[lldb][NFCI] Unify DW_TAG -> string conversions (llvm#90657)

bulbazord · web-flow · commit e2b3e4ea9f2d · 2024-05-03T11:05:11.000-07:00
The high level goal is to have 1 way of converting a DW_TAG value into a
human-readable string.

There are 3 ways this change accomplishes that:
1.) Changing DW_TAG_value_to_name to not create custom error strings.
  The way it was doing this is error-prone: Specifically, it was using a
  function-local static char buffer and handing out a pointer to it.
  Initialization of this is thread-safe, but mutating it is definitely
  not. Multiple threads that want to call this function could step on
  each others toes. The implementation in this patch sidesteps the issue
  by just returning a StringRef with no mention of the tag value in it.
2.) Changing all uses of DW_TAG_value_to_name to log the value of the
  tag since the function doesn't create a string with the value in it
  anymore.
3.) Removing `DWARFBaseDIE::GetTagAsCString()`. Callers should call
  DW_TAG_value_to_name on the tag directly.
diff --git a/lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp b/lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp
@@ -452,9 +452,9 @@ TypeSP DWARFASTParserClang::ParseTypeFromDWARF(const SymbolContext &sc,
         log,
         "DWARFASTParserClang::ParseTypeFromDWARF "
         "(die = {0:x16}, decl_ctx = {1:p} (die "
-        "{2:x16})) {3} name = '{4}')",
+        "{2:x16})) {3} ({4}) name = '{5}')",
         die.GetOffset(), static_cast<void *>(context), context_die.GetOffset(),
-        die.GetTagAsCString(), die.GetName());
+        DW_TAG_value_to_name(die.Tag()), die.Tag(), die.GetName());
   }
 
   Type *type_ptr = dwarf->GetDIEToType().lookup(die.GetDIE());
@@ -765,9 +765,10 @@ DWARFASTParserClang::ParseTypeModifier(const SymbolContext &sc,
           if (log)
             dwarf->GetObjectFile()->GetModule()->LogMessage(
                 log,
-                "SymbolFileDWARF::ParseType (die = {0:x16}) {1} '{2}' "
+                "SymbolFileDWARF::ParseType (die = {0:x16}) {1} ({2}) '{3}' "
                 "is Objective-C 'id' built-in type.",
-                die.GetOffset(), die.GetTagAsCString(), die.GetName());
+                die.GetOffset(), DW_TAG_value_to_name(die.Tag()), die.Tag(),
+                die.GetName());
           clang_type = m_ast.GetBasicType(eBasicTypeObjCID);
           encoding_data_type = Type::eEncodingIsUID;
           attrs.type.Clear();
@@ -776,9 +777,10 @@ DWARFASTParserClang::ParseTypeModifier(const SymbolContext &sc,
           if (log)
             dwarf->GetObjectFile()->GetModule()->LogMessage(
                 log,
-                "SymbolFileDWARF::ParseType (die = {0:x16}) {1} '{2}' "
+                "SymbolFileDWARF::ParseType (die = {0:x16}) {1} ({2}) '{3}' "
                 "is Objective-C 'Class' built-in type.",
-                die.GetOffset(), die.GetTagAsCString(), die.GetName());
+                die.GetOffset(), DW_TAG_value_to_name(die.Tag()), die.Tag(),
+                die.GetName());
           clang_type = m_ast.GetBasicType(eBasicTypeObjCClass);
           encoding_data_type = Type::eEncodingIsUID;
           attrs.type.Clear();
@@ -787,9 +789,10 @@ DWARFASTParserClang::ParseTypeModifier(const SymbolContext &sc,
           if (log)
             dwarf->GetObjectFile()->GetModule()->LogMessage(
                 log,
-                "SymbolFileDWARF::ParseType (die = {0:x16}) {1} '{2}' "
+                "SymbolFileDWARF::ParseType (die = {0:x16}) {1} ({2}) '{3}' "
                 "is Objective-C 'selector' built-in type.",
-                die.GetOffset(), die.GetTagAsCString(), die.GetName());
+                die.GetOffset(), DW_TAG_value_to_name(die.Tag()), die.Tag(),
+                die.GetName());
           clang_type = m_ast.GetBasicType(eBasicTypeObjCSel);
           encoding_data_type = Type::eEncodingIsUID;
           attrs.type.Clear();
@@ -808,10 +811,10 @@ DWARFASTParserClang::ParseTypeModifier(const SymbolContext &sc,
             if (log)
               dwarf->GetObjectFile()->GetModule()->LogMessage(
                   log,
-                  "SymbolFileDWARF::ParseType (die = {0:x16}) {1} "
-                  "'{2}' is 'objc_object*', which we overrode to "
-                  "'id'.",
-                  die.GetOffset(), die.GetTagAsCString(), die.GetName());
+                  "SymbolFileDWARF::ParseType (die = {0:x16}) {1} ({2}) '{3}' "
+                  "is 'objc_object*', which we overrode to 'id'.",
+                  die.GetOffset(), DW_TAG_value_to_name(die.Tag()), die.Tag(),
+                  die.GetName());
             clang_type = m_ast.GetBasicType(eBasicTypeObjCID);
             encoding_data_type = Type::eEncodingIsUID;
             attrs.type.Clear();
@@ -870,10 +873,10 @@ TypeSP DWARFASTParserClang::ParseEnum(const SymbolContext &sc,
       if (log) {
         dwarf->GetObjectFile()->GetModule()->LogMessage(
             log,
-            "SymbolFileDWARF({0:p}) - {1:x16}}: {2} type \"{3}\" is a "
-            "forward declaration, complete type is {4:x8}",
+            "SymbolFileDWARF({0:p}) - {1:x16}}: {2} ({3}) type \"{4}\" is a "
+            "forward declaration, complete type is {5:x8}",
             static_cast<void *>(this), die.GetOffset(),
-            DW_TAG_value_to_name(tag), attrs.name.GetCString(),
+            DW_TAG_value_to_name(tag), tag, attrs.name.GetCString(),
             type_sp->GetID());
       }
 
@@ -1734,11 +1737,10 @@ DWARFASTParserClang::ParseStructureLikeDIE(const SymbolContext &sc,
         if (log) {
           dwarf->GetObjectFile()->GetModule()->LogMessage(
               log,
-              "SymbolFileDWARF({0:p}) - {1:x16}: {2} type "
-              "\"{3}\" is an "
-              "incomplete objc type, complete type is {4:x8}",
+              "SymbolFileDWARF({0:p}) - {1:x16}: {2} ({3}) type \"{4}\" is an "
+              "incomplete objc type, complete type is {5:x8}",
               static_cast<void *>(this), die.GetOffset(),
-              DW_TAG_value_to_name(tag), attrs.name.GetCString(),
+              DW_TAG_value_to_name(tag), tag, attrs.name.GetCString(),
               type_sp->GetID());
         }
 
@@ -1760,10 +1762,10 @@ DWARFASTParserClang::ParseStructureLikeDIE(const SymbolContext &sc,
     if (log) {
       dwarf->GetObjectFile()->GetModule()->LogMessage(
           log,
-          "SymbolFileDWARF({0:p}) - {1:x16}: {2} type \"{3}\" is a "
+          "SymbolFileDWARF({0:p}) - {1:x16}: {2} ({3}) type \"{4}\" is a "
           "forward declaration, trying to find complete type",
           static_cast<void *>(this), die.GetOffset(), DW_TAG_value_to_name(tag),
-          attrs.name.GetCString());
+          tag, attrs.name.GetCString());
     }
 
     // See if the type comes from a Clang module and if so, track down
@@ -1789,10 +1791,10 @@ DWARFASTParserClang::ParseStructureLikeDIE(const SymbolContext &sc,
       if (log) {
         dwarf->GetObjectFile()->GetModule()->LogMessage(
             log,
-            "SymbolFileDWARF({0:p}) - {1:x16}: {2} type \"{3}\" is a "
-            "forward declaration, complete type is {4:x8}",
+            "SymbolFileDWARF({0:p}) - {1:x16}: {2} ({3}) type \"{4}\" is a "
+            "forward declaration, complete type is {5:x8}",
             static_cast<void *>(this), die.GetOffset(),
-            DW_TAG_value_to_name(tag), attrs.name.GetCString(),
+            DW_TAG_value_to_name(tag), tag, attrs.name.GetCString(),
             type_sp->GetID());
       }
 
@@ -1836,10 +1838,10 @@ DWARFASTParserClang::ParseStructureLikeDIE(const SymbolContext &sc,
       if (log) {
         dwarf->GetObjectFile()->GetModule()->LogMessage(
             log,
-            "SymbolFileDWARF({0:p}) - {1:x16}: {2} type \"{3}\" "
+            "SymbolFileDWARF({0:p}) - {1:x16}: {2} ({3}) type \"{4}\" "
             "clang::ClassTemplateDecl failed to return a decl.",
             static_cast<void *>(this), die.GetOffset(),
-            DW_TAG_value_to_name(tag), attrs.name.GetCString());
+            DW_TAG_value_to_name(tag), tag, attrs.name.GetCString());
       }
       return TypeSP();
     }
@@ -3018,11 +3020,11 @@ void DWARFASTParserClang::ParseSingleMember(
               this_field_info.bit_offset)))) {
       ObjectFile *objfile = die.GetDWARF()->GetObjectFile();
       objfile->GetModule()->ReportWarning(
-          "{0:x16}: {1} bitfield named \"{2}\" has invalid "
-          "bit offset ({3:x8}) member will be ignored. Please file a bug "
+          "{0:x16}: {1} ({2}) bitfield named \"{3}\" has invalid "
+          "bit offset ({4:x8}) member will be ignored. Please file a bug "
           "against the "
-          "compiler and include the preprocessed output for {4}\n",
-          die.GetID(), DW_TAG_value_to_name(tag), attrs.name,
+          "compiler and include the preprocessed output for {5}\n",
+          die.GetID(), DW_TAG_value_to_name(tag), tag, attrs.name,
           this_field_info.bit_offset, GetUnitName(parent_die).c_str());
       return;
     }
diff --git a/lldb/source/Plugins/SymbolFile/DWARF/DWARFBaseDIE.cpp b/lldb/source/Plugins/SymbolFile/DWARF/DWARFBaseDIE.cpp
@@ -35,10 +35,6 @@ dw_tag_t DWARFBaseDIE::Tag() const {
     return llvm::dwarf::DW_TAG_null;
 }
 
-const char *DWARFBaseDIE::GetTagAsCString() const {
-  return DW_TAG_value_to_name(Tag());
-}
-
 const char *DWARFBaseDIE::GetAttributeValueAsString(const dw_attr_t attr,
                                                 const char *fail_value) const {
   if (IsValid())
diff --git a/lldb/source/Plugins/SymbolFile/DWARF/DWARFBaseDIE.h b/lldb/source/Plugins/SymbolFile/DWARF/DWARFBaseDIE.h
@@ -85,8 +85,6 @@ class DWARFBaseDIE {
   // Accessing information about a DIE
   dw_tag_t Tag() const;
 
-  const char *GetTagAsCString() const;
-
   dw_offset_t GetOffset() const;
 
   // Get the LLDB user ID for this DIE. This is often just the DIE offset,
diff --git a/lldb/source/Plugins/SymbolFile/DWARF/DWARFDefines.cpp b/lldb/source/Plugins/SymbolFile/DWARF/DWARFDefines.cpp
@@ -15,18 +15,12 @@
 namespace lldb_private::plugin {
 namespace dwarf {
 
-const char *DW_TAG_value_to_name(uint32_t val) {
-  static char invalid[100];
-
-  if (val == 0)
-    return "NULL";
+llvm::StringRef DW_TAG_value_to_name(dw_tag_t tag) {
+  static constexpr llvm::StringLiteral s_unknown_tag_name("<unknown DW_TAG>");
+  if (llvm::StringRef tag_name = llvm::dwarf::TagString(tag); !tag_name.empty())
+    return tag_name;
 
-  llvm::StringRef llvmstr = llvm::dwarf::TagString(val);
-  if (llvmstr.empty()) {
-    snprintf(invalid, sizeof(invalid), "Unknown DW_TAG constant: 0x%x", val);
-    return invalid;
-  }
-  return llvmstr.data();
+  return s_unknown_tag_name;
 }
 
 const char *DW_AT_value_to_name(uint32_t val) {
diff --git a/lldb/source/Plugins/SymbolFile/DWARF/DWARFDefines.h b/lldb/source/Plugins/SymbolFile/DWARF/DWARFDefines.h
@@ -17,7 +17,7 @@ namespace dwarf {
 
 typedef uint32_t DRC_class; // Holds DRC_* class bitfields
 
-const char *DW_TAG_value_to_name(uint32_t val);
+llvm::StringRef DW_TAG_value_to_name(dw_tag_t tag);
 
 const char *DW_AT_value_to_name(uint32_t val);
 
diff --git a/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp b/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp
@@ -1555,8 +1555,10 @@ Type *SymbolFileDWARF::ResolveTypeUID(const DWARFDIE &die,
     Log *log = GetLog(DWARFLog::DebugInfo);
     if (log)
       GetObjectFile()->GetModule()->LogMessage(
-          log, "SymbolFileDWARF::ResolveTypeUID (die = {0:x16}) {1} '{2}'",
-          die.GetOffset(), die.GetTagAsCString(), die.GetName());
+          log,
+          "SymbolFileDWARF::ResolveTypeUID (die = {0:x16}) {1} ({2}) '{3}'",
+          die.GetOffset(), DW_TAG_value_to_name(die.Tag()), die.Tag(),
+          die.GetName());
 
     // We might be coming in in the middle of a type tree (a class within a
     // class, an enum within a class), so parse any needed parent DIEs before
@@ -1572,11 +1574,10 @@ Type *SymbolFileDWARF::ResolveTypeUID(const DWARFDIE &die,
           if (log)
             GetObjectFile()->GetModule()->LogMessage(
                 log,
-                "SymbolFileDWARF::ResolveTypeUID (die = {0:x16}) "
-                "{1} '{2}' "
-                "resolve parent forward type for {3:x16})",
-                die.GetOffset(), die.GetTagAsCString(), die.GetName(),
-                decl_ctx_die.GetOffset());
+                "SymbolFileDWARF::ResolveTypeUID (die = {0:x16}) {1} ({2}) "
+                "'{3}' resolve parent forward type for {4:x16})",
+                die.GetOffset(), DW_TAG_value_to_name(die.Tag()), die.Tag(),
+                die.GetName(), decl_ctx_die.GetOffset());
         } break;
 
         default:
@@ -1644,9 +1645,9 @@ bool SymbolFileDWARF::CompleteType(CompilerType &compiler_type) {
     Log *log = GetLog(DWARFLog::DebugInfo | DWARFLog::TypeCompletion);
     if (log)
       GetObjectFile()->GetModule()->LogMessageVerboseBacktrace(
-          log, "{0:x8}: {1} '{2}' resolving forward declaration...",
-          dwarf_die.GetID(), dwarf_die.GetTagAsCString(),
-          type->GetName().AsCString());
+          log, "{0:x8}: {1} ({2}) '{3}' resolving forward declaration...",
+          dwarf_die.GetID(), DW_TAG_value_to_name(dwarf_die.Tag()),
+          dwarf_die.Tag(), type->GetName().AsCString());
     assert(compiler_type);
     if (DWARFASTParser *dwarf_ast = GetDWARFParser(*dwarf_die.GetCU()))
       return dwarf_ast->CompleteTypeFromDWARF(dwarf_die, type, compiler_type);
@@ -1665,8 +1666,9 @@ Type *SymbolFileDWARF::ResolveType(const DWARFDIE &die,
         return type;
 
       GetObjectFile()->GetModule()->ReportError(
-          "Parsing a die that is being parsed die: {0:x16}: {1} {2}",
-          die.GetOffset(), die.GetTagAsCString(), die.GetName());
+          "Parsing a die that is being parsed die: {0:x16}: {1} ({2}) {3}",
+          die.GetOffset(), DW_TAG_value_to_name(die.Tag()), die.Tag(),
+          die.GetName());
 
     } else
       return type;
@@ -3134,9 +3136,9 @@ SymbolFileDWARF::FindDefinitionTypeForDWARFDeclContext(const DWARFDIE &die) {
     if (log) {
       GetObjectFile()->GetModule()->LogMessage(
           log,
-          "SymbolFileDWARF::FindDefinitionTypeForDWARFDeclContext(tag={0}, "
-          "name='{1}')",
-          DW_TAG_value_to_name(tag), die.GetName());
+          "SymbolFileDWARF::FindDefinitionTypeForDWARFDeclContext(tag={0} "
+          "({1}), name='{2}')",
+          DW_TAG_value_to_name(tag), tag, die.GetName());
     }
 
     // Get the type system that we are looking to find a type for. We will
@@ -3184,10 +3186,10 @@ SymbolFileDWARF::FindDefinitionTypeForDWARFDeclContext(const DWARFDIE &die) {
           GetObjectFile()->GetModule()->LogMessage(
               log,
               "SymbolFileDWARF::"
-              "FindDefinitionTypeForDWARFDeclContext(tag={0}, "
-              "name='{1}') ignoring die={2:x16} ({3})",
-              DW_TAG_value_to_name(tag), die.GetName(), type_die.GetOffset(),
-              type_die.GetName());
+              "FindDefinitionTypeForDWARFDeclContext(tag={0} ({1}), "
+              "name='{2}') ignoring die={3:x16} ({4})",
+              DW_TAG_value_to_name(tag), tag, die.GetName(),
+              type_die.GetOffset(), type_die.GetName());
         }
         return true;
       }
@@ -3197,9 +3199,9 @@ SymbolFileDWARF::FindDefinitionTypeForDWARFDeclContext(const DWARFDIE &die) {
         GetObjectFile()->GetModule()->LogMessage(
             log,
             "SymbolFileDWARF::"
-            "FindDefinitionTypeForDWARFDeclContext(tag={0}, "
-            "name='{1}') trying die={2:x16} ({3})",
-            DW_TAG_value_to_name(tag), die.GetName(), type_die.GetOffset(),
+            "FindDefinitionTypeForDWARFDeclContext(tag={0} ({1}), name='{2}') "
+            "trying die={3:x16} ({4})",
+            DW_TAG_value_to_name(tag), tag, die.GetName(), type_die.GetOffset(),
             type_dwarf_decl_ctx.GetQualifiedName());
       }
 
@@ -3650,8 +3652,8 @@ VariableSP SymbolFileDWARF::ParseVariableDIE(const SymbolContext &sc,
         StreamString strm;
         location->DumpLocation(&strm, eDescriptionLevelFull, nullptr);
         GetObjectFile()->GetModule()->ReportError(
-            "{0:x16}: {1} has an invalid location: {2}", die.GetOffset(),
-            die.GetTagAsCString(), strm.GetData());
+            "{0:x16}: {1} ({2}) has an invalid location: {3}", die.GetOffset(),
+            DW_TAG_value_to_name(die.Tag()), die.Tag(), strm.GetData());
       }
       if (location_DW_OP_addr != LLDB_INVALID_ADDRESS)
         is_static_lifetime = true;
@@ -3839,19 +3841,20 @@ void SymbolFileDWARF::ParseAndAppendGlobalVariable(
       variable_list_sp = sc.comp_unit->GetVariableList(false);
     } else {
       GetObjectFile()->GetModule()->ReportError(
-          "parent {0:x8} {1} with no valid compile unit in "
-          "symbol context for {2:x8} {3}.\n",
-          sc_parent_die.GetID(), sc_parent_die.GetTagAsCString(), die.GetID(),
-          die.GetTagAsCString());
+          "parent {0:x8} {1} ({2}) with no valid compile unit in "
+          "symbol context for {3:x8} {4} ({5}).\n",
+          sc_parent_die.GetID(), DW_TAG_value_to_name(sc_parent_die.Tag()),
+          sc_parent_die.Tag(), die.GetID(), DW_TAG_value_to_name(die.Tag()),
+          die.Tag());
       return;
     }
     break;
 
   default:
     GetObjectFile()->GetModule()->ReportError(
         "didn't find appropriate parent DIE for variable list for {0:x8} "
-        "{1}.\n",
-        die.GetID(), die.GetTagAsCString());
+        "{1} ({2}).\n",
+        die.GetID(), DW_TAG_value_to_name(die.Tag()), die.Tag());
     return;
   }
 
