The motivation for this change is that we have continued failures that are specific to these old operating systems and don't have the resources on engineering teams to prioritize these bugs. Especially with the deployment of e10s we're seeing intermittent and permanently [sic] failures on MacOS 10.6 that we are not seeing elsewhere.
This confirms my suspicions that Electrolysis would have been seriously problematic on 10.4 and 10.5 given the permafails Mozilla is seeing on 10.6, even if we got it to compile (it doesn't even do that on Tiger yet). That's why we're forking after 45ESR, which doesn't have E10S enabled by default.
Interestingly, Mozilla's plan is nearly identical to ours: move 10.6-10.8 users onto 45ESR as well so that they'll still get a year-ish of support on that branch in a sort of graceful wind-down. The difference is that we plan to make hacks to the core to support certain post-45 features (making TenFourFox essentially into an OS X Classilla), and of course backport future security updates from 52ESR and so on. I guess if you're running Snow Leopard you can use TenFourFox post-fork with the usual limitations, but I still currently have no plans for an Intel-native version unless someone steps up to maintain it (although I have a 10.6 machine that might benefit, I just don't have the time right now).
The interesting part is that Mozilla still has more users on 10.6 than 10.7 and 10.8 combined, and 10.6 still accounts for something like 13% of all Firefox Mac users. As late as 2014 19% of all Macs ran it. Snow Leopard really is the Windows XP of the Intel Mac.
Mozilla also did a wholesale pruning of most of the other Tier-3 ports, as part of shifting from autoconf:
Following our official move off autoconf, the core build team is faced with having to convert more than 17k lines of shell+m4. A large part of those are to support Tier-3 platforms such as Solaris, HPUX, AIX, etc., with compilers that are not MSVC, GCC or clang (e.g. SunPro, XL C++...). To simplify the conversion, from day one, we will support only the following set of platforms and toolchains:
- multiple flavors of BSD (kFreeBSD, FreeBSD, DragonFly, NetBSD, OpenBSD)
This is a little different than the end of 10. support, however:
This does not mean Firefox/Gecko/etc. will forever drop support for these platforms and toolchains. It simply means we can't assess what parts of the shell+m4 are relevant (as opposed to cruft accumulated over years or decades) and will continue to work (since we don't have automation to verify these configurations).
The good news is that dropping support now will help make the overall conversion happen sooner, *and*, once the conversion is done, interested parties can come back with working patches that should be easier to write.
My SPARC Ultra-3 laptop (a rebadged Tadpole Viper) runs an ESR build of Firefox just fine in Solaris 10, the last Solaris supported on that platform. Unfortunately I don't have the Sun compiler, or I'd take a whack at building it myself. At least someone out there is still popping out contrib builds for SPARC and i386, but I don't know if they will continue to.
On the other hand, some of those other platforms haven't worked in years. I know of a Firefox 3.6 for AIX, at least on POWER (my PowerPC AIX systems barf on it), but HP/sUX ended support somewhere around 3.5.9 and was always a mess to build (I hated HP's ANSI C-compiler back in the day when I had to administer those systems). I even remember seeing some Digital UNIX/Tru64 stuff deep within xpcom/, but I can't imagine full support persisted much beyond Mozilla 1.8 something. None of the rest of them got much further.
Really, these are all dusty legacies of how portable the old codebase used to be. At one time, Netscape ran on Windows (as early as 3.1), Mac OS (System 7 and up), OS/2, Linux, Digital UNIX (Tru64), SunOS 4, VMS (VAX and Alpha), Solaris, BSD, HP/UX, IRIX, AIX, and probably some other minority ports I don't remember, and all with almost total feature parity. In fact, I myself have personally used every single one of those ports at one time or another. As late as Mozilla 1.7 almost all of those platforms were still working (SunOS 4 and VMS were gone, and Mac OS was replaced with OS X, but the rest were still functioning), but Firefox 2 and 3 gradually winnowed the rest, and by Firefox 4 it was pretty much just Windows, OS X (including us), Linux, the BSDs and Solaris. Soon it'll just be those OSes on x86-64 and ARM.
So, while it may have been hell to maintain, that's a lot of history gone that I personally lived through and good cause or not it still makes me sad to see these last remnants drift away, even on the abandoned platforms. (You can cram it if you're going to post some uninsightful comment like "paying back technological debt" or "no one maintains platforms for free." I'm well aware of the cost of cruft. That doesn't mean it doesn't have historical value, and that historical value should be appreciated, even if doing so is best done in archives rather than current code bases.) It used to be neat to compare how heterogeneous and diverse computing platforms were back in the day, but sadly today's platforms are more alike than they're different, and I think we've lost something there.
It's not really fun anymore.