[PATCH] Remove wild .debug_aranges entries generated from unimportant labels

[Richard Mitton]

How would I go about reproducing this bug? I'd really like to see a test 
case.

Richard Mitton
richard at codersnotes.com

On 10/02/2013 07:10 AM, Alexey Samsonov wrote:
> Hi echristo,
>
> r191052 added emitting .debug_aranges to Clang, but this
> functionality is broken: it uses all MC labels added in DWARF Asm
> printer, including the labels for build relocations between
> different DWARF sections, like .Lsection_line or .Ldebug_loc0.
>
> As a result, if any DIE .debug_info would contain "DW_AT_location=0x123"
> attribute, .debug_aranges would also contain a range starting from 0x123,
> breaking tools that rely on this section.
>
> I'm not sure this is the correct fix, please take a look.
>
> http://llvm-reviews.chandlerc.com/D1809
>
> Files:
>    lib/CodeGen/AsmPrinter/DwarfDebug.cpp
>    lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
>    lib/CodeGen/AsmPrinter/DwarfDebug.h
>
> Index: lib/CodeGen/AsmPrinter/DwarfDebug.cpp
> ===================================================================
> --- lib/CodeGen/AsmPrinter/DwarfDebug.cpp
> +++ lib/CodeGen/AsmPrinter/DwarfDebug.cpp
> @@ -1110,8 +1110,8 @@
>   
>   void DwarfDebug::endSections() {
>      // Filter labels by section.
> -  for (size_t n = 0; n < Labels.size(); n++) {
> -    const SymbolCU &SCU = Labels[n];
> +  for (size_t n = 0; n < ArangeLabels.size(); n++) {
> +    const SymbolCU &SCU = ArangeLabels[n];
>       if (SCU.Sym->isInSection()) {
>         // Make a note of this symbol and it's section.
>         const MCSection *Section = &SCU.Sym->getSection();
> @@ -1138,10 +1138,7 @@
>       }
>   
>       // Insert a final terminator.
> -    SymbolCU Entry;
> -    Entry.CU = NULL;
> -    Entry.Sym = Sym;
> -    SectionMap[Section].push_back(Entry);
> +    SectionMap[Section].push_back(SymbolCU(NULL, Sym));
>     }
>   }
>   
> Index: lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
> ===================================================================
> --- lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
> +++ lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
> @@ -181,26 +181,15 @@
>                              const MCSymbol *Label) {
>     DIEValue *Value = new (DIEValueAllocator) DIELabel(Label);
>     Die->addValue(Attribute, Form, Value);
> -
> -  SymbolCU Entry;
> -  Entry.CU = this;
> -  Entry.Sym = Label;
> -
> -  DD->addLabel(Entry);
>   }
>   
>   /// addLabelAddress - Add a dwarf label attribute data and value using
>   /// DW_FORM_addr or DW_FORM_GNU_addr_index.
>   ///
>   void CompileUnit::addLabelAddress(DIE *Die, uint16_t Attribute,
>                                     MCSymbol *Label) {
> -  if (Label) {
> -    SymbolCU Entry;
> -    Entry.CU = this;
> -    Entry.Sym = Label;
> -
> -    DD->addLabel(Entry);
> -  }
> +  if (Label)
> +    DD->addArangeLabel(SymbolCU(this, Label));
>   
>     if (!DD->useSplitDwarf()) {
>       if (Label != NULL) {
> @@ -221,6 +210,7 @@
>   /// form given and an op of either DW_FORM_addr or DW_FORM_GNU_addr_index.
>   ///
>   void CompileUnit::addOpAddress(DIE *Die, const MCSymbol *Sym) {
> +  DD->addArangeLabel(SymbolCU(this, Sym));
>     if (!DD->useSplitDwarf()) {
>       addUInt(Die, 0, dwarf::DW_FORM_data1, dwarf::DW_OP_addr);
>       addLabel(Die, 0, dwarf::DW_FORM_udata, Sym);
> Index: lib/CodeGen/AsmPrinter/DwarfDebug.h
> ===================================================================
> --- lib/CodeGen/AsmPrinter/DwarfDebug.h
> +++ lib/CodeGen/AsmPrinter/DwarfDebug.h
> @@ -303,6 +303,7 @@
>   
>   /// \brief Helper used to pair up a symbol and it's DWARF compile unit.
>   struct SymbolCU {
> +  SymbolCU(CompileUnit *CU, const MCSymbol *Sym) : Sym(Sym), CU(CU) {}
>     const MCSymbol *Sym;
>     CompileUnit *CU;
>   };
> @@ -363,8 +364,8 @@
>     // separated by a zero byte, mapped to a unique id.
>     StringMap<unsigned, BumpPtrAllocator&> SourceIdMap;
>   
> -  // List of all labels used in the output.
> -  std::vector<SymbolCU> Labels;
> +  // List of all labels used in aranges generation.
> +  std::vector<SymbolCU> ArangeLabels;
>   
>     // Size of each symbol emitted (for those symbols that have a specific size).
>     DenseMap <const MCSymbol *, uint64_t> SymSize;
> @@ -731,7 +732,7 @@
>     void addTypeUnitType(DIE *Die) { TypeUnits.push_back(Die); }
>   
>     /// \brief Add a label so that arange data can be generated for it.
> -  void addLabel(SymbolCU SCU) { Labels.push_back(SCU); }
> +  void addArangeLabel(SymbolCU SCU) { ArangeLabels.push_back(SCU); }
>   
>     /// \brief For symbols that have a size designated (e.g. common symbols),
>     /// this tracks that size.