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

[David Blaikie via llvm-commits]

On Mon, Feb 27, 2017 at 10:00 AM Victor Leschuk <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> 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);
>          }
>
>
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>
> --
> Best Regards,
> Victor
>
>
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