Clinton Mead
Thanks all for your replies. Just going through what Ben has said step by step:
My sense is that if you don't need the threaded runtime system it would
probably be easiest to just try to make a modern GHC run on Windows XP.
Happy to run non-threaded runtime. A good chunk of these machines will be single or dual core anyway.
That indeed somewhat simplifies things.
As Tamar suggested, it likely not easy, but also not impossible. WinIO is indeed problematic, but thankfully the old MIO IO manager is still around (and will be in 9.2).
"Is still around"? As in it's in the code base and just dead code, or can I trigger GHC to use the old IO manager with a GHC option?
The possible reasons for Windows XP incompatibility that I can think of
off the top of my head are:
* Timers (we now use QueryPerformanceCounter)
This page suggests that QueryPerformanceCounter https://docs.microsoft.com/en-us/windows/win32/api/profileapi/nf-profileapi-... should run on XP. Is this incorrect?
It's supported, but there are caveats [1] that make it unreliable as a timesource. [1] https://docs.microsoft.com/en-us/windows/win32/sysinfo/acquiring-high-resolu...
* Big-PE support, which is very much necessary for profiled builds
I don't really need profiled builds
Alright, then you *probably* won't be affected by PE's symbol limit.
* Long file path support (mostly a build-time consideration as Haskell build systems tend to produce very long paths)
I don't need to build on Windows XP either. I just need to run on Windows XP so hopefully this won't be an issue. Although if GHC was modified for long file path support so it could build itself with long file path support presumably it will affect everything else it builds also.
If you don't need to build on XP then I suspect this won't affect you.
There may be others, but I would start looking there. I am happy to answer any questions that might arise.
I'm guessing the way forward here might be a patch with two options:
1. -no-long-path-support/-long-path-support (default -long-path-support) 2. -winxp
The winxp option shall:
- Require -no-long-path-support - Conflicts with -threaded - Conflicts with profiled builds - Uses the old IO manager (I'm not sure if this is an option or how this is done).
The old IO manager is still the default, although this will likely change in 9.2.
What do you think (roughly speaking)?
Yes, that is essentially correct. I would probably start by trying to run a 32-bit GHC build on Windows XP under gdb and see where things fall over. Cheers, - Ben