How to install protobuf compiler v3?

[divagant-martian]

I'm trying to install the protobuf compiler version 3 but I keep getting v2

A minimum working example:

// cargo new --bin cross_example
// contents of src/main.rs
use std::process::Command;

fn main() {
    let output = Command::new("protoc")
        .arg("--version")
        .output()
        .expect("protoc should be installed");
    println!("Output: {}", String::from_utf8_lossy(&output.stdout));

    let output = Command::new("cat")
        .arg("/etc/apt/sources.list")
        .output()
        .expect("cat should be installed");
    println!("Output: {}", String::from_utf8_lossy(&output.stdout));
}

the Cross.toml

[target.x86_64-unknown-linux-gnu]
pre-build = ["apt update && apt upgrade && apt install -y protobuf-compiler"]

the output

Output: libprotoc 2.6.1

Output: # See http://help.ubuntu.com/community/UpgradeNotes for how to upgrade to
# newer versions of the distribution.
deb [arch=amd64,i386] http://archive.archive.ubuntu.com/ubuntu/ xenial main restricted
# deb-src [arch=amd64,i386] http://archive.archive.ubuntu.com/ubuntu/ xenial main restricted

## Major bug fix updates produced after the final release of the
## distribution.
deb [arch=amd64,i386] http://archive.archive.ubuntu.com/ubuntu/ xenial-updates main restricted
# deb-src [arch=amd64,i386] http://archive.archive.ubuntu.com/ubuntu/ xenial-updates main restricted

## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
## team. Also, please note that software in universe WILL NOT receive any
## review or updates from the Ubuntu security team.
deb [arch=amd64,i386] http://archive.archive.ubuntu.com/ubuntu/ xenial universe
# deb-src [arch=amd64,i386] http://archive.archive.ubuntu.com/ubuntu/ xenial universe
deb [arch=amd64,i386] http://archive.archive.ubuntu.com/ubuntu/ xenial-updates universe
# deb-src [arch=amd64,i386] http://archive.archive.ubuntu.com/ubuntu/ xenial-updates universe

## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
## team, and may not be under a free licence. Please satisfy yourself as to
## your rights to use the software. Also, please note that software in
## multiverse WILL NOT receive any review or updates from the Ubuntu
## security team.
deb [arch=amd64,i386] http://archive.archive.ubuntu.com/ubuntu/ xenial multiverse
# deb-src [arch=amd64,i386] http://archive.archive.ubuntu.com/ubuntu/ xenial multiverse
deb [arch=amd64,i386] http://archive.archive.ubuntu.com/ubuntu/ xenial-updates multiverse
# deb-src [arch=amd64,i386] http://archive.archive.ubuntu.com/ubuntu/ xenial-updates multiverse

## N.B. software from this repository may not have been tested as
## extensively as that contained in the main release, although it includes
## newer versions of some applications which may provide useful features.
## Also, please note that software in backports WILL NOT receive any review
## or updates from the Ubuntu security team.
deb [arch=amd64,i386] http://archive.archive.ubuntu.com/ubuntu/ xenial-backports main restricted universe multiverse
# deb-src [arch=amd64,i386] http://archive.archive.ubuntu.com/ubuntu/ xenial-backports main restricted universe multiverse

## Uncomment the following two lines to add software from Canonical's
## 'partner' repository.
## This software is not part of Ubuntu, but is offered by Canonical and the
## respective vendors as a service to Ubuntu users.
# deb http://archive.canonical.com/ubuntu xenial partner
# deb-src http://archive.canonical.com/ubuntu xenial partner

deb [arch=amd64,i386] http://security.archive.ubuntu.com/ubuntu/ xenial-security main restricted
# deb-src [arch=amd64,i386] http://security.archive.ubuntu.com/ubuntu/ xenial-security main restricted
deb [arch=amd64,i386] http://security.archive.ubuntu.com/ubuntu/ xenial-security universe
# deb-src [arch=amd64,i386] http://security.archive.ubuntu.com/ubuntu/ xenial-security universe
deb [arch=amd64,i386] http://security.archive.ubuntu.com/ubuntu/ xenial-security multiverse
# deb-src [arch=amd64,i386] http://security.archive.ubuntu.com/ubuntu/ xenial-security multiverse

The first output shows the protoc version as 2.6.1, the version was upgraded to v3 in ubuntu 18.04, however the sources indicate it's running in ubuntu xenial (16.04) but as far as I can tell the cross bases use ubuntu 20.04.

So how can ensure a newer ubuntu version is used to get the right protobuf compiler? My cross version is 0.2.4

[Emilgardis]

in cross 0.2.4 ubuntu is indeed 18.04, if you instead install cross from main you'll have the new images, which should have the version you want

cargo install cross --git https://github.com/cross-rs/cross

the 20.04 images are scheduled to be released in 0.3.0, for now use cross from the main branch

[divagant-martian]

Thanks for the answer. I'll do that! I'm still curious since what I see indicates cross 0.2.4 uses Ubuntu 16.04, not 18.04. Ubuntu 18.04 would actually solve my problem as well

[divagant-martian]

More specifically, this

$ docker run -ti ghcr.io/cross-rs/x86_64-unknown-linux-gnu:latest
root@4568f7109a2c:/# cat /etc/issue
Ubuntu 16.04.7 LTS \n \l

[Alexhuszagh]

@divagant-martian Try using main or do docker pull $image. By default, docker run and cross don't pull images before running them, so if you have a v0.2.x image locally, it will always use that until you upgrade.

[Emilgardis]

Thanks for the answer. I'll do that! I'm still curious since what I see indicates cross 0.2.4 uses Ubuntu 16.04, not 18.04. Ubuntu 18.04 would actually solve my problem as well

My bad, mentioned the wrong version :) Yes, 16.04 is the current version in latest, with main you'll get 20.04