[Vm-dev] A new ready-to-crash image is available

[Nicolas Cellier]

Le sam. 8 févr. 2020 à 21:45, Nicolas Cellier <
nicolas.cellier.aka.nice at gmail.com> a écrit :

>
>
> Le sam. 8 févr. 2020 à 01:35, Stéphane Rollandin <lecteur at zogotounga.net>
> a écrit :
>
>>
>> > Why only with fast VM? It might be yet another case of Undefined
>> > Behavior (UB)...
>> > I have thus recompiled the VM with UB sanitizer, and there is indeed
>> > some UB reported:
>> >
>> > ../../platforms/Cross/plugins/Squeak3D/b3dMain.c:1252:29: runtime
>> error:
>> > left shift of negative value -760
>> > ../../platforms/Cross/plugins/Squeak3D/b3dMain.c:1254:25: runtime
>> error:
>> > left shift of negative value -751
>> > ../../platforms/Cross/plugins/Squeak3D/b3dDraw.c:317:33: runtime error:
>> > left shift of negative value -802
>> > ../../platforms/Cross/plugins/Squeak3D/b3dDraw.c:318:33: runtime error:
>> > left shift of negative value -802
>> > ../../platforms/Cross/plugins/Squeak3D/b3dDraw.c:316:33: runtime error:
>> > left shift of negative value -114
>> > ../../platforms/Cross/plugins/Squeak3D/b3dMain.c:829:61: runtime error:
>> > left shift of negative value -2
>> >
>> > Though, the instrumented fast VM does not fail...
>> > It might be that some aggressive optimizations assuming the absence of
>> > UB do not occur with all the instrumentation stuff embedded...
>>
>> This is very dark magic.
>>
>> > IMO, declaring a left shift of negative int UB is sort of FOOLISH.
>>
>> Tell me where to vote and I'll vote for you.
>>
>> You cannot yet vote for opinions, except on some social networks ;)
>
> > We will have to protect each and every left shift in b3d with a cast...
>>
>> To see a good side in this, stumbling at this point upon this kind of
>> errors must mean the 3D code in itself is quite sound. Indeed I had only
>> a couple of similar crashes for hours of testing (well, playing).
>>
>> What I saw also a couple times, and which is more difficult to report,
>> is the VM hanging at 100% CPU on its core and having to be killed
>> externally. Could it be the same nasal demons at work?
>>
>> hard to say...
> I think that you can send a SIGUSR1 to dump stacks, or attach a debugger
> to running VM....
>
> Unfortunately, I also had another crash:
>
> ../../platforms/Cross/plugins/Squeak3D/b3dMain.c:954:43: runtime error:
> member access within null pointer of type 'B3DPrimitiveFace' (aka 'struct
> B3DPrimitiveFace')
>
> Segmentation fault Sat Feb  8 21:19:37 2020
>
> VM: 202002050212 nicolas at MBP-de-Nicolas
> :Smalltalk/OpenSmalltalk/opensmalltalk-vm
> Date: Tue Feb 4 18:12:07 2020 CommitHash: 0f974af6a
> Plugins: 202002050212 nicolas at MBP-de-Nicolas
> :Smalltalk/OpenSmalltalk/opensmalltalk-vm
>
> C stack backtrace & registers:
> eax 0x00000018 ebx 0x00000000 ecx 0x040835a8 edx 0x00000000
> edi 0x040835a8 esi 0x040835a8 ebp 0xbfeec978 esp 0xbfeec940
> eip 0x0f0584b5
> 0   Squeak3D                            0x0f0584b5 b3dAddFrontFill + 118
> 1   Squeak                              0x00275ea4 reportStackState + 870
> 2   Squeak                              0x00276862 sigsegv + 353
> 3   libsystem_platform.dylib            0xa7dffbae _sigtramp + 46
> 4   ???                                 0xffffffff 0x0 + 4294967295
> 5   Squeak3D                            0x0f05a0ee b3dToggleTopFills + 604
> 6   Squeak3D                            0x0f05cdc0 b3dMainLoop + 7239
> 7   Squeak3D                            0x0f017adb b3dStartRasterizer +
> 1668
>

And I see that this one more closely match your crash.dmp report...
So the negativeInt<<shift was another problem created by my clang version
on OSX.
I ran a few times without crash, so thought it was thru, but your crash is
not yet fixed...


>> Stef
>>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.squeakfoundation.org/pipermail/vm-dev/attachments/20200208/5bf2b3f3/attachment.html>