Re: Thematic Crash - hard to debug

[Fred Kiefer]

The lines that the debugger reports look like this:



if ([[img image] size].width > 64
        || [[img image] size].height > 64)

The most likely reason for a crash here is [img image] being nil. Just add a 
check for this condition a few lines above and see what happens.

Hope this helps,
Fred

> Am 16.12.2020 um 16:56 schrieb Riccardo Mottola <riccardo.mottola@libero.it>:
> 
> Hello,
> 
> I am suffering a crash im Thematic as soon as I open the image inspector
> of the theme. It happens on NetBSD/x86-32 with the gcc runtime.
> - I am unable to get the libobjc2 runtime working on NetBSD yet, so no
> comparison
> - on Linux, both 32bit and 64bit, gcc or libobjc2 runtime I do not have
> the issue nor does running valgrind show any useful result
> - valgrind is not available on NetBSD
> 
> I get this if compiled with -O2
> 
> Program received signal SIGSEGV, Segmentation fault.
> 0xae562bde in objc_msg_lookup () from /usr/lib/libobjc.so.4
> (gdb) bt
> #0  0xae562bde in objc_msg_lookup () from /usr/lib/libobjc.so.4
> #1  0x08055402 in -[ImagesView refreshCells] (self=<optimized out>,
>     _cmd=0x8058f6f <-[ImageElement initWithView:owner:]+10162>) at
> ImageElement.m:354
> #2  0xab02c110 in ?? ()
> Backtrace stopped: previous frame inner to this frame (corrupt stack?)
> 
> I compiled all GNUstep core in debug mode without -O2, but that doesn't
> help getting a better stacktrace, but no help.
> If I compile Thematic without -O2, I get no crash!
> 
> Thus I suppose there is a memory error which gets hidden without
> optimization (addign lots of data can hide off-by one errors or such)
> and that it is in Thematic but not in gnustep base/gui.
> 
> I tried compiling then -O1 and I think I finally obtain a useful stacktrace:
> 
> Program received signal SIGSEGV, Segmentation fault.
> 0xacc13be4 in objc_msg_lookup () from /usr/lib/libobjc.so.4
> (gdb) bt
> 
> 
> #0  0xb6cbdbe4 in objc_msg_lookup () from /usr/lib/libobjc.so.4
> #1  0x08055467 in -[ImagesView refreshCells] (self=0x8054ef9
> <-[ImagesView addObject:]+158>,
>     _cmd=0xb3787290) at ImageElement.m:348
> #2  0x08073248 in _OBJC_SELECTOR_TABLE ()
> #3  0x08054ef9 in -[ImagesView addObject:] (self=0xb3787290,
>     _cmd=0x8073330 <_OBJC_SELECTOR_TABLE+1136>, anObject=0xb2686100) at
> ImageElement.m:172
> #4  0x08058fa1 in -[ImageElement initWithView:owner:] (self=<optimized
> out>,
>     _cmd=0x806fc98 <_OBJC_SELECTOR_TABLE+1368>, aView=0xb380e410,
> aDocument=0xb28260f0)
>     at ImageElement.m:544
> #5  0x0804d5d3 in -[ThemeDocument elementForView:] (self=0xb28260f0,
>     _cmd=0x806fbf0 <_OBJC_SELECTOR_TABLE+1200>, aView=0xb380e410) at
> ThemeDocument.m:472
> #6  0x0804b86b in -[ThemeDocument changeSelection:at:] (self=0xb28260f0,
>     _cmd=0x806fb60 <_OBJC_SELECTOR_TABLE+1056>, aView=0xb380e410,
> mousePoint=...)
>     at ThemeDocument.m:316
> #7  0x0804d113 in -[ThemeDocumentView mouseDown:] (self=0xb2731b70,
>     _cmd=0xb7789150 <_OBJC_SELECTOR_TABLE+3568>, theEvent=0xb27e67d0) at
> ThemeDocument.m:207
> #8  0xb753bf2f in -[NSWindow sendEvent:] (self=0xb26fba10,
>     _cmd=0xb76b3cd0 <_OBJC_SELECTOR_TABLE+2448>, theEvent=0xb27e67d0) at
> NSWindow.m:4154
> #9  0xb7334d22 in -[NSApplication sendEvent:] (self=0xb3710e10,
>     _cmd=0xb76b3c08 <_OBJC_SELECTOR_TABLE+2248>, theEvent=0xb27e67d0) at
> NSApplication.m:2148
> #10 0xb733336c in -[NSApplication run] (self=0xb3710e10, _cmd=0xb76a67c8
> <_OBJC_SELECTOR_TABLE+936>)
>     at NSApplication.m:1585
> #11 0xb730f48d in NSApplicationMain (argc=argc@entry=1,
> argv=argv@entry=0xbfb336c8) at Functions.m:123
> #12 0x0806592e in gnustep_base_user_main (argc=1, argv=0xbfb336c8) at
> main.m:31
> #13 0xb6ef431f in main (argc=1, argv=0xbfb336c8, env=0xbfb336d0) at
> NSProcessInfo.m:1008
> #14 0x0804a056 in ___start ()
> #15 0x08049d87 in _start ()
> 
> I set NSZombieEnabled=YES but I get a crash anyway! usually that should
> save from such situations?
> 
> Riccardo
>