Refactor rangelist handling to prepare for dwarf5 .debug_rngslist

Dwarf5 introduces a new .debug_rngslist section, to take the place
of the Dwarf4 .debug_ranges. However, the dwarf version is CU-based,
and not file-based, so there can be both sections, and which section
the CU needs isn't known until the dwarf parser encounters either
DW_AT_ranges (dwarf 4 and lower) or DW_AT_rnglists_base (dwarf 5).

This change refactors the code around range lists and range list
readers to defer the decision of what section to parse until
the relevant attribute is found. It moves the range list section
reader from the range-list handler itself (which doesn't know which
section it will use) to the CU context, and then lets the handler
know when it encounters DW_AT_ranges.

I will add a reader for the new dwarf5 section, along with the code to
interpret the new section, and its forms and such in a subsequent patch.

Change-Id: Ie92e4c9daa3f0acb98d7ef74f6b9c2065db849b1
Reviewed-on: https://chromium-review.googlesource.com/c/breakpad/breakpad/+/2433684
Reviewed-by: Mark Mentovai <mark@chromium.org>

1 files changed, 8 insertions, 16 deletions

diff --git a/src/common/linux/dump_symbols.cc b/src/common/linux/dump_symbols.cc
index 8ecf0bc4..ac2559cd 100644
--- a/src/common/linux/dump_symbols.cc
+++ b/src/common/linux/dump_symbols.cc
@@ -232,23 +232,14 @@ bool LoadStabs(const typename ElfClass::Ehdr* elf_header,
 // owned by a function) with the results.
 class DumperRangesHandler : public DwarfCUToModule::RangesHandler {
  public:
-  DumperRangesHandler(const uint8_t* buffer, uint64_t size,
-                      dwarf2reader::ByteReader* reader)
-      : buffer_(buffer), size_(size), reader_(reader) { }
+  DumperRangesHandler() { }
 
   bool ReadRanges(uint64_t offset, Module::Address base_address,
                   vector<Module::Range>* ranges) {
     DwarfRangeListHandler handler(base_address, ranges);
-    dwarf2reader::RangeListReader rangelist_reader(buffer_, size_, reader_,
-                                                   &handler);
 
-    return rangelist_reader.ReadRangeList(offset);
+    return reader_->ReadRangeList(offset, &handler);
   }
-
- private:
-  const uint8_t* buffer_;
-  uint64_t size_;
-  dwarf2reader::ByteReader* reader_;
 };
 
 // A line-to-module loader that accepts line number info parsed by
@@ -314,17 +305,18 @@ bool LoadDwarf(const string& dwarf_filename,
   }
 
   // Optional .debug_ranges reader
-  scoped_ptr<DumperRangesHandler> ranges_handler;
   dwarf2reader::SectionMap::const_iterator ranges_entry =
       file_context.section_map().find(".debug_ranges");
   if (ranges_entry != file_context.section_map().end()) {
     const std::pair<const uint8_t*, uint64_t>& ranges_section =
       ranges_entry->second;
-    ranges_handler.reset(
-      new DumperRangesHandler(ranges_section.first, ranges_section.second,
-                              &byte_reader));
+    file_context.SetDebugRangeInfo(ranges_section.first,
+                                   ranges_section.second,
+                                   &byte_reader);
   }
 
+  DumperRangesHandler ranges_handler;
+
   // Parse all the compilation units in the .debug_info section.
   DumperLineToModule line_to_module(&byte_reader);
   dwarf2reader::SectionMap::const_iterator debug_info_entry =
@@ -341,7 +333,7 @@ bool LoadDwarf(const string& dwarf_filename,
     // data that was found.
     DwarfCUToModule::WarningReporter reporter(dwarf_filename, offset);
     DwarfCUToModule root_handler(&file_context, &line_to_module,
-                                 ranges_handler.get(), &reporter);
+                                 &ranges_handler, &reporter);
     // Make a Dwarf2Handler that drives the DIEHandler.
     dwarf2reader::DIEDispatcher die_dispatcher(&root_handler);
     // Make a DWARF parser for the compilation unit at OFFSET.