This revision was automatically updated to reflect the committed changes.
Closed by commit rLLDB360874: DWARFContext: Return empty data extractors 
instead of null pointers (authored by labath, committed by ).
Herald added a project: LLDB.

Changed prior to commit:
  https://reviews.llvm.org/D61942?vs=199597&id=199787#toc

Repository:
  rLLDB LLDB

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D61942/new/

https://reviews.llvm.org/D61942

Files:
  lit/SymbolFile/DWARF/debug_aranges-empty-section.s
  source/Plugins/SymbolFile/DWARF/DWARFContext.cpp
  source/Plugins/SymbolFile/DWARF/DWARFContext.h
  source/Plugins/SymbolFile/DWARF/DWARFDebugAranges.cpp
  source/Plugins/SymbolFile/DWARF/DWARFDebugInfo.cpp

Index: source/Plugins/SymbolFile/DWARF/DWARFDebugAranges.cpp
===================================================================
--- source/Plugins/SymbolFile/DWARF/DWARFDebugAranges.cpp
+++ source/Plugins/SymbolFile/DWARF/DWARFDebugAranges.cpp
@@ -42,8 +42,6 @@
 // Extract
 llvm::Error
 DWARFDebugAranges::extract(const DWARFDataExtractor &debug_aranges_data) {
-  assert(debug_aranges_data.ValidOffset(0));
-
   lldb::offset_t offset = 0;
 
   DWARFDebugArangeSet set;
@@ -65,8 +63,8 @@
       }
     }
     set.Clear();
-    }
-    return llvm::ErrorSuccess();
+  }
+  return llvm::ErrorSuccess();
 }
 
 void DWARFDebugAranges::Dump(Log *log) const {
Index: source/Plugins/SymbolFile/DWARF/DWARFDebugInfo.cpp
===================================================================
--- source/Plugins/SymbolFile/DWARF/DWARFDebugInfo.cpp
+++ source/Plugins/SymbolFile/DWARF/DWARFDebugInfo.cpp
@@ -44,13 +44,10 @@
   assert(m_dwarf2Data);
 
   m_cu_aranges_up = llvm::make_unique<DWARFDebugAranges>();
-  const DWARFDataExtractor *debug_aranges_data =
+  const DWARFDataExtractor &debug_aranges_data =
       m_context.getOrLoadArangesData();
-  if (debug_aranges_data) {
-    llvm::Error error = m_cu_aranges_up->extract(*debug_aranges_data);
-    if (error)
-      return std::move(error);
-  }
+  if (llvm::Error error = m_cu_aranges_up->extract(debug_aranges_data))
+    return std::move(error);
 
   // Make a list of all CUs represented by the arange data in the file.
   std::set<dw_offset_t> cus_with_data;
Index: source/Plugins/SymbolFile/DWARF/DWARFContext.cpp
===================================================================
--- source/Plugins/SymbolFile/DWARF/DWARFContext.cpp
+++ source/Plugins/SymbolFile/DWARF/DWARFContext.cpp
@@ -13,31 +13,32 @@
 using namespace lldb;
 using namespace lldb_private;
 
-static const DWARFDataExtractor *
-LoadOrGetSection(Module &module, SectionType section_type,
-                 llvm::Optional<DWARFDataExtractor> &extractor) {
-  if (extractor.hasValue())
-    return extractor->GetByteSize() > 0 ? extractor.getPointer() : nullptr;
-
-  // Initialize to an empty extractor so that we always take the fast path going
-  // forward.
-  extractor.emplace();
-
-  const SectionList *section_list = module.GetSectionList();
+static DWARFDataExtractor LoadSection(Module &module,
+                                      SectionType section_type) {
+  SectionList *section_list = module.GetSectionList();
   if (!section_list)
-    return nullptr;
+    return DWARFDataExtractor();
 
   auto section_sp = section_list->FindSectionByType(section_type, true);
   if (!section_sp)
-    return nullptr;
+    return DWARFDataExtractor();
 
-  section_sp->GetSectionData(*extractor);
-  return extractor.getPointer();
+  DWARFDataExtractor data;
+  section_sp->GetSectionData(data);
+  return data;
+}
+
+static const DWARFDataExtractor &
+LoadOrGetSection(Module &module, SectionType section_type,
+                 llvm::Optional<DWARFDataExtractor> &extractor) {
+  if (!extractor)
+    extractor = LoadSection(module, section_type);
+  return *extractor;
 }
 
 DWARFContext::DWARFContext(Module &module) : m_module(module) {}
 
-const DWARFDataExtractor *DWARFContext::getOrLoadArangesData() {
+const DWARFDataExtractor &DWARFContext::getOrLoadArangesData() {
   return LoadOrGetSection(m_module, eSectionTypeDWARFDebugAranges,
                           m_data_debug_aranges);
 }
Index: source/Plugins/SymbolFile/DWARF/DWARFContext.h
===================================================================
--- source/Plugins/SymbolFile/DWARF/DWARFContext.h
+++ source/Plugins/SymbolFile/DWARF/DWARFContext.h
@@ -23,7 +23,7 @@
 public:
   explicit DWARFContext(Module &module);
 
-  const DWARFDataExtractor *getOrLoadArangesData();
+  const DWARFDataExtractor &getOrLoadArangesData();
 };
 } // namespace lldb_private
 
Index: lit/SymbolFile/DWARF/debug_aranges-empty-section.s
===================================================================
--- lit/SymbolFile/DWARF/debug_aranges-empty-section.s
+++ lit/SymbolFile/DWARF/debug_aranges-empty-section.s
@@ -0,0 +1,63 @@
+# Test that an empty .debug_aranges section doesn't confuse (or crash) us.
+
+# RUN: llvm-mc %s -triple x86_64-pc-linux -filetype=obj >%t
+# RUN: lldb %t -o "breakpoint set -n f" -b | FileCheck %s
+
+# CHECK: Breakpoint 1: where = {{.*}}`f, address = 0x0000000000000047
+
+	.text
+	.globl	f                       # -- Begin function f
+	.type	f,@function
+        .rept 0x47
+        nop
+        .endr
+f:                                      # @f
+.Lfunc_begin0:
+	retq
+.Lfunc_end0:
+	.size	f, .Lfunc_end0-f
+                                        # -- End function
+	.section	.debug_str,"MS",@progbits,1
+.Linfo_string3:
+	.asciz	"f"                     # string offset=83
+	.section	.debug_abbrev,"",@progbits
+	.byte	1                       # Abbreviation Code
+	.byte	17                      # DW_TAG_compile_unit
+	.byte	1                       # DW_CHILDREN_yes
+	.byte	17                      # DW_AT_low_pc
+	.byte	1                       # DW_FORM_addr
+	.byte	18                      # DW_AT_high_pc
+	.byte	6                       # DW_FORM_data4
+	.byte	0                       # EOM(1)
+	.byte	0                       # EOM(2)
+	.byte	2                       # Abbreviation Code
+	.byte	46                      # DW_TAG_subprogram
+	.byte	0                       # DW_CHILDREN_no
+	.byte	17                      # DW_AT_low_pc
+	.byte	1                       # DW_FORM_addr
+	.byte	18                      # DW_AT_high_pc
+	.byte	6                       # DW_FORM_data4
+	.byte	3                       # DW_AT_name
+	.byte	14                      # DW_FORM_strp
+	.byte	0                       # EOM(1)
+	.byte	0                       # EOM(2)
+	.byte	0                       # EOM(3)
+	.section	.debug_info,"",@progbits
+.Lcu_begin0:
+	.long	.Ldebug_info_end0-.Ldebug_info_start0 # Length of Unit
+.Ldebug_info_start0:
+	.short	4                       # DWARF version number
+	.long	.debug_abbrev           # Offset Into Abbrev. Section
+	.byte	8                       # Address Size (in bytes)
+	.byte	1                       # Abbrev [1] 0xb:0x35 DW_TAG_compile_unit
+	.quad	.Lfunc_begin0           # DW_AT_low_pc
+	.long	.Lfunc_end0-.Lfunc_begin0 # DW_AT_high_pc
+	.byte	2                       # Abbrev [2] 0x2a:0x15 DW_TAG_subprogram
+	.quad	.Lfunc_begin0           # DW_AT_low_pc
+	.long	.Lfunc_end0-.Lfunc_begin0 # DW_AT_high_pc
+	.long	.Linfo_string3          # DW_AT_name
+	.byte	0                       # End Of Children Mark
+.Ldebug_info_end0:
+
+	.section	".note.GNU-stack","",@progbits
+	.section	.debug_aranges,"",@progbits
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