From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from NAM12-BN8-obe.outbound.protection.outlook.com (mail-bn8nam12on2111.outbound.protection.outlook.com [40.107.237.111]) by sourceware.org (Postfix) with ESMTPS id A06FD3857C41 for ; Mon, 31 Aug 2020 22:08:37 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org A06FD3857C41 ARC-Seal: i=1; a=rsa-sha256; s=arcselector9901; d=microsoft.com; cv=none; b=UVVOiTViPtBH02hgqm5w935QiVfGhX8Q+H2y9J120+fBo8yR9SjV6n3cSY5snu67vQxn9hubgjx1GNElMfPSRUF0MEOy3o72ZWWqrtlSIlZZ5j1gj2pLaKo5xATMZ7lO2UTKMWoWpKuV8HWfNMl0zULEGKonOHpCEd6H9K51chNCOud4Uow6G8UTxXPVAa53Xhnc2ZjkYgR24AOKhQsjTeLiX6G4PdTZl9cL7mpTvfs7tVO+XgAT2dL8kyJ0LFV+hpmKCZzdsUBPPA4MrgRKoKyj6rXpcxDIP9VWMkcvpCLiDeesviS5e9V4z0F5i3HWCZMpF6uA+k8se/9xe+xLCw== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector9901; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=qvaRlZTmw7wyIbqOROYvYmfgUZQnTXWRR1A5YZ4Kk4M=; 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This new release, > version 2.48.4-2, has been rebuilt with OCaml 4.08.1, which makes it > compatible for syncing with Ubuntu Focal and the current Debian testing. > > *Warning*: This update may be a breaking change, if you use unison2.48 to > synchronize with hosts that run other Linux distros. This is because two > Unison executables have to be built with the same version of OCaml in order > to be compatible. For discussion of this newly-discovered problem and how > we plan to deal with it in Cygwin, see OCaml Versions, below. [...] > == OCaml Versions > > There is unfortunately another layer of incompatibility in Unison: Two > Unison executables are only compatible if they were built with the same > version of OCaml. If you use, say, Unison 2.48 on two different hosts, but > one was built with OCaml 4.08.1 and the other with OCaml 4.10.0, you'll get > the dreaded error message > > Fatal error: Fatal error during unmarshaling (input_value: ill-formed > message), possibly because client and server have been compiled with > different versions of the OCaml compiler. > > This is a bad feature, of OCaml apparently. It means that in order to be > sure of being able to sync with another host, we could potentially need a > separate Unison package for every combination of Unison and OCaml. > > For now, Unison packages for Cygwin are being built with the OCaml version > that seems to make them most generally compatible with other Linux distros: > > Package OCaml version Compatibility > ---------- ------------- ------------- > unison2.27 ? ? > unison2.32 ? ? > unison2.40 ? ? > unison2.45 ? ? > unison2.48 4.08.1 Debian bullseye (testing), Ubuntu Focal > unison2.49 ? ? > unison2.51 ? ? > > Packages with "?" are older builds, where the OCaml version isn't currently > known. > > If your distro uses a different combination of Unison and OCaml versions > that you need in order to sync, please let me know here. If it's widely > used, I might update one of the existing builds, or make a new Cygwin > package for it. What a mess! Would you consider embedding the OCaml version in the package name as suggested by the Debian maintainer (http://lists.seas.upenn.edu/pipermail/unison-hackers/2020-August/001975.html)? Thus unison2.48-2.48.4-1 would be replaced by something like unison2.48+4.04.1... and unison2.48-2.48.4-2 would be replace by something like unison2.48+4.08.1.... That way people who are happy with unison2.48-2.48.4-1 can keep using it without being pestered by setup to update. FWIW, here's my situation, which is probably not typical. When you released unison2.48-2.48.4-1 a few years ago, it was incompatible with the Linux server that I sync with. So I simply built OCaml and unison myself on that server, using the same versions that you used, and installed unison in my own ~/bin directory. I could do that again, now using OCaml 4.08.1. But I'd much rather just keep my current arrangement, without having setup try to update unison2.48 every time I run it. Ken