[M3devel] formsedit crash during startup sometimes?

[Jay]

I don't know yet.
I just know that it happens before and after switching to "new small unix/*.i3 files", so not that.
 
 
I'm away for a few days with only an x86 laptop, I might get around to testing something in a virtual machine, see if repros. Otherwise it'll wait a bit.
 
 
Soon I will probably resort to going back to 5.4.0 or something, verifying no repro, then do "time bisection" or whatever you call it ("binary search"?) -- jump ahead some chunk of time, ideally half way between then and now, see if it repros, jump forward or backward half again depending on if it repros, etc..
 
 
Wouldn't it be super cool, though if I could just issue one command, wait overnight or whatever, and voila, several of those builds done, in both directions, just awaiting human test/observation? Yeah..
 
 
I don't even know how yet to sync an entire CVS tree to a date yet, maybe cvs upd -d?
(Nice thing about 5.4.0 is I don't need CVS to identify it.)
 
 
I also need to ensure that the non-repro case hits the line in question and if so..well, what I'd really love to do, but not sure how viable it is, is write code within the running system (before it runs), to set a hardware breakpoint on the appropriate address, for each appropriate address as the data types are created, and just have dump core when it hits. I wasn't able to get it to even repro in debugger for SOLgnu. I'll try PPC_DARWIN in a debugger, but even if it repros I'm a bit pessimistic on tracking it down.
 
Bisection while tedious and slow should definitely converge on the answer.
 
 
 - Jay


________________________________
> CC: m3devel at elegosoft.com
> From: hosking at cs.purdue.edu
> To: jay.krell at cornell.edu
> Subject: Re: [M3devel] formsedit crash during startup sometimes?
> Date: Thu, 19 Mar 2009 22:07:56 +1100
>
> This is a new bug. What changes introduced it?
>
> On 19 Mar 2009, at 21:22, Jay wrote:
>
> RTHooks__CheckLoadTracedRef is I'm sure innocent. It gets called before any pointer deref, I guess. The problem is the pointer is sometimes null, sometimes not. And why that is is what we need to figure out.
>
> - Jay
>
>
>> From: jay.krell at cornell.edu
>> To: m3devel at elegosoft.com
>> Date: Thu, 19 Mar 2009 07:47:47 +0000
>> Subject: [M3devel] formsedit crash during startup sometimes?
>>
>>
>> Formsedit on SOLgnu also crashes, sometimes, during startup.
>> It doesn't seem to crash in a debugger, but you can load up the core dump after a crash. It looks very similar as on PPC_DARWIN.
>>
>>
>> In both cases, it is dereferencing the value 4, just after calling RTHooks__CheckLoadTracedRef? Relevant? Coincidence?
>>
>>
>> -bash-3.00$ uname -a
>> SunOS unknown 5.10 Generic_118833-17 sun4u sparc SUNW,Sun-Blade-100
>> -bash-3.00$ rm core
>> -bash-3.00$ ./formsedit
>> Segmentation Fault (core dumped)
>> -bash-3.00$ dbx ./formsedit ./core
>> ...
>> t at 2 (l at 2) terminated by signal KILL (Killed)
>> 0xfe3c03d0: ___nanosleep+0x0008: bcc,a,pt %icc,___nanosleep+0x18 ! 0xfe3c03e0
>> (dbx) lwps
>> l at 1 LWP suspended in lwp_yield()
>>>l at 2 LWP suspended in ___nanosleep()
>> l at 3 LWP suspended in __lwp_park()
>> l at 4 LWP suspended in ___nanosleep()
>> l at 11 LWP suspended in __lwp_park()
>> l at 12 LWP suspended in __lwp_park()
>> l at 13 LWP suspended in __lwp_park()
>> o l at 27 signal SIGSEGV in ScrollerVBTClass__PaintViewWithShadows()
>> l at 28 LWP suspended in __lwp_park()
>> (dbx) lwp l at 27
>> t at 27 (l at 27) stopped in ScrollerVBTClass__PaintViewWithShadows at 0xff1b945c
>> 0xff1b945c: ScrollerVBTClass__PaintViewWithShadows+0x0340: ld [%g1], %g1
>> (dbx) dis $pc - 0x10
>> dbx: warning: unknown language, 'c' assumed
>> 0xff1b941c: ScrollerVBTClass__PaintViewWithShadows+0x0300: inc -4, %g1
>> 0xff1b9420: ScrollerVBTClass__PaintViewWithShadows+0x0304: ld [%g1], %g1
>> 0xff1b9424: ScrollerVBTClass__PaintViewWithShadows+0x0308: sll %g1, 22, %g1
>> 0xff1b9428: ScrollerVBTClass__PaintViewWithShadows+0x030c: srl %g1, 31, %g1
>> 0xff1b942c: ScrollerVBTClass__PaintViewWithShadows+0x0310: btog 1, %g1
>> 0xff1b9430: ScrollerVBTClass__PaintViewWithShadows+0x0314: and %g1, 255, %g1
>> 0xff1b9434: ScrollerVBTClass__PaintViewWithShadows+0x0318: cmp %g1, 0
>> 0xff1b9438: ScrollerVBTClass__PaintViewWithShadows+0x031c: bne,pt %icc,ScrollerVBTClass__Pain
>> tViewWithShadows+0x334 ! 0xff1b9450
>> 0xff1b943c: ScrollerVBTClass__PaintViewWithShadows+0x0320: nop
>> 0xff1b9440: ScrollerVBTClass__PaintViewWithShadows+0x0324: ld [%fp - 24], %g1
>> (dbx) dis
>> 0xff1b9444: ScrollerVBTClass__PaintViewWithShadows+0x0328: mov %g1, %o0
>> 0xff1b9448: ScrollerVBTClass__PaintViewWithShadows+0x032c: call RTHooks__CheckLoadTracedRef
>> [PLT] ! 0xff2a9518
>> 0xff1b944c: ScrollerVBTClass__PaintViewWithShadows+0x0330: nop
>> 0xff1b9450: ScrollerVBTClass__PaintViewWithShadows+0x0334: ld [%fp + 68], %g3
>> 0xff1b9454: ScrollerVBTClass__PaintViewWithShadows+0x0338: ld [%fp - 24], %g1
>> 0xff1b9458: ScrollerVBTClass__PaintViewWithShadows+0x033c: inc 4, %g1
>> 0xff1b945c: ScrollerVBTClass__PaintViewWithShadows+0x0340: ld [%g1], %g1
>> 0xff1b9460: ScrollerVBTClass__PaintViewWithShadows+0x0344: st %g1, [%fp - 180]
>> 0xff1b9464: ScrollerVBTClass__PaintViewWithShadows+0x0348: add %fp, -40, %g1
>> 0xff1b9468: ScrollerVBTClass__PaintViewWithShadows+0x034c: add %fp, -180, %g2
>> (dbx) print $g1
>> $g1 = 4ULL
>> (dbx)
>>
>> I believe it is on the last line of the function, the PaintTint call (due to what PPC_DARWIN showed).
>>
>>
>> PROCEDURE PaintViewWithShadows (v: T) =
>> VAR
>> dom : Rect.T;
>> stripe: Rect.T;
>> r : Rect.T;
>> f : Rect.Partition;
>> BEGIN
>> dom := VBT.Domain(v);
>> stripe := ComputeStripe(v, dom);
>> (* Paint the scroll. We are careful not to draw the area of the
>> trough that will be covered by the stripe. This helps reduce
>> the flicker. *)
>> r := Rect.Inset(dom, v.shadowPixels);
>> ShadowPaint.Border(v, Region.Full, v.shadow, Shadow.Style.Lowered,
>> r, dom);
>> Rect.Factor(r, stripe, f, 0, 0);
>> FOR i := FIRST(f) TO LAST(f) DO
>> IF i # 2 AND NOT Rect.IsEmpty(f[i]) THEN
>> VBT.PaintTint(v, f[i], v.troughColor);
>> END;
>> END;
>> (* Paint the stripe. *)
>> r := Rect.Inset(stripe, v.shadowPixels);
>> ShadowPaint.Border(v, Region.Full, v.shadow, Shadow.Style.Raised,
>> r, stripe);
>> VBT.PaintTint(v, r, v.shadow.bg);
>> END PaintViewWithShadows;
>>
>>
>> I'm somewhat just showing people how to get started debugging it, in case folks are as afraid of command line debuggers as I used to be.
>>
>>
>> - Jay
>