data (pack checksum) before decoding.
2. Re-download or re-generate the binary input; the value cannot be represented in u64.
3. If handling untrusted input, treat this as expected: catch the io::Error with kind InvalidData and reject the input.

match gix_features::decode::leb64(&mut reader) {
    Err(e) if e.kind() == std::io::ErrorKind::InvalidData => /* reject: corrupt varint input */,
    other => /* continue */,
}

When it happens

Trigger: Calling `gix_features::decode::leb64` / `from_read` on data with 10+ continuation bytes (high bit set), typically from a truncated, corrupted, or adversarially crafted binary stream.

Common situations: Reading damaged pack/idx binary data, fuzzing the decoder, or feeding a decoder bytes from the wrong offset so varint boundaries shift.

Understand the failure class

Background: "value must be between 0 and 1" / "out of range" / "must not be negative" errors: fixing range-validation failures across open-source libraries — this error's family across 42 libraries.

Related errors

• Failed to subtract from
• base graph count to fit in 32-bits
• number of commits in CDAT chunk to fit in 32 bits
• ' ' is not a valid configuration key
• Cannot use iter_v1() on index of type

AI-assisted analysis of GitoxideLabs/gitoxide@e73179060b (2026-09-08). Data as JSON: /api/errors/d93c4bf0632046f1. Report an issue: GitHub.

Appendix: source

Thrown at gix-features/src/decode.rs:19

use std::io::Read;

/// Decode variable int numbers from a `Read` implementation.
#[inline]
pub fn leb64_from_read(mut r: impl Read) -> Result<(u64, usize), std::io::Error> {
    let mut byte = [0u8; 1];
    r.read_exact(&mut byte)?;
    let mut c = byte[0];
    let mut i = 1;
    let mut value = u64::from(c) & 0x7f;
    while c & 0x80 != 0 {
        r.read_exact(&mut byte)?;
        c = byte[0];
        i += 1;
        value = value
            .checked_add(1)
            .and_then(|value| value.checked_shl(7))
            .and_then(|value| value.checked_add(u64::from(c) & 0x7f))
            .ok_or_else(|| std::io::Error::new(std::io::ErrorKind::InvalidData, "LEB64 value overflowed"))?;
    }
    Ok((value, i))
}

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