Support RedHat 8.x on official Zed binaries (glibc 2.28)

[Timmmm]

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Describe the bug / provide steps to reproduce it

Zed currently requires glibc 2.29, which is not available on older Linux distros. I'm using RHEL 8 which only has 2.28.

I thought using the unofficial Flatpak version would work around this (isn't that the point of Flatpak?) but no, exactly the same issue. Soured my opinion of Flatpak a bit tbh, if it doesn't even avoid Linux's biggest binary compatibility clusterfuck.

Anyway is there any chance you could compile Zed with an older version? E.g. you could use Rocky 8. Here's an example where I did this.

Environment

RHEL 8 / Glibc 2.28

If applicable, add mockups / screenshots to help explain present your vision of the feature

No response

If applicable, attach your Zed.log file to this issue.

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[notpeter]

For reference, our official binaries for the GUI do not support RHEL 8.x, but the zed-remote-server binaries do (no glibc requirement at all).

You can absolutely build from source on Redhat 8.x. You should be able to follow the normal Building Zed for Linux docs. I recommend you checkout tags that match our released versions (e.g. v0.162.3 or whatever) as a random commit off main may be less stable.

To be honest, we don't have official RHEL 8.x compatible binaries because the primary use case for old RHEL and clones was for zed-remote-server. I put in the bulk of the work here to make sure it could build on almalinux:8 under Docker, but you're the first person to actually request builds for RHEL 8.x:

• Support More Linux #18480

There's some extra complexity for creating our CI release builds under Docker, but nothing too crazy. I'll see if I can get it going.

[Timmmm]

Ugh I had a whole comment here and then Linux's brilliant memory management kicked in and hard rebooted my machine (obviously what desktop users want when you run out of memory!).

Anyway TL;DR, I tried building from source and had two issues:

1. linux/script tries to enable the crb DNF repo but on RHEL8 it's actually codeready-builder-for-rhel-8-x86_64-rpms (who can keep track of this stuff?)
2. It tries to use mold even if you don't have Mold installed. I don't know if there's any way of making mold optional in .cargo/config.toml but I would suggest at least adding a warning box to the Building Zed for Linux page. It doesn't mention Mold at all, and most people probably don't have it so I think almost everyone would run into this?

Apart from that it built perfectly! Took a while, but nothing crazy considering how big of a project it is.

[notpeter]

1. Happy to accept PRs to make script/linux work on RHEL 8.x
2. Yeah, I believe our build scripts now require mold. Looks like script/linux should've outputted something if mold was unavailable:
   

   zed/script/linux

   Lines 11 to 20 in 489900e

   	function finalize {
   	# after packages install (curl, etc), get the rust toolchain
   	which rustup > /dev/null 2>&1 || curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y
   	# verify the mold situation
   	if ! command -v mold >/dev/null 2>&1; then
   	echo "Warning: Mold binaries are unavailable on your system." >&2
   	echo " Builds will be slower without mold. Try: script/install-mold" >&2
   	fi
   	echo "Finished installing Linux dependencies with script/linux"
   	}

   
   Perhaps that message should more explicitly say "ERROR" not "WARNING".

We have a dedicated script for installing mold, crazily named script/install-mold. I have been hesitant to call this by default from script/linux since it just downloads a binary from github releases and plops it in /usr/local/bin/mold -- since everything else in script/linux only downloads official distribution packages, I'd rather be a good houseguest and only plop binaries in /usr/local/bin when explicitly asked to. Similar problems occur with very old distros and cmake versions, see also script/install-cmake.

Anyways, happy to review PRs to improve this process or documentation. I did my best, but without a RHEL 8.x license I can only test on clones (Rocky, Alma, etc) which only goes so far. Thanks for the feedback.