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.
Greg
On Apr 8, 2014, at 1:49 PM, Eran Ifrah <[email protected]> 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
> [email protected]
> http://lists.cs.uiuc.edu/mailman/listinfo/lldb-dev
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