R 4.0.2 64-bit Windows hangs

On 8/25/20 6:14 PM, Tomas Kalibera wrote:

On 8/22/20 9:33 PM, Jeroen Ooms wrote:

On Sat, Aug 22, 2020 at 9:10 PM Tomas Kalibera
<tomas.kalibera at gmail.com> wrote:

On 8/22/20 8:26 PM, Tomas Kalibera wrote:

On 8/22/20 7:58 PM, Jeroen Ooms wrote:

On Sat, Aug 22, 2020 at 8:39 AM Tomas Kalibera
<tomas.kalibera at gmail.com> wrote:

On 8/21/20 11:45 PM, m19tdn+9alxwj7d2bmk--- via R-devel wrote:

Ah yes, this is related. I reported v2010 below, but it looks like
I was updated to this Insider Build overnight without my knowledge,
and conflated it with the new installation R v4 this morning.

I will continue to look into the issue with the methods Tomas
mentioned.

It is interesting that a rare 5 years old problem would re-appear on
current Insider builds. Which build of Windows are you running
exactly?
I've seen another report about a crash on 20190.1000. It'd be
nice to
know if it is present also in newer builds, i.e. in 20197.

I installed the latest 20197 build in a vm, and I can indeed
reproduce
this problem.

What seems to be happening is that R triggers an infinite
recursion in
Windows unwinding mechanism, and eventually dies with a stack
overflow. Attached a backtrace of the initial 100 frames of the main
thread (the pattern in the top ~30 frames continues forever).

The microsoft blog doesn't mention anything related to exception
handling has changed in recent versions:
https://docs.microsoft.com/en-us/windows-insider/at-home/active-dev-branch

Thanks, unfortunately that does not ring any bells (except below), I
can't guess from this what is the underlying cause of the problem.
There may be something wrong in how we use setjmp/longjmp or how
setjmp/longjmp works on Windows.

It reminds me of a problem I've been debugging few days ago, when
longjump implementation segfaults on Windows 10 (recent but not
Insider build) probably soon after unwinding the stack, but only with
GCC 10 / MinGW 7 and only in one of the no-segfault tests, and only
with -03 (not -O2, not with with -O3 -fno-split-loops). The problem
was sensitive to these optimization options interestingly on the call
site of long jump (do_abs), even when it was not an immediate caller
of the longjump. I've not tracked this down yet, it will require
looking at the assembly level, and I was suspecting a compiler error
causing the compiler to generate code that messes with the stack or
registers in a way that impacts the upcoming jump. But now as we have
this other problem with setjmp/logjmp, the compiler may not be the top
suspect anymore.

I may not be able to work on this in the next few days or a week, so
if anyone gets there first, please let me know what you find out.

Btw could you please try out if the UCRT build of R crashes as well in
the Insider Windows build ?

Yes, it hangs in exactly the same way, except that the backtrace shows

  ucrtbase!.intrinsic_setjmpex () from C:\WINDOWS\System32\ucrtbase.dll

Instead of msvcrt!_setjmpex (as expected of course).

Thanks. I found what is causing the problem I observed with
GCC10/stock Windows 10, I expect this is the same one as in the
Insider build.
I will investigate further,

Tomas

It seems the problem is between MinGW-W64 and Windows, and really it
causes both the reported crashes in an Insider build (I tested in 20197)
and in my GCC 10 builds in a single "no-segfault" test. setjmp is
implemented using Windows call _setjmpex, which has a second argument
argument, which is set differently by MinGW based on GCC version. When I
set this argument as MinGW-W64 did on early versions of GCC,
mingw_getsp(), it fixes/hides the problems on my systems. Perl5 uses a
similar workaround, but otherwise there is no solid base (documentation,
specification, etc) I am aware of for this change, so this may take some
more time to be properly fixed. Still, if anyone experiments with this
workaround and finds a problem, please let me know. In particular, I am
curious whether it works on earlier versions of Windows (at least with
check-all, including recommended packages).