[llvm-dev] RFC: A cross platform way of using shell commands in lit tests

Zachary Turner via llvm-dev llvm-dev at lists.llvm.org
Tue Aug 16 11:39:23 PDT 2016

That's only if you use git bash, not cmd.

On Tue, Aug 16, 2016 at 11:38 AM Reid Kleckner <rnk at google.com> wrote:

> One other thing to note is that the dependency problem is going to go away
> very soon just a result of moving to git. The normal Windows install of git
> comes with all the utilities you need to run the LLVM tests anyway. I
> haven't bothered to install gnuwin32 on my new machine.
> I think we do want to rewrite a few key utilities, like 'rm', to make them
> reliable on Windows, but for most things like 'grep' and 'sed', we should
> use the standard things. There's no reason to want to have our own subtly
> different versions of these tools.
> If we do go all the way to avoid process creation, then it becomes
> interesting to have our own version of these things, and at that point,
> maybe having a fork or checked-in copy of busybox is the way to go.
> On Tue, Aug 16, 2016 at 11:23 AM, Zachary Turner <zturner at google.com>
> wrote:
>> Unfortunately the proposal here doesn't get rid of process creation, it
>> just changes the process being created from a GnuWin32 one to one that we
>> write ourselves.  Happy to entertain suggestions for how to get rid of
>> process creation entirely, but it doesn't seem simple to me.
>> On Tue, Aug 16, 2016 at 11:20 AM Yaron Keren <yaron.keren at gmail.com>
>> wrote:
>>> You can use msys2 rather than gnuwin32.
>>> Nevertheless it would be great to get rid of this dependency, as well as
>>> speedup the regressions tests. Process creation is slower on Windows than
>>> Linux and so the tests run much slower.
>>> 2016-08-16 21:14 GMT+03:00 Zachary Turner via llvm-dev <
>>> llvm-dev at lists.llvm.org>:
>>>> That's more like a workaround though.  The real problem is that file
>>>> deletion is racy on Windows.  I can't count the number of times I've
>>>> encountered this error, only to find out that adding a retry fixed the
>>>> problem.  Sure, if you can remove opened files then there's no problem to
>>>> begin with, but even if you can't, you can still remove the file by
>>>> retrying again 100ms later or so.  It seems silly to disable a test which
>>>> could be testing useful functionality because of some quirk of an OS.
>>>> If you had your own robust rm command, it can retry a few times,
>>>> allowing the test to run everywhere.
>>>> On Tue, Aug 16, 2016 at 11:07 AM Reid Kleckner via llvm-dev <
>>>> llvm-dev at lists.llvm.org> wrote:
>>>>> On Tue, Aug 16, 2016 at 10:09 AM, Greg Bedwell via llvm-dev <
>>>>> llvm-dev at lists.llvm.org> wrote:
>>>>>> Anecdotally, most of the times I've seen people add "REQUIRES: shell"
>>>>>>> on
>>>>>>> a test they really meant "disable on windows". I think/hope that's
>>>>>>> usually temporary while they investigate problems, but it might
>>>>>>> explain
>>>>>>> why so many tests say they require shell when they don't.
>>>>>> In at least one case I can think of
>>>>>> ("clang/test/Format/style-on-command-line.cpp") the "REQUIRES: shell" is
>>>>>> there to work around annoying intermittent failures on Windows where 'rm'
>>>>>> was failing with permission denied errors just occasionally enough to be a
>>>>>> problem.  I've definitely seen this happen in a number of other places
>>>>>> previously although I can't think whether this affects any other lit tests
>>>>>> off-hand, but I know that personally I've had to implement 'robust rm'
>>>>>> (basically, keep on trying until the error goes away on its own) on Windows
>>>>>> in a number of different systems to work around this sort of problem
>>>>>> before.  Replacing gnuwin32 with something where we could easily implement
>>>>>> something like 'robust <cmd>' versions for Windows when we encounter these
>>>>>> sorts of issues would be fantastic, so I'm definitely in favour of removing
>>>>>> the dependency.
>>>>> You can use "REQUIRES: can-remove-opened-file" to express this
>>>>> requirement more precisely.
>>>>> _______________________________________________
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