[M3devel] formsedit crash during startup sometimes?

[Tony Hosking]

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

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