[lldb-dev] PATCH for REVIEW - Fix [Bug 15038] LLDB does not support printing wide-character variables on Linux

[Enrico Granata]

Hi Ashok,
thanks for submitting an LLDB patch :)

I have looked at the code and while I see where the patch is coming from, I see a potential issue with it.

The code in ReadUTFBufferAndDumpToStream, which is what you are editing, is meant to work on a partial string (i.e. one that does not have a NULL terminator at the end). The reason for that is that you might have a wstring that is 1GB long and we would not want to try and read all of it and then display it. What we do is pick a size and only extract that much data. For obvious reasons, your string might be longer than our upper boundary, so you would get a chunk of valid bytes and then no end-of-buffer marker.

It looks like your code would fail in that case and produce no summary for a string if an EIO was received before \0.

Is there any reason why you can’t just check if (error == EIO and data_read > 0) and if so treat this as a “partial string” condition and keep going?
Would that break/crash anything?

Best,
Enrico Granata
✉ egranata@.com
✆ 27683

On Mar 27, 2013, at 2:52 PM, "Thirumurthi, Ashok" <ashok.thirumurthi at intel.com> wrote:

> The root cause for Bug 15038 is a ptrace EIO that can occur because we don't know the size of a (UTF) string and so read a fixed number of characters for strings.  The attached fix accepts EIO in the case where data has been read and a null terminator of the correct size and alignment was found.
> 
> - Ashok
> 
> -----Original Message-----
> From: lldb-dev-bounces at cs.uiuc.edu [mailto:lldb-dev-bounces at cs.uiuc.edu] On Behalf Ofbugzilla-daemon at llvm.org
> Sent: Tuesday, January 22, 2013 10:13 AM
> To: lldb-dev at cs.uiuc.edu
> Subject: [lldb-dev] [Bug 15038] New: LLDB does not support printing wide-character variables on Linux
> 
> http://llvm.org/bugs/show_bug.cgi?id=15038
> 
>             Bug #: 15038
>           Summary: LLDB does not support printing wide-character
>                    variables on Linux
>           Product: lldb
>           Version: unspecified
>          Platform: PC
>        OS/Version: Linux
>            Status: NEW
>          Severity: enhancement
>          Priority: P
>         Component: All Bugs
>        AssignedTo: lldb-dev at cs.uiuc.edu
>        ReportedBy: daniel.malea at intel.com
>    Classification: Unclassified
> 
> 
> Printing a variable of wchar_t type does not behave as expected and results in garbage being printed on the screen.
> 
> To reproduce, remove the @expectedFailureLinux decorator from TestChar1632T.py and TestCxxWCharT.py and run:
> 
> python dotest.py --executable <path-to-lldb> lang/cpp/char1632_t lang/cpp/wchar_t
> 
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