tar archive file with LABEL fails to iterate `entries()`

[jtmoon79]

tl;dr a archive.tar with a label, i.e. tar --label my-label -cf archive.tar ..., will fail to iterate over entries

Reproduction

Given these project files

main.rs

use std::env;
use std::fs::File;
use std::io;

use tar::Archive;

fn run() -> Result<(), Box<dyn std::error::Error>> {
    let mut args = env::args();
    let program_name = args.next().unwrap_or_else(|| "tar_bug_1".to_string());

    let tar_path = match (args.next(), args.next()) {
        (Some(path), None) => path,
        _ => {
            eprintln!("Usage: {program_name} <path-to-tar-file>");
            return Err(io::Error::new(
                io::ErrorKind::InvalidInput,
                "expected exactly one argument",
            )
            .into());
        }
    };

    let file = File::open(&tar_path)?;
    let mut archive = Archive::new(file);

    eprintln!("archive.entries()...");
    let entry_iter: tar::Entries<File> = match archive.entries() {
        Ok(val) => val,
        Err(err) => {
            eprintln!("archive.entries() Err; {:?}", err);
            return Err(err.into());
        }
    };
    eprintln!("for entry_result in entry_iter...");
    for entry_result in entry_iter {
        let entry = match entry_result {
            Ok(val) => val,
            Err(err) => {
                eprintln!("entry_result Err; {:?}", err);
                continue;
            }
        };
        let path = entry.path()?;
        println!("{}", path.display());
    }

    eprintln!("Ok");
    Ok(())
}

fn main() {
    if let Err(err) = run() {
        eprintln!("Error: {err}");
        std::process::exit(1);
    }
}

Cargo.toml

[package]
name = "tar_bug_1"
version = "0.1.0"
edition = "2024"

[dependencies]
tar = "0.4.44"

steps

Create the file archive.tar with a label and some files

$ echo "A" > a.txt
$ echo "BB" > b.txt
$ tar -v -c --label MY_TAR_LABEL -f archive.tar ./a.txt ./b.txt
MY_TAR_LABEL
./a.txt
./b.txt

Print the entries in archive.tar

$ cargo run -- ./archive.tar
archive.entries()...
for entry_result in entry_iter...
Error: numeric field was not a number:  when getting size for MY_TAR_LABEL
Ok

ERROR: the iteration over archive.entries() ceases
ACTUAL: the iteration over archive.entries() to be able to continue

sanity check program

Test with a tar file without a label, just to be sure the program works for other tar files

$ tar -v -c -f archive_no_label.tar ./a.txt ./b.txt
./a.txt
./b.txt

$ cargo run -- ./archive_no_label.tar
archive.entries()...
for entry_result in entry_iter...
./a.txt
./b.txt
Ok

Observed environment

• Ubuntu 24
• crate tar 0.4.44
• GNU tar 1.35
• rust 1.91.0