[PATCH] D40156: Fix recursive attribute fetching in DWARFDie

[Greg Clayton via llvm-commits]

Don't ask me. I just have a GCC generated file that does this.

> On Nov 16, 2017, at 4:05 PM, David Blaikie <dblaikie at gmail.com> wrote:
> 
> I don't quite follow - why would there be two levels of abstract origin? (X -abstract_origin-> Y -abstract_origin-> Z) rather than having X refer to Z as its abstract_origin directly?
> 
> On Thu, Nov 16, 2017 at 4:01 PM Greg Clayton via Phabricator <reviews at reviews.llvm.org <mailto:reviews at reviews.llvm.org>> wrote:
> clayborg created this revision.
> Herald added a subscriber: JDevlieghere.
> 
> The previous implementation would only look 1 DW_AT_specification or DW_AT_abstract_origin deep. This means DWARFDie::getName() would fail in certain cases. I ran into such a case while creating a tool that used the LLVM DWARF parser to generate a symbolication format so I have seen this in the wild.
> 
> 
> Repository:
>   rL LLVM
> 
> https://reviews.llvm.org/D40156 <https://reviews.llvm.org/D40156>
> 
> Files:
>   lib/DebugInfo/DWARF/DWARFDie.cpp
>   unittests/DebugInfo/DWARF/DWARFDebugInfoTest.cpp
> 
> 
> Index: unittests/DebugInfo/DWARF/DWARFDebugInfoTest.cpp
> ===================================================================
> --- unittests/DebugInfo/DWARF/DWARFDebugInfoTest.cpp
> +++ unittests/DebugInfo/DWARF/DWARFDebugInfoTest.cpp
> @@ -1287,12 +1287,16 @@
>      auto CUDie = CU.getUnitDIE();
>      auto FuncSpecDie = CUDie.addChild(DW_TAG_subprogram);
>      auto FuncAbsDie = CUDie.addChild(DW_TAG_subprogram);
> +    // Put the linkage name in a second abstract origin DIE to ensure we
> +    // recurse through more than just one DIE when looking for attributes.
> +    auto FuncAbsDie2 = CUDie.addChild(DW_TAG_subprogram);
>      auto FuncDie = CUDie.addChild(DW_TAG_subprogram);
>      auto VarAbsDie = CUDie.addChild(DW_TAG_variable);
>      auto VarDie = CUDie.addChild(DW_TAG_variable);
>      FuncSpecDie.addAttribute(DW_AT_name, DW_FORM_strp, SpecDieName);
> -    FuncAbsDie.addAttribute(DW_AT_linkage_name, DW_FORM_strp, SpecLinkageName);
> +    FuncAbsDie2.addAttribute(DW_AT_linkage_name, DW_FORM_strp, SpecLinkageName);
>      FuncAbsDie.addAttribute(DW_AT_specification, DW_FORM_ref4, FuncSpecDie);
> +    FuncAbsDie.addAttribute(DW_AT_abstract_origin, DW_FORM_ref4, FuncAbsDie2);
>      FuncDie.addAttribute(DW_AT_abstract_origin, DW_FORM_ref4, FuncAbsDie);
>      VarAbsDie.addAttribute(DW_AT_name, DW_FORM_strp, AbsDieName);
>      VarDie.addAttribute(DW_AT_abstract_origin, DW_FORM_ref4, VarAbsDie);
> @@ -1314,7 +1318,8 @@
> 
>    auto FuncSpecDie = CUDie.getFirstChild();
>    auto FuncAbsDie = FuncSpecDie.getSibling();
> -  auto FuncDie = FuncAbsDie.getSibling();
> +  auto FuncAbsDie2 = FuncAbsDie.getSibling();
> +  auto FuncDie = FuncAbsDie2.getSibling();
>    auto VarAbsDie = FuncDie.getSibling();
>    auto VarDie = VarAbsDie.getSibling();
> 
> Index: lib/DebugInfo/DWARF/DWARFDie.cpp
> ===================================================================
> --- lib/DebugInfo/DWARF/DWARFDie.cpp
> +++ lib/DebugInfo/DWARF/DWARFDie.cpp
> @@ -298,17 +298,16 @@
>  DWARFDie::findRecursively(ArrayRef<dwarf::Attribute> Attrs) const {
>    if (!isValid())
>      return None;
> -  auto Die = *this;
> -  if (auto Value = Die.find(Attrs))
> +  if (auto Value = find(Attrs))
>      return Value;
> -  if (auto D = Die.getAttributeValueAsReferencedDie(DW_AT_abstract_origin))
> -    Die = D;
> -  if (auto Value = Die.find(Attrs))
> -    return Value;
> -  if (auto D = Die.getAttributeValueAsReferencedDie(DW_AT_specification))
> -    Die = D;
> -  if (auto Value = Die.find(Attrs))
> -    return Value;
> +  if (auto Die = getAttributeValueAsReferencedDie(DW_AT_abstract_origin)) {
> +    if (auto Value = Die.findRecursively(Attrs))
> +      return Value;
> +  }
> +  if (auto Die = getAttributeValueAsReferencedDie(DW_AT_specification)) {
> +    if (auto Value = Die.findRecursively(Attrs))
> +      return Value;
> +  }
>    return None;
>  }
> 
> 
> 

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