[Vm-dev] Sign-bit bug in character literals > 16r7FFF ... related to SistaV1?

Wed Mar 9 07:38:43 UTC 2022

Hi Nicolas --

There is a bug in the EncoderForSistaV1. The behavior is okay for EncoderForV3PlusClosures. We can discuss this on squeak-dev now, I suppose.

CompiledCode preferredBytecodeSetEncoderClass: EncoderForSistaV1.

CompiledCode preferredBytecodeSetEncoderClass: EncoderForV3PlusClosures.

If you do send #halt instead of #asInteger, you get another interesting debugger when trying to start debugging:

Best,
Marcel
Am 09.03.2022 08:34:11 schrieb Nicolas Cellier <nicolas.cellier.aka.nice at gmail.com>:
Ah OK, I see it on macos too
It remains to determine which operation exactly is involved...
The TextMorph holding the printed result is correct - a WideString, whose
last Character is (Character value: 32768).

Le mer. 9 mars 2022 à 08:08, Marcel Taeumel a
écrit :

>
> Hi Dave, hi Nicolas --
>
> I am working in Windows 10.
>
> > I cannot reproduce on Linux 64 bit either:
> > (Character value: 16r8000) asInteger hex ==> '16r8000'
>
> That's not how you would reproduce it. The bug affects character literals,
> not character objects/instances. You have to evaluate code on that
> character literal.
>
> Maybe this picture helps:
>
>
>
> Best,
> Marcel
>
> Am 08.03.2022 18:56:09 schrieb David T. Lewis :
>
> I cannot reproduce on Linux 64 bit either:
>
> (Character value: 16r8000) asInteger hex ==> '16r8000'
>
> Dave
>
>
> On Tue, Mar 08, 2022 at 06:45:23PM +0100, Nicolas Cellier wrote:
> >
> > Hi Marcel,
> > which OS ?
> > I cannot reproduce on macos 64,
> >
> > Cog[Spur] VM [CoInterpreterPrimitives VMMaker.oscog-eem.3172]
> > 5.20211023.2003
> > Mac OS X built on Mar 6 2022 15:31:16 CET Compiler: 4.2.1 Compatible
> Apple
> > LLVM 10.0.1 (clang-1001.0.46.4)
> > platform sources revision VM: 202110232003
> >
> > Le mar. 8 mars 2022 ?? 17:57, Marcel Taeumel a
> > ??crit :
> >
> > >
> > > Hi Eliot, hi all --
> > >
> > > I think we have an sign-bit bug for character literals with code
> points >
> > > 16r7FFF.
> > >
> > > Steps to reproduce:
> > >
> > > 1. Print it: "Character value: 16r8000"
> > > 2. Inspect the result by evaluating the character literal or send
> > > #asInteger to it. It will most likely not render in a standard Squeak
> and
> > > show up like "$? asInteger".
> > >
> > > In a 32-bit VM, I will get the (positive) integer value 16r3FFF8000.
> > > In a 64-bit VM, I will get the (negative) integer value '-16r8000'.
> > >
> > > Somehow, starting at bit 0, the bits 16 to 29 flip from 0 to 1. In
> 64-bit,
> > > this means a negative number. Not sure about bits 30 and 31 here.
> > >
> > > Is there a bug in the upper tag bits of immediate characters?
> > > Is this related to the 2-byte or 3-byte byte codes in SistaV1?
> > >
> > > Works fine up to 16r7FFF. (This is unrelated to #leadingChar. Mine was
> 0
> > > in this experiment.)
> > >
> > > VM: 202112201228 (VMMaker.oscog-eem.3116)
> > >
> > > Best,
> > > Marcel
> > >
>
>

Ah OK, I see it on macos too

It remains to determine which operation exactly is involved...
The TextMorph holding the printed result is correct - a WideString, whose last Character is (Character value: 32768).

Le mer. 9 mars 2022 à 08:08, Marcel Taeumel <marcel.taeumel at hpi.de [mailto:marcel.taeumel at hpi.de]> a écrit :

Hi Dave, hi Nicolas --

I am working in Windows 10.

> I cannot reproduce on Linux 64 bit either:
> (Character value: 16r8000) asInteger hex ==> '16r8000'

That's not how you would reproduce it. The bug affects character literals, not character objects/instances. You have to evaluate code on that character literal.

Maybe this picture helps:

Best,
Marcel

Am 08.03.2022 18:56:09 schrieb David T. Lewis <lewis at mail.msen.com [mailto:lewis at mail.msen.com]>:

I cannot reproduce on Linux 64 bit either:

(Character value: 16r8000) asInteger hex ==> '16r8000'

Dave

On Tue, Mar 08, 2022 at 06:45:23PM +0100, Nicolas Cellier wrote:
>
> Hi Marcel,
> which OS ?
> I cannot reproduce on macos 64,
>
> Cog[Spur] VM [CoInterpreterPrimitives VMMaker.oscog-eem.3172]
> 5.20211023.2003
> Mac OS X built on Mar 6 2022 15:31:16 CET Compiler: 4.2.1 Compatible Apple
> LLVM 10.0.1 (clang-1001.0.46.4)
> platform sources revision VM: 202110232003
>
> Le mar. 8 mars 2022 ?? 17:57, Marcel Taeumel a
> ??crit :
>
> >
> > Hi Eliot, hi all --
> >
> > I think we have an sign-bit bug for character literals with code points >
> > 16r7FFF.
> >
> > Steps to reproduce:
> >
> > 1. Print it: "Character value: 16r8000"
> > 2. Inspect the result by evaluating the character literal or send
> > #asInteger to it. It will most likely not render in a standard Squeak and
> > show up like "$? asInteger".
> >
> > In a 32-bit VM, I will get the (positive) integer value 16r3FFF8000.
> > In a 64-bit VM, I will get the (negative) integer value '-16r8000'.
> >
> > Somehow, starting at bit 0, the bits 16 to 29 flip from 0 to 1. In 64-bit,
> > this means a negative number. Not sure about bits 30 and 31 here.
> >
> > Is there a bug in the upper tag bits of immediate characters?
> > Is this related to the 2-byte or 3-byte byte codes in SistaV1?
> >
> > Works fine up to 16r7FFF. (This is unrelated to #leadingChar. Mine was 0
> > in this experiment.)
> >
> > VM: 202112201228 (VMMaker.oscog-eem.3116)
> >
> > Best,
> > Marcel
> >

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