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

[Nicolas Cellier]

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

>
> Stef
>
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