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 // Copyright (c) 2010 Google Inc.

 // All rights reserved.

 //

 // Redistribution and use in source and binary forms, with or without

 // modification, are permitted provided that the following conditions are

 // met:

 //

 //     * Redistributions of source code must retain the above copyright

 // notice, this list of conditions and the following disclaimer.

 //     * Redistributions in binary form must reproduce the above

 // copyright notice, this list of conditions and the following disclaimer

 // in the documentation and/or other materials provided with the

 // distribution.

 //     * Neither the name of Google Inc. nor the names of its

 // contributors may be used to endorse or promote products derived from

 // this software without specific prior written permission.

 //

 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS

 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT

 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR

 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT

 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,

 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT

 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,

 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY

 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT

 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE

 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

 // Original author: Jim Blandy <jimb@mozilla.com> <jimb@red-bean.com>

 // Implement the DwarfCUToModule class; see dwarf_cu_to_module.h.

 // For <inttypes.h> PRI* macros, before anything else might #include it.

 #ifndef __STDC_FORMAT_MACROS

 #define __STDC_FORMAT_MACROS

 #endif  /* __STDC_FORMAT_MACROS */

 #include "common/dwarf_cu_to_module.h"

 #include <assert.h>

 #if !defined(__ANDROID__)

 #include <cxxabi.h>

 #endif

 #include <inttypes.h>

 #include <algorithm>

 #include <set>

 #include <utility>

 #include <iomanip>

 #include "common/dwarf_line_to_module.h"

 #include "common/logging.h"

 namespace google_breakpad {

 using std::map;

 using std::pair;

 using std::set;

 using std::sort;

 using std::vector;

 // Data provided by a DWARF specification DIE.

 //

 // In DWARF, the DIE for a definition may contain a DW_AT_specification

 // attribute giving the offset of the corresponding declaration DIE, and

 // the definition DIE may omit information given in the declaration. For

 // example, it's common for a function's address range to appear only in

 // its definition DIE, but its name to appear only in its declaration

 // DIE.

 //

 // The dumper needs to be able to follow DW_AT_specification links to

 // bring all this information together in a FUNC record. Conveniently,

 // DIEs that are the target of such links have a DW_AT_declaration flag

 // set, so we can identify them when we first see them, and record their

 // contents for later reference.

 //

 // A Specification holds information gathered from a declaration DIE that

 // we may need if we find a DW_AT_specification link pointing to it.

 struct DwarfCUToModule::Specification {

   // The qualified name that can be found by demangling DW_AT_MIPS_linkage_name.

   string qualified_name;

   // The name of the enclosing scope, or the empty string if there is none.

   string enclosing_name;

   // The name for the specification DIE itself, without any enclosing

   // name components.

   string unqualified_name;

 };

 // An abstract origin -- base definition of an inline function.

 struct AbstractOrigin {

   AbstractOrigin() : name() {}

   AbstractOrigin(const string& name) : name(name) {}

   string name;

 };

 typedef map<uint64, AbstractOrigin> AbstractOriginByOffset;

 // Data global to the DWARF-bearing file that is private to the

 // DWARF-to-Module process.

 struct DwarfCUToModule::FilePrivate {

   // A set of strings used in this CU. Before storing a string in one of

   // our data structures, insert it into this set, and then use the string

   // from the set.

   //

   // In some STL implementations, strings are reference-counted internally,

   // meaning that simply using strings from this set, even if passed by

   // value, assigned, or held directly in structures and containers

   // (map<string, ...>, for example), causes those strings to share a

   // single instance of each distinct piece of text. GNU's libstdc++ uses

   // reference counts, and I believe MSVC did as well, at some point.

   // However, C++ '11 implementations are moving away from reference

   // counting.

   //

   // In other implementations, string assignments copy the string's text,

   // so this set will actually hold yet another copy of the string (although

   // everything will still work). To improve memory consumption portably,

   // we will probably need to use pointers to strings held in this set.

   set<string> common_strings;

   // A map from offsets of DIEs within the .debug_info section to

   // Specifications describing those DIEs. Specification references can

   // cross compilation unit boundaries.

   SpecificationByOffset specifications;

   AbstractOriginByOffset origins;

 };

 DwarfCUToModule::FileContext::FileContext(const string &filename_arg,

                                           Module *module_arg)

     : filename(filename_arg), module(module_arg) {

   file_private = new FilePrivate();

 }

 DwarfCUToModule::FileContext::~FileContext() {

   delete file_private;

 }

 // Information global to the particular compilation unit we're

 // parsing. This is for data shared across the CU's entire DIE tree,

 // and parameters from the code invoking the CU parser.

 struct DwarfCUToModule::CUContext {

   CUContext(FileContext *file_context_arg, WarningReporter *reporter_arg)

       : file_context(file_context_arg),

         reporter(reporter_arg),

         language(Language::CPlusPlus) { }

   ~CUContext() {

     for (vector<Module::Function *>::iterator it = functions.begin();

          it != functions.end(); it++)

       delete *it;

   };

   // The DWARF-bearing file into which this CU was incorporated.

   FileContext *file_context;

   // For printing error messages.

   WarningReporter *reporter;

   // The source language of this compilation unit.

   const Language *language;

   // The functions defined in this compilation unit. We accumulate

   // them here during parsing. Then, in DwarfCUToModule::Finish, we

   // assign them lines and add them to file_context->module.

   //

   // Destroying this destroys all the functions this vector points to.

   vector<Module::Function *> functions;

 };

 // Information about the context of a particular DIE. This is for

 // information that changes as we descend the tree towards the leaves:

 // the containing classes/namespaces, etc.

 struct DwarfCUToModule::DIEContext {

   // The fully-qualified name of the context. For example, for a

   // tree like:

   //

   // DW_TAG_namespace Foo

   //   DW_TAG_class Bar

   //     DW_TAG_subprogram Baz

   //

   // in a C++ compilation unit, the DIEContext's name for the

   // DW_TAG_subprogram DIE would be "Foo::Bar". The DIEContext's

   // name for the DW_TAG_namespace DIE would be "".

   string name;

 };

 // An abstract base class for all the dumper's DIE handlers.

 class DwarfCUToModule::GenericDIEHandler: public dwarf2reader::DIEHandler {

  public:

   // Create a handler for the DIE at OFFSET whose compilation unit is

   // described by CU_CONTEXT, and whose immediate context is described

   // by PARENT_CONTEXT.

   GenericDIEHandler(CUContext *cu_context, DIEContext *parent_context,

                     uint64 offset)

       : cu_context_(cu_context),

         parent_context_(parent_context),

         offset_(offset),

         declaration_(false),

         specification_(NULL) { }

   // Derived classes' ProcessAttributeUnsigned can defer to this to

   // handle DW_AT_declaration, or simply not override it.

   void ProcessAttributeUnsigned(enum DwarfAttribute attr,

                                 enum DwarfForm form,

                                 uint64 data);

   // Derived classes' ProcessAttributeReference can defer to this to

   // handle DW_AT_specification, or simply not override it.

   void ProcessAttributeReference(enum DwarfAttribute attr,

                                  enum DwarfForm form,

                                  uint64 data);

   // Derived classes' ProcessAttributeReference can defer to this to

   // handle DW_AT_specification, or simply not override it.

   void ProcessAttributeString(enum DwarfAttribute attr,

                               enum DwarfForm form,

                               const string &data);

  protected:

   // Compute and return the fully-qualified name of the DIE. If this

   // DIE is a declaration DIE, to be cited by other DIEs'

   // DW_AT_specification attributes, record its enclosing name and

   // unqualified name in the specification table.

   //

   // Use this from EndAttributes member functions, not ProcessAttribute*

   // functions; only the former can be sure that all the DIE's attributes

   // have been seen.

   string ComputeQualifiedName();

   CUContext *cu_context_;

   DIEContext *parent_context_;

   uint64 offset_;

   // Place the name in the global set of strings. Even though this looks

   // like a copy, all the major std::string implementations use reference

   // counting internally, so the effect is to have all the data structures

   // share copies of strings whenever possible.

   // FIXME: Should this return something like a string_ref to avoid the

   // assumption about how strings are implemented?

   string AddStringToPool(const string &str);

   // If this DIE has a DW_AT_declaration attribute, this is its value.

   // It is false on DIEs with no DW_AT_declaration attribute.

   bool declaration_;

   // If this DIE has a DW_AT_specification attribute, this is the

   // Specification structure for the DIE the attribute refers to.

   // Otherwise, this is NULL.

   Specification *specification_;

   // The value of the DW_AT_name attribute, or the empty string if the

   // DIE has no such attribute.

   string name_attribute_;

   // The demangled value of the DW_AT_MIPS_linkage_name attribute, or the empty

   // string if the DIE has no such attribute or its content could not be

   // demangled.

   string demangled_name_;

 };

 void DwarfCUToModule::GenericDIEHandler::ProcessAttributeUnsigned(

     enum DwarfAttribute attr,

     enum DwarfForm form,

     uint64 data) {

   switch (attr) {

     case dwarf2reader::DW_AT_declaration: declaration_ = (data != 0); break;

     default: break;

   }

 }

 void DwarfCUToModule::GenericDIEHandler::ProcessAttributeReference(

     enum DwarfAttribute attr,

     enum DwarfForm form,

     uint64 data) {

   switch (attr) {

     case dwarf2reader::DW_AT_specification: {

       // Find the Specification to which this attribute refers, and

       // set specification_ appropriately. We could do more processing

       // here, but it's better to leave the real work to our

       // EndAttribute member function, at which point we know we have

       // seen all the DIE's attributes.

       FileContext *file_context = cu_context_->file_context;

       SpecificationByOffset *specifications

           = &file_context->file_private->specifications;

       SpecificationByOffset::iterator spec = specifications->find(data);

       if (spec != specifications->end()) {

         specification_ = &spec->second;

       } else {

         // Technically, there's no reason a DW_AT_specification

         // couldn't be a forward reference, but supporting that would

         // be a lot of work (changing to a two-pass structure), and I

         // don't think any producers we care about ever emit such

         // things.

         cu_context_->reporter->UnknownSpecification(offset_, data);

       }

       break;

     }

     default: break;

   }

 }

 string DwarfCUToModule::GenericDIEHandler::AddStringToPool(const string &str) {

   pair<set<string>::iterator, bool> result =

     cu_context_->file_context->file_private->common_strings.insert(str);

   return *result.first;

 }

 void DwarfCUToModule::GenericDIEHandler::ProcessAttributeString(

     enum DwarfAttribute attr,

     enum DwarfForm form,

     const string &data) {

   switch (attr) {

     case dwarf2reader::DW_AT_name:

       name_attribute_ = AddStringToPool(data);

       break;

     case dwarf2reader::DW_AT_MIPS_linkage_name: {

       char* demangled = NULL;

 #if !defined(__ANDROID__)

       demangled = abi::__cxa_demangle(data.c_str(), NULL, NULL, NULL);

 #endif

       if (demangled) {

         demangled_name_ = AddStringToPool(demangled);

         free(reinterpret_cast<void*>(demangled));

       }

       break;

     }

     default: break;

   }

 }

 string DwarfCUToModule::GenericDIEHandler::ComputeQualifiedName() {

   // Use the demangled name, if one is available. Demangled names are

   // preferable to those inferred from the DWARF structure because they

   // include argument types.

   const string *qualified_name = NULL;

   if (!demangled_name_.empty()) {

     // Found it is this DIE.

     qualified_name = &demangled_name_;

   } else if (specification_ && !specification_->qualified_name.empty()) {

     // Found it on the specification.

     qualified_name = &specification_->qualified_name;

   }

   const string *unqualified_name;

   const string *enclosing_name;

   if (!qualified_name) {

     // Find our unqualified name. If the DIE has its own DW_AT_name

     // attribute, then use that; otherwise, check our specification.

     if (name_attribute_.empty() && specification_)

       unqualified_name = &specification_->unqualified_name;

     else

       unqualified_name = &name_attribute_;

     // Find the name of our enclosing context. If we have a

     // specification, it's the specification's enclosing context that

     // counts; otherwise, use this DIE's context.

     if (specification_)

       enclosing_name = &specification_->enclosing_name;

     else

       enclosing_name = &parent_context_->name;

   }

   // If this DIE was marked as a declaration, record its names in the

   // specification table.

   if (declaration_) {

     FileContext *file_context = cu_context_->file_context;

     Specification spec;

     if (qualified_name)

       spec.qualified_name = *qualified_name;

     else {

       spec.enclosing_name = *enclosing_name;

       spec.unqualified_name = *unqualified_name;

     }

     file_context->file_private->specifications[offset_] = spec;

   }

   if (qualified_name)

     return *qualified_name;

   // Combine the enclosing name and unqualified name to produce our

   // own fully-qualified name.

   return cu_context_->language->MakeQualifiedName(*enclosing_name,

                                                   *unqualified_name);

 }

 // A handler class for DW_TAG_subprogram DIEs.

 class DwarfCUToModule::FuncHandler: public GenericDIEHandler {

  public:

   FuncHandler(CUContext *cu_context, DIEContext *parent_context,

               uint64 offset)

       : GenericDIEHandler(cu_context, parent_context, offset),

         low_pc_(0), high_pc_(0), high_pc_form_(dwarf2reader::DW_FORM_addr),

         abstract_origin_(NULL), inline_(false) { }

   void ProcessAttributeUnsigned(enum DwarfAttribute attr,

                                 enum DwarfForm form,

                                 uint64 data);

   void ProcessAttributeSigned(enum DwarfAttribute attr,

                               enum DwarfForm form,

                               int64 data);

   void ProcessAttributeReference(enum DwarfAttribute attr,

                                  enum DwarfForm form,

                                  uint64 data);

   bool EndAttributes();

   void Finish();

  private:

   // The fully-qualified name, as derived from name_attribute_,

   // specification_, parent_context_.  Computed in EndAttributes.

   string name_;

   uint64 low_pc_, high_pc_; // DW_AT_low_pc, DW_AT_high_pc

   DwarfForm high_pc_form_; // DW_AT_high_pc can be length or address.

   const AbstractOrigin* abstract_origin_;

   bool inline_;

 };

 void DwarfCUToModule::FuncHandler::ProcessAttributeUnsigned(

     enum DwarfAttribute attr,

     enum DwarfForm form,

     uint64 data) {

   switch (attr) {

     // If this attribute is present at all --- even if its value is

     // DW_INL_not_inlined --- then GCC may cite it as someone else's

     // DW_AT_abstract_origin attribute.

     case dwarf2reader::DW_AT_inline:      inline_  = true; break;

     case dwarf2reader::DW_AT_low_pc:      low_pc_  = data; break;

     case dwarf2reader::DW_AT_high_pc:

       high_pc_form_ = form;

       high_pc_ = data;

       break;

     default:

       GenericDIEHandler::ProcessAttributeUnsigned(attr, form, data);

       break;

   }

 }

 void DwarfCUToModule::FuncHandler::ProcessAttributeSigned(

     enum DwarfAttribute attr,

     enum DwarfForm form,

     int64 data) {

   switch (attr) {

     // If this attribute is present at all --- even if its value is

     // DW_INL_not_inlined --- then GCC may cite it as someone else's

     // DW_AT_abstract_origin attribute.

     case dwarf2reader::DW_AT_inline:      inline_  = true; break;

     default:

       break;

   }

 }

 void DwarfCUToModule::FuncHandler::ProcessAttributeReference(

     enum DwarfAttribute attr,

     enum DwarfForm form,

     uint64 data) {

   switch(attr) {

     case dwarf2reader::DW_AT_abstract_origin: {

       const AbstractOriginByOffset& origins =

           cu_context_->file_context->file_private->origins;

       AbstractOriginByOffset::const_iterator origin = origins.find(data);

       if (origin != origins.end()) {

         abstract_origin_ = &(origin->second);

       } else {

         cu_context_->reporter->UnknownAbstractOrigin(offset_, data);

       }

       break;

     }

     default:

       GenericDIEHandler::ProcessAttributeReference(attr, form, data);

       break;

   }

 }

 bool DwarfCUToModule::FuncHandler::EndAttributes() {

   // Compute our name, and record a specification, if appropriate.

   name_ = ComputeQualifiedName();

   if (name_.empty() && abstract_origin_) {

     name_ = abstract_origin_->name;

   }

   return true;

 }

 void DwarfCUToModule::FuncHandler::Finish() {

   // Make high_pc_ an address, if it isn't already.

   if (high_pc_form_ != dwarf2reader::DW_FORM_addr) {

     high_pc_ += low_pc_;

   }

   // Did we collect the information we need?  Not all DWARF function

   // entries have low and high addresses (for example, inlined

   // functions that were never used), but all the ones we're

   // interested in cover a non-empty range of bytes.

   if (low_pc_ < high_pc_) {

     // Create a Module::Function based on the data we've gathered, and

     // add it to the functions_ list.

     Module::Function *func = new Module::Function;

     // Malformed DWARF may omit the name, but all Module::Functions must

     // have names.

     if (!name_.empty()) {

       func->name = name_;

     } else {

       cu_context_->reporter->UnnamedFunction(offset_);

       func->name = "<name omitted>";

     }

     func->address = low_pc_;

     func->size = high_pc_ - low_pc_;

     func->parameter_size = 0;

     if (func->address) {

        // If the function address is zero this is a sign that this function

        // description is just empty debug data and should just be discarded.

        cu_context_->functions.push_back(func);

      }

   } else if (inline_) {

     AbstractOrigin origin(name_);

     cu_context_->file_context->file_private->origins[offset_] = origin;

   }

 }

 // A handler for DIEs that contain functions and contribute a

 // component to their names: namespaces, classes, etc.

 class DwarfCUToModule::NamedScopeHandler: public GenericDIEHandler {

  public:

   NamedScopeHandler(CUContext *cu_context, DIEContext *parent_context,

                     uint64 offset)

       : GenericDIEHandler(cu_context, parent_context, offset) { }

   bool EndAttributes();

   DIEHandler *FindChildHandler(uint64 offset, enum DwarfTag tag);

  private:

   DIEContext child_context_; // A context for our children.

 };

 bool DwarfCUToModule::NamedScopeHandler::EndAttributes() {

   child_context_.name = ComputeQualifiedName();

   return true;

 }

 dwarf2reader::DIEHandler *DwarfCUToModule::NamedScopeHandler::FindChildHandler(

     uint64 offset,

     enum DwarfTag tag) {

   switch (tag) {

     case dwarf2reader::DW_TAG_subprogram:

       return new FuncHandler(cu_context_, &child_context_, offset);

     case dwarf2reader::DW_TAG_namespace:

     case dwarf2reader::DW_TAG_class_type:

     case dwarf2reader::DW_TAG_structure_type:

     case dwarf2reader::DW_TAG_union_type:

       return new NamedScopeHandler(cu_context_, &child_context_, offset);

     default:

       return NULL;

   }

 }

 void DwarfCUToModule::WarningReporter::CUHeading() {

   if (printed_cu_header_)

     return;

   BPLOG(INFO)

     << filename_ << ": in compilation unit '" << cu_name_

     << "' (offset 0x" << std::setbase(16) << cu_offset_ << std::setbase(10)

     << "):";

   printed_cu_header_ = true;

 }

 void DwarfCUToModule::WarningReporter::UnknownSpecification(uint64 offset,

                                                             uint64 target) {

   CUHeading();

   BPLOG(INFO)

     << filename_ << ": the DIE at offset 0x" 

     << std::setbase(16) << offset << std::setbase(10)

     << " has a DW_AT_specification attribute referring to the die at offset 0x"

     << std::setbase(16) << target << std::setbase(10)

     << ", which either was not marked as a declaration, or comes "

     << "later in the file";

 }

 void DwarfCUToModule::WarningReporter::UnknownAbstractOrigin(uint64 offset,

                                                              uint64 target) {

   CUHeading();

   BPLOG(INFO)

     << filename_ << ": the DIE at offset 0x" 

     << std::setbase(16) << offset << std::setbase(10)

     << " has a DW_AT_abstract_origin attribute referring to the die at"

     << " offset 0x" << std::setbase(16) << target << std::setbase(10)

     << ", which either was not marked as an inline, or comes "

     << "later in the file";

 }

 void DwarfCUToModule::WarningReporter::MissingSection(const string &name) {

   CUHeading();

   BPLOG(INFO) << filename_ << ": warning: couldn't find DWARF '"

     << name << "' section";

 }

 void DwarfCUToModule::WarningReporter::BadLineInfoOffset(uint64 offset) {

   CUHeading();

   BPLOG(INFO) << filename_ << ": warning: line number data offset beyond "

     << "end of '.debug_line' section";

 }

 void DwarfCUToModule::WarningReporter::UncoveredHeading() {

   if (printed_unpaired_header_)

     return;

   CUHeading();

   BPLOG(INFO) << filename_ << ": warning: skipping unpaired lines/functions:";

   printed_unpaired_header_ = true;

 }

 void DwarfCUToModule::WarningReporter::UncoveredFunction(

     const Module::Function &function) {

   if (!uncovered_warnings_enabled_)

     return;

   UncoveredHeading();

   BPLOG(INFO) << "    function" << (function.size == 0 ? " (zero-length)" : "")

     << ": " << function.name;

 }

 void DwarfCUToModule::WarningReporter::UncoveredLine(const Module::Line &line) {

   if (!uncovered_warnings_enabled_)

     return;

   UncoveredHeading();

   BPLOG(INFO) << "    line" << (line.size == 0 ? " (zero-length)" : "")

     << ": " << line.file->name << ":" << line.number

     << " at 0x" << std::setbase(16) << line.address << std::setbase(10);

 }

 void DwarfCUToModule::WarningReporter::UnnamedFunction(uint64 offset) {

   CUHeading();

   BPLOG(INFO) << filename_ << ": warning: function at offset 0x"

     << std::setbase(16) << offset << std::setbase(10) << " has no name";

 }

 DwarfCUToModule::DwarfCUToModule(FileContext *file_context,

                                  LineToModuleHandler *line_reader,

                                  WarningReporter *reporter)

     : line_reader_(line_reader), has_source_line_info_(false) { 

   cu_context_ = new CUContext(file_context, reporter);

   child_context_ = new DIEContext();

 }

 DwarfCUToModule::~DwarfCUToModule() {

   delete cu_context_;

   delete child_context_;

 }

 void DwarfCUToModule::ProcessAttributeSigned(enum DwarfAttribute attr,

                                              enum DwarfForm form,

                                              int64 data) {

   switch (attr) {

     case dwarf2reader::DW_AT_language: // source language of this CU

       SetLanguage(static_cast<DwarfLanguage>(data));

       break;

     default:

       break;

   }

 }

 void DwarfCUToModule::ProcessAttributeUnsigned(enum DwarfAttribute attr,

                                                enum DwarfForm form,

                                                uint64 data) {

   switch (attr) {

     case dwarf2reader::DW_AT_stmt_list: // Line number information.

       has_source_line_info_ = true;

       source_line_offset_ = data;

       break;

     case dwarf2reader::DW_AT_language: // source language of this CU

       SetLanguage(static_cast<DwarfLanguage>(data));

       break;

     default:

       break;

   }

 }

 void DwarfCUToModule::ProcessAttributeString(enum DwarfAttribute attr,

                                              enum DwarfForm form,

                                              const string &data) {

   switch (attr) {

     case dwarf2reader::DW_AT_name:

       cu_context_->reporter->SetCUName(data);

       break;

     case dwarf2reader::DW_AT_comp_dir:

       line_reader_->StartCompilationUnit(data);

       break;

     default:

       break;

   }

 }

 bool DwarfCUToModule::EndAttributes() {

   return true;

 }

 dwarf2reader::DIEHandler *DwarfCUToModule::FindChildHandler(

     uint64 offset,

     enum DwarfTag tag) {

   switch (tag) {

     case dwarf2reader::DW_TAG_subprogram:

       return new FuncHandler(cu_context_, child_context_, offset);

     case dwarf2reader::DW_TAG_namespace:

     case dwarf2reader::DW_TAG_class_type:

     case dwarf2reader::DW_TAG_structure_type:

     case dwarf2reader::DW_TAG_union_type:

       return new NamedScopeHandler(cu_context_, child_context_, offset);

     default:

       return NULL;

   }

 }

 void DwarfCUToModule::SetLanguage(DwarfLanguage language) {

   switch (language) {

     case dwarf2reader::DW_LANG_Java:

       cu_context_->language = Language::Java;

       break;

     // DWARF has no generic language code for assembly language; this is

     // what the GNU toolchain uses.

     case dwarf2reader::DW_LANG_Mips_Assembler:

       cu_context_->language = Language::Assembler;

       break;

     // C++ covers so many cases that it probably has some way to cope

     // with whatever the other languages throw at us. So make it the

     // default.

     //

     // Objective C and Objective C++ seem to create entries for

     // methods whose DW_AT_name values are already fully-qualified:

     // "-[Classname method:]".  These appear at the top level.

     // 

     // DWARF data for C should never include namespaces or functions

     // nested in struct types, but if it ever does, then C++'s

     // notation is probably not a bad choice for that.

     default:

     case dwarf2reader::DW_LANG_ObjC:

     case dwarf2reader::DW_LANG_ObjC_plus_plus:

     case dwarf2reader::DW_LANG_C:

     case dwarf2reader::DW_LANG_C89:

     case dwarf2reader::DW_LANG_C99:

     case dwarf2reader::DW_LANG_C_plus_plus:

       cu_context_->language = Language::CPlusPlus;

       break;

   }

 }

 void DwarfCUToModule::ReadSourceLines(uint64 offset) {

   const dwarf2reader::SectionMap &section_map

       = cu_context_->file_context->section_map;

   dwarf2reader::SectionMap::const_iterator map_entry

       = section_map.find(".debug_line");

   // Mac OS X puts DWARF data in sections whose names begin with "__"

   // instead of ".".

   if (map_entry == section_map.end())

     map_entry = section_map.find("__debug_line");

   if (map_entry == section_map.end()) {

     cu_context_->reporter->MissingSection(".debug_line");

     return;

   }

   const char *section_start = map_entry->second.first;

   uint64 section_length = map_entry->second.second;

   if (offset >= section_length) {

     cu_context_->reporter->BadLineInfoOffset(offset);

     return;

   }

   line_reader_->ReadProgram(section_start + offset, section_length - offset,

                             cu_context_->file_context->module, &lines_);

 }

 namespace {

 // Return true if ADDRESS falls within the range of ITEM.

 template <class T>

 inline bool within(const T &item, Module::Address address) {

   // Because Module::Address is unsigned, and unsigned arithmetic

   // wraps around, this will be false if ADDRESS falls before the

   // start of ITEM, or if it falls after ITEM's end.

   return address - item.address < item.size;

 }

 }

 void DwarfCUToModule::AssignLinesToFunctions() {

   vector<Module::Function *> *functions = &cu_context_->functions;

   WarningReporter *reporter = cu_context_->reporter;

   // This would be simpler if we assumed that source line entries

   // don't cross function boundaries.  However, there's no real reason

   // to assume that (say) a series of function definitions on the same

   // line wouldn't get coalesced into one line number entry.  The

   // DWARF spec certainly makes no such promises.

   //

   // So treat the functions and lines as peers, and take the trouble

   // to compute their ranges' intersections precisely.  In any case,

   // the hair here is a constant factor for performance; the

   // complexity from here on out is linear.

   // Put both our functions and lines in order by address.

   std::sort(functions->begin(), functions->end(),

             Module::Function::CompareByAddress);

   std::sort(lines_.begin(), lines_.end(), Module::Line::CompareByAddress);

   // The last line that we used any piece of.  We use this only for

   // generating warnings.

   const Module::Line *last_line_used = NULL;

   // The last function and line we warned about --- so we can avoid

   // doing so more than once.

   const Module::Function *last_function_cited = NULL;

   const Module::Line *last_line_cited = NULL;

   // Make a single pass through both vectors from lower to higher

   // addresses, populating each Function's lines vector with lines

   // from our lines_ vector that fall within the function's address

   // range.

   vector<Module::Function *>::iterator func_it = functions->begin();

   vector<Module::Line>::const_iterator line_it = lines_.begin();

   Module::Address current;

   // Pointers to the referents of func_it and line_it, or NULL if the

   // iterator is at the end of the sequence.

   Module::Function *func;

   const Module::Line *line;

   // Start current at the beginning of the first line or function,

   // whichever is earlier.

   if (func_it != functions->end() && line_it != lines_.end()) {

     func = *func_it;

     line = &*line_it;

     current = std::min(func->address, line->address);

   } else if (line_it != lines_.end()) {

     func = NULL;

     line = &*line_it;

     current = line->address;

   } else if (func_it != functions->end()) {

     func = *func_it;

     line = NULL;

     current = (*func_it)->address;

   } else {

     return;

   }

   while (func || line) {

     // This loop has two invariants that hold at the top.

     //

     // First, at least one of the iterators is not at the end of its

     // sequence, and those that are not refer to the earliest

     // function or line that contains or starts after CURRENT.

     //

     // Note that every byte is in one of four states: it is covered

     // or not covered by a function, and, independently, it is

     // covered or not covered by a line.

     //

     // The second invariant is that CURRENT refers to a byte whose

     // state is different from its predecessor, or it refers to the

     // first byte in the address space. In other words, CURRENT is

     // always the address of a transition.

     //

     // Note that, although each iteration advances CURRENT from one

     // transition address to the next in each iteration, it might

     // not advance the iterators. Suppose we have a function that

     // starts with a line, has a gap, and then a second line, and

     // suppose that we enter an iteration with CURRENT at the end of

     // the first line. The next transition address is the start of

     // the second line, after the gap, so the iteration should

     // advance CURRENT to that point. At the head of that iteration,

     // the invariants require that the line iterator be pointing at

     // the second line. But this is also true at the head of the

     // next. And clearly, the iteration must not change the function

     // iterator. So neither iterator moves.

     // Assert the first invariant (see above).

     assert(!func || current < func->address || within(*func, current));

     assert(!line || current < line->address || within(*line, current));

     // The next transition after CURRENT.

     Module::Address next_transition;

     // Figure out which state we're in, add lines or warn, and compute

     // the next transition address.

     if (func && current >= func->address) {

       if (line && current >= line->address) {

         // Covered by both a line and a function.

         Module::Address func_left = func->size - (current - func->address);

         Module::Address line_left = line->size - (current - line->address);

         // This may overflow, but things work out.

         next_transition = current + std::min(func_left, line_left);

         Module::Line l = *line;

         l.address = current;

         l.size = next_transition - current;

         func->lines.push_back(l);

         last_line_used = line;

       } else {

         // Covered by a function, but no line.

         if (func != last_function_cited) {

           reporter->UncoveredFunction(*func);

           last_function_cited = func;

         }

         if (line && within(*func, line->address))

           next_transition = line->address;

         else

           // If this overflows, we'll catch it below.

           next_transition = func->address + func->size;

       }

     } else {

       if (line && current >= line->address) {

         // Covered by a line, but no function.

         //

         // If GCC emits padding after one function to align the start

         // of the next, then it will attribute the padding

         // instructions to the last source line of function (to reduce

         // the size of the line number info), but omit it from the

         // DW_AT_{low,high}_pc range given in .debug_info (since it

         // costs nothing to be precise there). If we did use at least

         // some of the line we're about to skip, and it ends at the

         // start of the next function, then assume this is what

         // happened, and don't warn.

         if (line != last_line_cited

             && !(func

                  && line == last_line_used

                  && func->address - line->address == line->size)) {

           reporter->UncoveredLine(*line);

           last_line_cited = line;

         }

         if (func && within(*line, func->address))

           next_transition = func->address;

         else

           // If this overflows, we'll catch it below.

           next_transition = line->address + line->size;

       } else {

         // Covered by neither a function nor a line. By the invariant,

         // both func and line begin after CURRENT. The next transition

         // is the start of the next function or next line, whichever

         // is earliest.

         assert (func || line);

         if (func && line)

           next_transition = std::min(func->address, line->address);

         else if (func)

           next_transition = func->address;

         else

           next_transition = line->address;

       }

     }

     // If a function or line abuts the end of the address space, then

     // next_transition may end up being zero, in which case we've completed

     // our pass. Handle that here, instead of trying to deal with it in

     // each place we compute next_transition.

     if (!next_transition)

       break;

     // Advance iterators as needed. If lines overlap or functions overlap,

     // then we could go around more than once. We don't worry too much

     // about what result we produce in that case, just as long as we don't

     // hang or crash.

     while (func_it != functions->end()

            && next_transition >= (*func_it)->address

            && !within(**func_it, next_transition))

       func_it++;

     func = (func_it != functions->end()) ? *func_it : NULL;

     while (line_it != lines_.end()

            && next_transition >= line_it->address

            && !within(*line_it, next_transition))

       line_it++;

     line = (line_it != lines_.end()) ? &*line_it : NULL;

     // We must make progress.

     assert(next_transition > current);

     current = next_transition;

   }

 }

 void DwarfCUToModule::Finish() {

   // Assembly language files have no function data, and that gives us

   // no place to store our line numbers (even though the GNU toolchain

   // will happily produce source line info for assembly language

   // files).  To avoid spurious warnings about lines we can't assign

   // to functions, skip CUs in languages that lack functions.

   if (!cu_context_->language->HasFunctions())

     return;

   // Read source line info, if we have any.

   if (has_source_line_info_)

     ReadSourceLines(source_line_offset_);

   vector<Module::Function *> *functions = &cu_context_->functions;

   // Dole out lines to the appropriate functions.

   AssignLinesToFunctions();

   // Add our functions, which now have source lines assigned to them,

   // to module_.

   cu_context_->file_context->module->AddFunctions(functions->begin(),

                                                   functions->end());

   // Ownership of the function objects has shifted from cu_context to

   // the Module.

   functions->clear();

 }

 bool DwarfCUToModule::StartCompilationUnit(uint64 offset,

                                            uint8 address_size,

                                            uint8 offset_size,

                                            uint64 cu_length,

                                            uint8 dwarf_version) {

   return dwarf_version >= 2;

 }

 bool DwarfCUToModule::StartRootDIE(uint64 offset, enum DwarfTag tag) {

   // We don't deal with partial compilation units (the only other tag

   // likely to be used for root DIE).

   return tag == dwarf2reader::DW_TAG_compile_unit;

 }

 } // namespace google_breakpad