[DWARFLinker] Prefix debug section names with '.' in the comments. NFC.

[RamNalamothu]

Summary

In DWARFLinker.h, some comments prefix the debug section names
with '.' while others do not.

[avl]

I think it would be better to not add any prefixes to section names. On Darwin, section names have "__" prefix. So using "." looks a bit incompatible. It seems, it is better always use section names without prefixes.

[RamNalamothu]

In D108519#2959080, @avl wrote:

I think it would be better to not add any prefixes to section names. On Darwin, section names have "__" prefix. So using "." looks a bit incompatible. It seems, it is better always use section names without prefixes.

But this file implements DWARF support and the DWARF spec specified section names are prefixed with '.'.

In any case, I think the comments can be consistent in all the places on whether or not prefix debug section names with '.'.
Currently section names prefixed with '.' in some places and not prefixed with '.' in the rest.

[dblaikie]

In D108519#2959080, @avl wrote:

I think it would be better to not add any prefixes to section names. On Darwin, section names have "__" prefix. So using "." looks a bit incompatible. It seems, it is better always use section names without prefixes.

Given the DWARF spec talks about the names in the ELF form (with the leading dot) and various other parts of LLVM do this - including messages in llvm-dwarfdump --verify, for instance - I think it's probably not bad to standardize on the dot forms when referring to these names. (the MachO forms also get abbreviated in some places, which would get a bit more weird).

[avl]

In D108519#2959097, @RamNalamothu wrote:

In D108519#2959080, @avl wrote:

I think it would be better to not add any prefixes to section names. On Darwin, section names have "__" prefix. So using "." looks a bit incompatible. It seems, it is better always use section names without prefixes.

But this file implements DWARF support and the DWARF spec specified section names are prefixed with '.'.

In any case, I think the comments can be consistent in all the places on whether or not prefix debug section names with '.'.
Currently section names prefixed with '.' in some places and not prefixed with '.' in the rest.

Right. Comments need to be consistent in all places. Avoiding prefixes would make names looking good for all platforms. But if the idea is to be conformant with Dwarf spec and others prefer dot form I am OK with it also.

[RamNalamothu]

If there are no concerns on standardizing the DWARF section names on the dot forms, can somebody approve these changes?

[dblaikie]

Sounds good

llvm/include/llvm/DWARFLinker/DWARFLinker.h

public:
   /// Checks that the specified DIE has a DW_AT_Low_pc attribute
   /// that references into a live code section.
   ///
   /// \returns true and sets Info.InDebugMap if it is the case.
   virtual bool hasLiveAddressRange(const DWARFDie &DIE,
                                    CompileUnit::DIEInfo &Info) = 0;
 
   /// Apply the valid relocations to the buffer \p Data, taking into
-  /// account that Data is at \p BaseOffset in the debug_info section.
+  /// account that Data is at \p BaseOffset in the .debug_info section.
   ///
   /// \returns true whether any reloc has been applied.
   virtual bool applyValidRelocs(MutableArrayRef<char> Data, uint64_t BaseOffset,
                                 bool IsLittleEndian) = 0;
 
   /// Relocate the given address offset if a valid relocation exists.
   virtual llvm::Expected<uint64_t> relocateIndexedAddr(uint64_t StartOffset,
                                                        uint64_t EndOffset) = 0;
public:
   virtual ~DwarfEmitter();
 
   /// Emit DIE containing warnings.
   virtual void emitPaperTrailWarningsDie(DIE &Die) = 0;
 
   /// Emit section named SecName with data SecData.
   virtual void emitSectionContents(StringRef SecData, StringRef SecName) = 0;
 
-  /// Emit the abbreviation table \p Abbrevs to the debug_abbrev section.
+  /// Emit the abbreviation table \p Abbrevs to the .debug_abbrev section.
   virtual void
   emitAbbrevs(const std::vector<std::unique_ptr<DIEAbbrev>> &Abbrevs,
               unsigned DwarfVersion) = 0;
 
   /// Emit the string table described by \p Pool.
   virtual void emitStrings(const NonRelocatableStringpool &Pool) = 0;
 
   /// Emit DWARF debug names.
public:
   /// Emit Apple Objective-C accelerator table.
   virtual void
   emitAppleObjc(AccelTable<AppleAccelTableStaticOffsetData> &Table) = 0;
 
   /// Emit Apple type accelerator table.
   virtual void
   emitAppleTypes(AccelTable<AppleAccelTableStaticTypeData> &Table) = 0;
 
-  /// Emit debug_ranges for \p FuncRange by translating the
+  /// Emit .debug_ranges for \p FuncRange by translating the
   /// original \p Entries.
   virtual void emitRangesEntries(
       int64_t UnitPcOffset, uint64_t OrigLowPc,
       const FunctionIntervals::const_iterator &FuncRange,
       const std::vector<DWARFDebugRangeList::RangeListEntry> &Entries,
       unsigned AddressSize) = 0;
 
-  /// Emit debug_aranges entries for \p Unit and if \p DoRangesSection is true,
-  /// also emit the debug_ranges entries for the DW_TAG_compile_unit's
+  /// Emit .debug_aranges entries for \p Unit and if \p DoRangesSection is true,
+  /// also emit the .debug_ranges entries for the DW_TAG_compile_unit's
   /// DW_AT_ranges attribute.
   virtual void emitUnitRangesEntries(CompileUnit &Unit,
                                      bool DoRangesSection) = 0;
 
-  /// Copy the debug_line over to the updated binary while unobfuscating the
+  /// Copy the .debug_line over to the updated binary while unobfuscating the
   /// file names and directories.
   virtual void translateLineTable(DataExtractor LineData, uint64_t Offset) = 0;
 
-  /// Emit the line table described in \p Rows into the debug_line section.
+  /// Emit the line table described in \p Rows into the .debug_line section.
   virtual void emitLineTableForUnit(MCDwarfLineTableParams Params,
                                     StringRef PrologueBytes,
                                     unsigned MinInstLength,
                                     std::vector<DWARFDebugLine::Row> &Rows,
                                     unsigned AdddressSize) = 0;
 
   /// Emit the .debug_pubnames contribution for \p Unit.
   virtual void emitPubNamesForUnit(const CompileUnit &Unit) = 0;
 
   /// Emit the .debug_pubtypes contribution for \p Unit.
   virtual void emitPubTypesForUnit(const CompileUnit &Unit) = 0;
 
   /// Emit a CIE.
   virtual void emitCIE(StringRef CIEBytes) = 0;
 
   /// Emit an FDE with data \p Bytes.
   virtual void emitFDE(uint32_t CIEOffset, uint32_t AddreSize, uint32_t Address,
                        StringRef Bytes) = 0;
 
-  /// Emit the debug_loc contribution for \p Unit by copying the entries from
+  /// Emit the .debug_loc contribution for \p Unit by copying the entries from
   /// \p Dwarf and offsetting them. Update the location attributes to point to
   /// the new entries.
   virtual void emitLocationsForUnit(
       const CompileUnit &Unit, DWARFContext &Dwarf,
       std::function<void(StringRef, SmallVectorImpl<uint8_t> &)>
           ProcessExpr) = 0;
 
   /// Emit the compilation unit header for \p Unit in the
-  /// debug_info section.
+  /// .debug_info section.
   ///
   /// As a side effect, this also switches the current Dwarf version
   /// of the MC layer to the one of U.getOrigUnit().
   virtual void emitCompileUnitHeader(CompileUnit &Unit,
                                      unsigned DwarfVersion) = 0;
 
   /// Recursively emit the DIE tree rooted at \p Die.
   virtual void emitDIE(DIE &Die) = 0;
private:
     void addObjCAccelerator(CompileUnit &Unit, const DIE *Die,
                             DwarfStringPoolEntryRef Name,
                             OffsetsStringPool &StringPool, bool SkipPubSection);
   };
 
   /// Assign an abbreviation number to \p Abbrev
   void assignAbbrev(DIEAbbrev &Abbrev);
 
-  /// Compute and emit debug_ranges section for \p Unit, and
+  /// Compute and emit .debug_ranges section for \p Unit, and
   /// patch the attributes referencing it.
   void patchRangesForUnit(const CompileUnit &Unit, DWARFContext &Dwarf,
                           const DWARFFile &File) const;
 
   /// Generate and emit the DW_AT_ranges attribute for a compile_unit if it had
   /// one.
   void generateUnitRanges(CompileUnit &Unit) const;
 
   /// Extract the line tables from the original dwarf, extract the relevant
   /// parts according to the linked function ranges and emit the result in the
-  /// debug_line section.
+  /// .debug_line section.
   void patchLineTableForUnit(CompileUnit &Unit, DWARFContext &OrigDwarf,
                              const DWARFFile &File);
 
   /// Emit the accelerator entries for \p Unit.
   void emitAcceleratorEntriesForUnit(CompileUnit &Unit);
   void emitDwarfAcceleratorEntriesForUnit(CompileUnit &Unit);
   void emitAppleAcceleratorEntriesForUnit(CompileUnit &Unit);
   void emitPubAcceleratorEntriesForUnit(CompileUnit &Unit);
private:
   bool AtLeastOneDwarfAccelTable = false;
 
   /// The CIEs that have been emitted in the output section. The actual CIE
   /// data serves a the key to this StringMap, this takes care of comparing the
   /// semantics of CIEs defined in different object files.
   StringMap<uint32_t> EmittedCIEs;
 
   /// Offset of the last CIE that has been emitted in the output
-  /// debug_frame section.
+  /// .debug_frame section.
   uint32_t LastCIEOffset = 0;
 
   /// Apple accelerator tables.
   AccelTable<DWARF5AccelTableStaticData> DebugNames;
   AccelTable<AppleAccelTableStaticOffsetData> AppleNames;
   AccelTable<AppleAccelTableStaticOffsetData> AppleNamespaces;
   AccelTable<AppleAccelTableStaticOffsetData> AppleObjc;
   AccelTable<AppleAccelTableStaticTypeData> AppleTypes;