[llvm] r296253 - [DebugInfo] Skip implicit_const attributes when dumping .debug_info. NFC.

[Victor Leschuk via llvm-commits]

Also readelf does print flag_present in .debug_info, but doesn't print 
implicit_const. (Support for DWARFv5 was merged into GNU binutils master 
few days ago).


On 02/27/2017 09:29 PM, Victor Leschuk via llvm-commits wrote:
>
> I think flag_present and implicit_const attributes shouldn't be 
> treated as similar here: flag_present attributes physically do have a 
> record in .debug_info section, while implicit_const attributes are not 
> physically mentioned there.  Printing implicit_const values when 
> dumping .debug_info can be more convenient for reader but it will 
> actually violate the definition of dump. When dumping section contents 
> we expect to see what is actually there, don't we?
>
>
> On 02/27/2017 09:04 PM, David Blaikie wrote:
>>
>>
>> On Mon, Feb 27, 2017 at 10:00 AM Victor Leschuk 
>> <vleschuk at accesssoftek.com <mailto:vleschuk at accesssoftek.com>> wrote:
>>
>>
>>
>>     On 02/27/2017 08:04 PM, David Blaikie wrote:
>>>     Skipping these values doesn't seem to be correct - in the case
>>>     of flag_present, I think the value is still rendered in the
>>>     dump, is it not?
>>     Do you mean that the value is somehow mentioned in .debug_info
>>     section? It is not.
>>
>>
>> Looks to me like it is:
>>
>> dumping debug info for this code: void f1() { }
>>
>> produces this:
>>
>>   .debug_abbrev contents:
>>   ...
>>   [2] DW_TAG_subprogram DW_CHILDREN_no
>>           ...
>>           DW_AT_external  DW_FORM_flag_present
>>
>>   .debug_info contents:
>>   ...
>>   0x0000002a:   DW_TAG_subprogram [2]
>>                   ...
>>                   DW_AT_external [DW_FORM_flag_present] (true)
>>
>> I would expect similar behavior for const_value - that the attribute 
>> and its constant value is printed in the debug_info dump.
>>
>>
>>>     I would expect the same for implicit_const values. (also, this
>>>     needs test coverage either way)
>>     Yes, you are correct. I will create tests when we decide what's
>>     right behavior here.
>>
>>     I think skipping is correct here: we are dumping .debug_info data
>>     based on attributes stored in AbbrevDecl, this code was based on
>>     assumption that every attribute has representation in .debug_info
>>     section, that was before implicit_const form was introduced.
>>
>>>
>>>     On Sat, Feb 25, 2017 at 5:27 AM Victor Leschuk via llvm-commits
>>>     <llvm-commits at lists.llvm.org
>>>     <mailto:llvm-commits at lists.llvm.org>> wrote:
>>>
>>>         Author: vleschuk
>>>         Date: Sat Feb 25 07:15:57 2017
>>>         New Revision: 296253
>>>
>>>         URL: http://llvm.org/viewvc/llvm-project?rev=296253&view=rev
>>>         Log:
>>>         [DebugInfo] Skip implicit_const attributes when dumping
>>>         .debug_info. NFC.
>>>
>>>         When dumping .debug_info section we loop through all
>>>         attributes mentioned in
>>>         .debug_abbrev section and dump values using
>>>         DWARFFormValue::extractValue().
>>>         We need to skip implicit_const attributes here as their
>>>         values are not
>>>         really located in .debug_info but directly in .debug_abbrev.
>>>         This patch fixes
>>>         triggered assert() in DWARFFormValue::extractValue() caused
>>>         by trying to
>>>         access implicit_const values from .debug_info.
>>>
>>>         Modified:
>>>             llvm/trunk/lib/DebugInfo/DWARF/DWARFDie.cpp
>>>
>>>         Modified: llvm/trunk/lib/DebugInfo/DWARF/DWARFDie.cpp
>>>         URL:
>>>         http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/DebugInfo/DWARF/DWARFDie.cpp?rev=296253&r1=296252&r2=296253&view=diff
>>>         ==============================================================================
>>>         --- llvm/trunk/lib/DebugInfo/DWARF/DWARFDie.cpp (original)
>>>         +++ llvm/trunk/lib/DebugInfo/DWARF/DWARFDie.cpp Sat Feb 25
>>>         07:15:57 2017
>>>         @@ -329,6 +329,12 @@ void DWARFDie::dump(raw_ostream &OS, uns
>>>
>>>                  // Dump all data in the DIE for the attributes.
>>>                  for (const auto &AttrSpec : AbbrevDecl->attributes()) {
>>>         +          if (AttrSpec.Form == DW_FORM_implicit_const) {
>>>         +            // We are dumping .debug_info section ,
>>>         +            // implicit_const attribute values are not
>>>         really stored here,
>>>         +            // but in .debug_abbrev section. So we just
>>>         skip such attrs.
>>>         +            continue;
>>>         +          }
>>>                    dumpAttribute(OS, *this, &offset, AttrSpec.Attr,
>>>         AttrSpec.Form,
>>>                                  Indent);
>>>                  }
>>>
>>>
>>>         _______________________________________________
>>>         llvm-commits mailing list
>>>         llvm-commits at lists.llvm.org <mailto:llvm-commits at lists.llvm.org>
>>>         http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-commits
>>>
>>
>>     -- 
>>     Best Regards,
>>     Victor
>>
>
> -- 
> Best Regards,
> Victor
>
>
> _______________________________________________
> llvm-commits mailing list
> llvm-commits at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-commits

-- 
Best Regards,
Victor

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20170227/35951555/attachment.html>