[lldb-dev] lldb crash while debugging wxWidgets application that was built with g++

[Eran Ifrah]

On Wed, Apr 9, 2014 at 12:11 AM, Greg Clayton <gclayton at apple.com> wrote:

> This is a serious problem with the debug info that GCC and Clang recently
> started to emit to try and save space by omitting important debug info.
>
> The problem is:
>
> class A : public B
> {
> }
>
> The debug info for "A" is complete, but since no one used stuff from class
> "B" they decided to just forward declare "B". Why is this a problem?
> Because we are trying to reconstruct a class definition of "A" using
> incomplete information.
>
> There are two things that can fix this:
> 1 - Modify the DWARF parser to look for a complete version of "B"
> elsewhere in the current executable's debug info (but there might not be
> one).
> 2 - Change flags to GCC to have it not elide this debug info (don't know
> what these flags would be, you will need to find out if there is such a
> flag).
> 3 - Just start and complete the definition for "B" and pretend it is a
> class that contains nothing
>
> Solution #1 is might alleviate some of the problems, but often will result
> in a failure when there is no complete definition of "B".
>
> Solution #2 is the best solution, but this doesn't mean that people won't
> run into this crasher when debugging random code.
>
> Solution #3 is dangerous because you might have foo.cpp whose debug info
> has complete definitions for A and B, and bar.cpp that has a complete
> definition for A but not for B. Then you write and expression that uses an
> instance of "A" from foo.cpp and uses it with an instance of "A" from
> bar.cpp and the expression parser will now complain that is has two
> competing definitions for class "A" that don't match.
>
> Solution #1 should probably be tried first. If you can send me the
> executable you were debugging with debug info inside it, I can look and see
> if solution #1 will fix your current problem. We should avoid crashing,
> that is for sure.
>
> This  might be a slight problem since I was trying to debug codelite.
With debug symbols it can go up to 200MB and it consists of way too many
shared libraries
Let me first to try and narrowing it to something minimalistic


Greg
>
> On Apr 8, 2014, at 1:49 PM, Eran Ifrah <eran.ifrah at gmail.com> wrote:
>
> > Hi,
> >
> > While debugging a real world application (codelite) I placed a
> breakpoint in the 'OnAbout' function
> > attempting to view any of the local variables resulted in crash, see
> below:
> >
> > Process 24146 stopped
> > * thread #1: tid = 24146, 0x00000000006667f6
> codelite`clMainFrame::OnAbout(this=0x000000000215f5c0,
> (null)=0x00007fffa6fd2640) + 66 at frame.cpp:1794, name = 'codelite', stop
> reason = step over
> >     frame #0: 0x00000000006667f6
> codelite`clMainFrame::OnAbout(this=0x000000000215f5c0,
> (null)=0x00007fffa6fd2640) + 66 at frame.cpp:1794
> >    1791     wxString mainTitle;
> >    1792     mainTitle = CODELITE_VERSION_STR;
> >    1793
> > -> 1794     AboutDlg dlg(this, mainTitle);
> >    1795     dlg.SetInfo(mainTitle);
> >    1796     dlg.ShowModal();
> >    1797 }
> > (lldb) p dlg
> > error: libwx_gtk2u_unofficial_core-3.0.so.0 DWARF DIE at 0x030ac4cc for
> class 'wxSizer' has a base class 'wxClientDataContainer' that is a forward
> declaration, not a complete definition.
> > Please file a bug against the compiler and include the preprocessed
> output for
> /home/david/devel/packages/wx/3.0-2/wxwidgets3.0-3.0.0/objs_gtk_sh/../src/common/sizer.cpp
> > Segmentation fault
> >
> > From the segfault message, I understand that this is a bug with gcc
> > Still, is there a way to suppress this error by telling lldb to silently
> ignore this? ( I prefer it to display nothing instead of crashing and
> taking down codelite with it )
> >
> > Thanks
> >
> > --
> > Eran Ifrah
> > Author of codelite, a cross platform open source C/C++ IDE:
> http://www.codelite.org
> > wxCrafter, a wxWidgets RAD: http://wxcrafter.codelite.org
> > _______________________________________________
> > lldb-dev mailing list
> > lldb-dev at cs.uiuc.edu
> > http://lists.cs.uiuc.edu/mailman/listinfo/lldb-dev
>
>


-- 
Eran Ifrah
Author of codelite, a cross platform open source C/C++ IDE:
http://www.codelite.org
wxCrafter, a wxWidgets RAD: http://wxcrafter.codelite.org
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