First round of dead file removal

obsolete/breakpad/common/dwarf/dwarf2reader.h

-// -*- mode: C++ -*-
-
-// 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.
-
-// CFI reader author: Jim Blandy <jimb@mozilla.com> <jimb@red-bean.com>
-
-// This file contains definitions related to the DWARF2/3 reader and
-// it's handler interfaces.
-// The DWARF2/3 specification can be found at
-// http://dwarf.freestandards.org and should be considered required
-// reading if you wish to modify the implementation.
-// Only a cursory attempt is made to explain terminology that is
-// used here, as it is much better explained in the standard documents
-#ifndef COMMON_DWARF_DWARF2READER_H__
-#define COMMON_DWARF_DWARF2READER_H__
-
-#include <list>
-#include <map>
-#include <string>
-#include <utility>
-#include <vector>
-
-#ifdef WIN32
-#undef min
-#undef max
-#pragma warning(disable:4800 4244)
-#endif
-
-#include "common/dwarf/bytereader.h"
-#include "common/dwarf/dwarf2enums.h"
-#include "common/dwarf/types.h"
-
-using namespace std;
-
-namespace dwarf2reader {
-struct LineStateMachine;
-class Dwarf2Handler;
-class LineInfoHandler;
-
-// This maps from a string naming a section to a pair containing a
-// the data for the section, and the size of the section.
-typedef map<string, pair<const char*, uint64> > SectionMap;
-typedef list<pair<enum DwarfAttribute, enum DwarfForm> > AttributeList;
-typedef AttributeList::iterator AttributeIterator;
-typedef AttributeList::const_iterator ConstAttributeIterator;
-
-struct LineInfoHeader {
-  uint64 total_length;
-  uint16 version;
-  uint64 prologue_length;
-  uint8 min_insn_length; // insn stands for instructin
-  bool default_is_stmt; // stmt stands for statement
-  int8 line_base;
-  uint8 line_range;
-  uint8 opcode_base;
-  // Use a pointer so that signalsafe_addr2line is able to use this structure
-  // without heap allocation problem.
-  vector<unsigned char> *std_opcode_lengths;
-};
-
-class LineInfo {
- public:
-
-  // Initializes a .debug_line reader. Buffer and buffer length point
-  // to the beginning and length of the line information to read.
-  // Reader is a ByteReader class that has the endianness set
-  // properly.
-  LineInfo(const char* buffer_, uint64 buffer_length,
-           ByteReader* reader, LineInfoHandler* handler);
-
-  virtual ~LineInfo() {
-    if (header_.std_opcode_lengths) {
-      delete header_.std_opcode_lengths;
-    }
-  }
-
-  // Start processing line info, and calling callbacks in the handler.
-  // Consumes the line number information for a single compilation unit.
-  // Returns the number of bytes processed.
-  uint64 Start();
-
-  // Process a single line info opcode at START using the state
-  // machine at LSM.  Return true if we should define a line using the
-  // current state of the line state machine.  Place the length of the
-  // opcode in LEN.
-  // If LSM_PASSES_PC is non-NULL, this function also checks if the lsm
-  // passes the address of PC. In other words, LSM_PASSES_PC will be
-  // set to true, if the following condition is met.
-  //
-  // lsm's old address < PC <= lsm's new address
-  static bool ProcessOneOpcode(ByteReader* reader,
-                               LineInfoHandler* handler,
-                               const struct LineInfoHeader &header,
-                               const char* start,
-                               struct LineStateMachine* lsm,
-                               size_t* len,
-                               uintptr pc,
-                               bool *lsm_passes_pc);
-
- private:
-  // Reads the DWARF2/3 header for this line info.
-  void ReadHeader();
-
-  // Reads the DWARF2/3 line information
-  void ReadLines();
-
-  // The associated handler to call processing functions in
-  LineInfoHandler* handler_;
-
-  // The associated ByteReader that handles endianness issues for us
-  ByteReader* reader_;
-
-  // A DWARF2/3 line info header.  This is not the same size as
-  // in the actual file, as the one in the file may have a 32 bit or
-  // 64 bit lengths
-
-  struct LineInfoHeader header_;
-
-  // buffer is the buffer for our line info, starting at exactly where
-  // the line info to read is.  after_header is the place right after
-  // the end of the line information header.
-  const char* buffer_;
-  uint64 buffer_length_;
-  const char* after_header_;
-};
-
-// This class is the main interface between the line info reader and
-// the client.  The virtual functions inside this get called for
-// interesting events that happen during line info reading.  The
-// default implementation does nothing
-
-class LineInfoHandler {
- public:
-  LineInfoHandler() { }
-
-  virtual ~LineInfoHandler() { }
-
-  // Called when we define a directory.  NAME is the directory name,
-  // DIR_NUM is the directory number
-  virtual void DefineDir(const string& name, uint32 dir_num) { }
-
-  // Called when we define a filename. NAME is the filename, FILE_NUM
-  // is the file number which is -1 if the file index is the next
-  // index after the last numbered index (this happens when files are
-  // dynamically defined by the line program), DIR_NUM is the
-  // directory index for the directory name of this file, MOD_TIME is
-  // the modification time of the file, and LENGTH is the length of
-  // the file
-  virtual void DefineFile(const string& name, int32 file_num,
-                          uint32 dir_num, uint64 mod_time,
-                          uint64 length) { }
-
-  // Called when the line info reader has a new line, address pair
-  // ready for us. ADDRESS is the address of the code, LENGTH is the
-  // length of its machine code in bytes, FILE_NUM is the file number
-  // containing the code, LINE_NUM is the line number in that file for
-  // the code, and COLUMN_NUM is the column number the code starts at,
-  // if we know it (0 otherwise).
-  virtual void AddLine(uint64 address, uint64 length,
-                       uint32 file_num, uint32 line_num, uint32 column_num) { }
-};
-
-// The base of DWARF2/3 debug info is a DIE (Debugging Information
-// Entry.
-// DWARF groups DIE's into a tree and calls the root of this tree a
-// "compilation unit".  Most of the time, there is one compilation
-// unit in the .debug_info section for each file that had debug info
-// generated.
-// Each DIE consists of
-
-// 1. a tag specifying a thing that is being described (ie
-// DW_TAG_subprogram for functions, DW_TAG_variable for variables, etc
-// 2. attributes (such as DW_AT_location for location in memory,
-// DW_AT_name for name), and data for each attribute.
-// 3. A flag saying whether the DIE has children or not
-
-// In order to gain some amount of compression, the format of
-// each DIE (tag name, attributes and data forms for the attributes)
-// are stored in a separate table called the "abbreviation table".
-// This is done because a large number of DIEs have the exact same tag
-// and list of attributes, but different data for those attributes.
-// As a result, the .debug_info section is just a stream of data, and
-// requires reading of the .debug_abbrev section to say what the data
-// means.
-
-// As a warning to the user, it should be noted that the reason for
-// using absolute offsets from the beginning of .debug_info is that
-// DWARF2/3 supports referencing DIE's from other DIE's by their offset
-// from either the current compilation unit start, *or* the beginning
-// of the .debug_info section.  This means it is possible to reference
-// a DIE in one compilation unit from a DIE in another compilation
-// unit.  This style of reference is usually used to eliminate
-// duplicated information that occurs across compilation
-// units, such as base types, etc.  GCC 3.4+ support this with
-// -feliminate-dwarf2-dups.  Other toolchains will sometimes do
-// duplicate elimination in the linker.
-
-class CompilationUnit {
- public:
-
-  // Initialize a compilation unit.  This requires a map of sections,
-  // the offset of this compilation unit in the .debug_info section, a
-  // ByteReader, and a Dwarf2Handler class to call callbacks in.
-  CompilationUnit(const SectionMap& sections, uint64 offset,
-                  ByteReader* reader, Dwarf2Handler* handler);
-  virtual ~CompilationUnit() {
-    if (abbrevs_) delete abbrevs_;
-  }
-
-  // Begin reading a Dwarf2 compilation unit, and calling the
-  // callbacks in the Dwarf2Handler
-
-  // Return the full length of the compilation unit, including
-  // headers. This plus the starting offset passed to the constructor
-  // is the offset of the end of the compilation unit --- and the
-  // start of the next compilation unit, if there is one.
-  uint64 Start();
-
- private:
-
-  // This struct represents a single DWARF2/3 abbreviation
-  // The abbreviation tells how to read a DWARF2/3 DIE, and consist of a
-  // tag and a list of attributes, as well as the data form of each attribute.
-  struct Abbrev {
-    uint32 number;
-    enum DwarfTag tag;
-    bool has_children;
-    AttributeList attributes;
-  };
-
-  // A DWARF2/3 compilation unit header.  This is not the same size as
-  // in the actual file, as the one in the file may have a 32 bit or
-  // 64 bit length.
-  struct CompilationUnitHeader {
-    uint64 length;
-    uint16 version;
-    uint64 abbrev_offset;
-    uint8 address_size;
-  } header_;
-
-  // Reads the DWARF2/3 header for this compilation unit.
-  void ReadHeader();
-
-  // Reads the DWARF2/3 abbreviations for this compilation unit
-  void ReadAbbrevs();
-
-  // Processes a single DIE for this compilation unit and return a new
-  // pointer just past the end of it
-  const char* ProcessDIE(uint64 dieoffset,
-                                  const char* start,
-                                  const Abbrev& abbrev);
-
-  // Processes a single attribute and return a new pointer just past the
-  // end of it
-  const char* ProcessAttribute(uint64 dieoffset,
-                                        const char* start,
-                                        enum DwarfAttribute attr,
-                                        enum DwarfForm form);
-
-  // Processes all DIEs for this compilation unit
-  void ProcessDIEs();
-
-  // Skips the die with attributes specified in ABBREV starting at
-  // START, and return the new place to position the stream to.
-  const char* SkipDIE(const char* start,
-                               const Abbrev& abbrev);
-
-  // Skips the attribute starting at START, with FORM, and return the
-  // new place to position the stream to.
-  const char* SkipAttribute(const char* start,
-                                     enum DwarfForm form);
-
-  // Offset from section start is the offset of this compilation unit
-  // from the beginning of the .debug_info section.
-  uint64 offset_from_section_start_;
-
-  // buffer is the buffer for our CU, starting at .debug_info + offset
-  // passed in from constructor.
-  // after_header points to right after the compilation unit header.
-  const char* buffer_;
-  uint64 buffer_length_;
-  const char* after_header_;
-
-  // The associated ByteReader that handles endianness issues for us
-  ByteReader* reader_;
-
-  // The map of sections in our file to buffers containing their data
-  const SectionMap& sections_;
-
-  // The associated handler to call processing functions in
-  Dwarf2Handler* handler_;
-
-  // Set of DWARF2/3 abbreviations for this compilation unit.  Indexed
-  // by abbreviation number, which means that abbrevs_[0] is not
-  // valid.
-  vector<Abbrev>* abbrevs_;
-
-  // String section buffer and length, if we have a string section.
-  // This is here to avoid doing a section lookup for strings in
-  // ProcessAttribute, which is in the hot path for DWARF2 reading.
-  const char* string_buffer_;
-  uint64 string_buffer_length_;
-};
-
-// This class is the main interface between the reader and the
-// client.  The virtual functions inside this get called for
-// interesting events that happen during DWARF2 reading.
-// The default implementation skips everything.
-
-class Dwarf2Handler {
- public:
-  Dwarf2Handler() { }
-
-  virtual ~Dwarf2Handler() { }
-
-  // Start to process a compilation unit at OFFSET from the beginning of the
-  // .debug_info section. Return false if you would like to skip this
-  // compilation unit.
-  virtual bool StartCompilationUnit(uint64 offset, uint8 address_size,
-                                    uint8 offset_size, uint64 cu_length,
-                                    uint8 dwarf_version) { return false; }
-
-  // Start to process a DIE at OFFSET from the beginning of the .debug_info
-  // section. Return false if you would like to skip this DIE.
-  virtual bool StartDIE(uint64 offset, enum DwarfTag tag,
-                        const AttributeList& attrs) { return false; }
-
-  // Called when we have an attribute with unsigned data to give to our
-  // handler. The attribute is for the DIE at OFFSET from the beginning of the
-  // .debug_info section. Its name is ATTR, its form is FORM, and its value is
-  // DATA.
-  virtual void ProcessAttributeUnsigned(uint64 offset,
-                                        enum DwarfAttribute attr,
-                                        enum DwarfForm form,
-                                        uint64 data) { }
-
-  // Called when we have an attribute with signed data to give to our handler.
-  // The attribute is for the DIE at OFFSET from the beginning of the
-  // .debug_info section. Its name is ATTR, its form is FORM, and its value is
-  // DATA.
-  virtual void ProcessAttributeSigned(uint64 offset,
-                                      enum DwarfAttribute attr,
-                                      enum DwarfForm form,
-                                      int64 data) { }
-
-  // Called when we have an attribute whose value is a reference to
-  // another DIE. The attribute belongs to the DIE at OFFSET from the
-  // beginning of the .debug_info section. Its name is ATTR, its form
-  // is FORM, and the offset of the DIE being referred to from the
-  // beginning of the .debug_info section is DATA.
-  virtual void ProcessAttributeReference(uint64 offset,
-                                         enum DwarfAttribute attr,
-                                         enum DwarfForm form,
-                                         uint64 data) { }
-
-  // Called when we have an attribute with a buffer of data to give to our
-  // handler. The attribute is for the DIE at OFFSET from the beginning of the
-  // .debug_info section. Its name is ATTR, its form is FORM, DATA points to
-  // the buffer's contents, and its length in bytes is LENGTH. The buffer is
-  // owned by the caller, not the callee, and may not persist for very long.
-  // If you want the data to be available later, it needs to be copied.
-  virtual void ProcessAttributeBuffer(uint64 offset,
-                                      enum DwarfAttribute attr,
-                                      enum DwarfForm form,
-                                      const char* data,
-                                      uint64 len) { }
-
-  // Called when we have an attribute with string data to give to our handler.
-  // The attribute is for the DIE at OFFSET from the beginning of the
-  // .debug_info section. Its name is ATTR, its form is FORM, and its value is
-  // DATA.
-  virtual void ProcessAttributeString(uint64 offset,
-                                      enum DwarfAttribute attr,
-                                      enum DwarfForm form,
-                                      const string& data) { }
-
-  // Called when finished processing the DIE at OFFSET.
-  // Because DWARF2/3 specifies a tree of DIEs, you may get starts
-  // before ends of the previous DIE, as we process children before
-  // ending the parent.
-  virtual void EndDIE(uint64 offset) { }
-
-};
-
-// This class is a reader for DWARF's Call Frame Information.  CFI
-// describes how to unwind stack frames --- even for functions that do
-// not follow fixed conventions for saving registers, whose frame size
-// varies as they execute, etc.
-//
-// CFI describes, at each machine instruction, how to compute the
-// stack frame's base address, how to find the return address, and
-// where to find the saved values of the caller's registers (if the
-// callee has stashed them somewhere to free up the registers for its
-// own use).
-//
-// For example, suppose we have a function whose machine code looks
-// like this (imagine an assembly language that looks like C, for a
-// machine with 32-bit registers, and a stack that grows towards lower
-// addresses):
-//
-// func:                                ; entry point; return address at sp
-// func+0:      sp = sp - 16            ; allocate space for stack frame
-// func+1:      sp[12] = r0             ; save r0 at sp+12
-// ...                                  ; other code, not frame-related
-// func+10:     sp -= 4; *sp = x        ; push some x on the stack
-// ...                                  ; other code, not frame-related
-// func+20:     r0 = sp[16]             ; restore saved r0
-// func+21:     sp += 20                ; pop whole stack frame
-// func+22:     pc = *sp; sp += 4       ; pop return address and jump to it
-//
-// DWARF CFI is (a very compressed representation of) a table with a
-// row for each machine instruction address and a column for each
-// register showing how to restore it, if possible.
-//
-// A special column named "CFA", for "Canonical Frame Address", tells how
-// to compute the base address of the frame; registers' entries may
-// refer to the CFA in describing where the registers are saved.
-//
-// Another special column, named "RA", represents the return address.
-//
-// For example, here is a complete (uncompressed) table describing the
-// function above:
-// 
-//     insn      cfa    r0      r1 ...  ra
-//     =======================================
-//     func+0:   sp                     cfa[0]
-//     func+1:   sp+16                  cfa[0] 
-//     func+2:   sp+16  cfa[-4]         cfa[0]
-//     func+11:  sp+20  cfa[-4]         cfa[0]
-//     func+21:  sp+20                  cfa[0]
-//     func+22:  sp                     cfa[0]
-//
-// Some things to note here:
-//
-// - Each row describes the state of affairs *before* executing the
-//   instruction at the given address.  Thus, the row for func+0
-//   describes the state before we allocate the stack frame.  In the
-//   next row, the formula for computing the CFA has changed,
-//   reflecting that allocation.
-//
-// - The other entries are written in terms of the CFA; this allows
-//   them to remain unchanged as the stack pointer gets bumped around.
-//   For example, the rule for recovering the return address (the "ra"
-//   column) remains unchanged throughout the function, even as the
-//   stack pointer takes on three different offsets from the return
-//   address.
-//
-// - Although we haven't shown it, most calling conventions designate
-//   "callee-saves" and "caller-saves" registers. The callee must
-//   preserve the values of callee-saves registers; if it uses them,
-//   it must save their original values somewhere, and restore them
-//   before it returns. In contrast, the callee is free to trash
-//   caller-saves registers; if the callee uses these, it will
-//   probably not bother to save them anywhere, and the CFI will
-//   probably mark their values as "unrecoverable".
-//
-//   (However, since the caller cannot assume the callee was going to
-//   save them, caller-saves registers are probably dead in the caller
-//   anyway, so compilers usually don't generate CFA for caller-saves
-//   registers.)
-// 
-// - Exactly where the CFA points is a matter of convention that
-//   depends on the architecture and ABI in use. In the example, the
-//   CFA is the value the stack pointer had upon entry to the
-//   function, pointing at the saved return address. But on the x86,
-//   the call frame information generated by GCC follows the
-//   convention that the CFA is the address *after* the saved return
-//   address.
-//
-//   But by definition, the CFA remains constant throughout the
-//   lifetime of the frame. This makes it a useful value for other
-//   columns to refer to. It is also gives debuggers a useful handle
-//   for identifying a frame.
-//
-// If you look at the table above, you'll notice that a given entry is
-// often the same as the one immediately above it: most instructions
-// change only one or two aspects of the stack frame, if they affect
-// it at all. The DWARF format takes advantage of this fact, and
-// reduces the size of the data by mentioning only the addresses and
-// columns at which changes take place. So for the above, DWARF CFI
-// data would only actually mention the following:
-// 
-//     insn      cfa    r0      r1 ...  ra
-//     =======================================
-//     func+0:   sp                     cfa[0]
-//     func+1:   sp+16
-//     func+2:          cfa[-4]
-//     func+11:  sp+20
-//     func+21:         r0
-//     func+22:  sp            
-//
-// In fact, this is the way the parser reports CFI to the consumer: as
-// a series of statements of the form, "At address X, column Y changed
-// to Z," and related conventions for describing the initial state.
-//
-// Naturally, it would be impractical to have to scan the entire
-// program's CFI, noting changes as we go, just to recover the
-// unwinding rules in effect at one particular instruction. To avoid
-// this, CFI data is grouped into "entries", each of which covers a
-// specified range of addresses and begins with a complete statement
-// of the rules for all recoverable registers at that starting
-// address. Each entry typically covers a single function.
-//
-// Thus, to compute the contents of a given row of the table --- that
-// is, rules for recovering the CFA, RA, and registers at a given
-// instruction --- the consumer should find the entry that covers that
-// instruction's address, start with the initial state supplied at the
-// beginning of the entry, and work forward until it has processed all
-// the changes up to and including those for the present instruction.
-//
-// There are seven kinds of rules that can appear in an entry of the
-// table:
-//
-// - "undefined": The given register is not preserved by the callee;
-//   its value cannot be recovered.
-//
-// - "same value": This register has the same value it did in the callee.
-//
-// - offset(N): The register is saved at offset N from the CFA.
-//
-// - val_offset(N): The value the register had in the caller is the
-//   CFA plus offset N. (This is usually only useful for describing
-//   the stack pointer.)
-//
-// - register(R): The register's value was saved in another register R.
-//
-// - expression(E): Evaluating the DWARF expression E using the
-//   current frame's registers' values yields the address at which the
-//   register was saved.
-//
-// - val_expression(E): Evaluating the DWARF expression E using the
-//   current frame's registers' values yields the value the register
-//   had in the caller.
-
-class CallFrameInfo {
- public:
-  // The different kinds of entries one finds in CFI. Used internally,
-  // and for error reporting.
-  enum EntryKind { kUnknown, kCIE, kFDE, kTerminator };
-
-  // The handler class to which the parser hands the parsed call frame
-  // information.  Defined below.
-  class Handler;
-
-  // A reporter class, which CallFrameInfo uses to report errors
-  // encountered while parsing call frame information.  Defined below.
-  class Reporter;
-
-  // Create a DWARF CFI parser. BUFFER points to the contents of the
-  // .debug_frame section to parse; BUFFER_LENGTH is its length in bytes.
-  // REPORTER is an error reporter the parser should use to report
-  // problems. READER is a ByteReader instance that has the endianness and
-  // address size set properly. Report the data we find to HANDLER.
-  //
-  // This class can also parse Linux C++ exception handling data, as found
-  // in '.eh_frame' sections. This data is a variant of DWARF CFI that is
-  // placed in loadable segments so that it is present in the program's
-  // address space, and is interpreted by the C++ runtime to search the
-  // call stack for a handler interested in the exception being thrown,
-  // actually pop the frames, and find cleanup code to run.
-  //
-  // There are two differences between the call frame information described
-  // in the DWARF standard and the exception handling data Linux places in
-  // the .eh_frame section:
-  //
-  // - Exception handling data uses uses a different format for call frame
-  //   information entry headers. The distinguished CIE id, the way FDEs
-  //   refer to their CIEs, and the way the end of the series of entries is
-  //   determined are all slightly different.
-  //
-  //   If the constructor's EH_FRAME argument is true, then the
-  //   CallFrameInfo parses the entry headers as Linux C++ exception
-  //   handling data. If EH_FRAME is false or omitted, the CallFrameInfo
-  //   parses standard DWARF call frame information.
-  //
-  // - Linux C++ exception handling data uses CIE augmentation strings
-  //   beginning with 'z' to specify the presence of additional data after
-  //   the CIE and FDE headers and special encodings used for addresses in
-  //   frame description entries.
-  //
-  //   CallFrameInfo can handle 'z' augmentations in either DWARF CFI or
-  //   exception handling data if you have supplied READER with the base
-  //   addresses needed to interpret the pointer encodings that 'z'
-  //   augmentations can specify. See the ByteReader interface for details
-  //   about the base addresses. See the CallFrameInfo::Handler interface
-  //   for details about the additional information one might find in
-  //   'z'-augmented data.
-  //
-  // Thus:
-  //
-  // - If you are parsing standard DWARF CFI, as found in a .debug_frame
-  //   section, you should pass false for the EH_FRAME argument, or omit
-  //   it, and you need not worry about providing READER with the
-  //   additional base addresses.
-  //
-  // - If you want to parse Linux C++ exception handling data from a
-  //   .eh_frame section, you should pass EH_FRAME as true, and call
-  //   READER's Set*Base member functions before calling our Start method.
-  //
-  // - If you want to parse DWARF CFI that uses the 'z' augmentations
-  //   (although I don't think any toolchain ever emits such data), you
-  //   could pass false for EH_FRAME, but call READER's Set*Base members.
-  //
-  // The extensions the Linux C++ ABI makes to DWARF for exception
-  // handling are described here, rather poorly:
-  // http://refspecs.linux-foundation.org/LSB_4.0.0/LSB-Core-generic/LSB-Core-generic/dwarfext.html
-  // http://refspecs.linux-foundation.org/LSB_4.0.0/LSB-Core-generic/LSB-Core-generic/ehframechpt.html
-  // 
-  // The mechanics of C++ exception handling, personality routines,
-  // and language-specific data areas are described here, rather nicely:
-  // http://www.codesourcery.com/public/cxx-abi/abi-eh.html
-  CallFrameInfo(const char *buffer, size_t buffer_length,
-                ByteReader *reader, Handler *handler, Reporter *reporter,
-                bool eh_frame = false)
-      : buffer_(buffer), buffer_length_(buffer_length),
-        reader_(reader), handler_(handler), reporter_(reporter),
-        eh_frame_(eh_frame) { }
-
-  ~CallFrameInfo() { }
-
-  // Parse the entries in BUFFER, reporting what we find to HANDLER.
-  // Return true if we reach the end of the section successfully, or
-  // false if we encounter an error.
-  bool Start();
-
-  // Return the textual name of KIND. For error reporting.
-  static const char *KindName(EntryKind kind);
-
- private:
-
-  struct CIE;
-
-  // A CFI entry, either an FDE or a CIE.
-  struct Entry {
-    // The starting offset of the entry in the section, for error
-    // reporting.
-    size_t offset;
-
-    // The start of this entry in the buffer.
-    const char *start;
-    
-    // Which kind of entry this is.
-    //
-    // We want to be able to use this for error reporting even while we're
-    // in the midst of parsing. Error reporting code may assume that kind,
-    // offset, and start fields are valid, although kind may be kUnknown.
-    EntryKind kind;
-
-    // The end of this entry's common prologue (initial length and id), and
-    // the start of this entry's kind-specific fields.
-    const char *fields;
-
-    // The start of this entry's instructions.
-    const char *instructions;
-
-    // The address past the entry's last byte in the buffer. (Note that
-    // since offset points to the entry's initial length field, and the
-    // length field is the number of bytes after that field, this is not
-    // simply buffer_ + offset + length.)
-    const char *end;
-
-    // For both DWARF CFI and .eh_frame sections, this is the CIE id in a
-    // CIE, and the offset of the associated CIE in an FDE.
-    uint64 id;
-
-    // The CIE that applies to this entry, if we've parsed it. If this is a
-    // CIE, then this field points to this structure.
-    CIE *cie;
-  };
-
-  // A common information entry (CIE).
-  struct CIE: public Entry {
-    uint8 version;                      // CFI data version number
-    string augmentation;                // vendor format extension markers
-    uint64 code_alignment_factor;       // scale for code address adjustments 
-    int data_alignment_factor;          // scale for stack pointer adjustments
-    unsigned return_address_register;   // which register holds the return addr
-
-    // True if this CIE includes Linux C++ ABI 'z' augmentation data.
-    bool has_z_augmentation;
- 
-    // Parsed 'z' augmentation data. These are meaningful only if
-    // has_z_augmentation is true.
-    bool has_z_lsda;                    // The 'z' augmentation included 'L'.
-    bool has_z_personality;             // The 'z' augmentation included 'P'.
-    bool has_z_signal_frame;            // The 'z' augmentation included 'S'.
-
-    // If has_z_lsda is true, this is the encoding to be used for language-
-    // specific data area pointers in FDEs.
-    DwarfPointerEncoding lsda_encoding;
-
-    // If has_z_personality is true, this is the encoding used for the
-    // personality routine pointer in the augmentation data.
-    DwarfPointerEncoding personality_encoding;
-
-    // If has_z_personality is true, this is the address of the personality
-    // routine --- or, if personality_encoding & DW_EH_PE_indirect, the
-    // address where the personality routine's address is stored.
-    uint64 personality_address;
-
-    // This is the encoding used for addresses in the FDE header and
-    // in DW_CFA_set_loc instructions. This is always valid, whether
-    // or not we saw a 'z' augmentation string; its default value is
-    // DW_EH_PE_absptr, which is what normal DWARF CFI uses.
-    DwarfPointerEncoding pointer_encoding;
-  };
-
-  // A frame description entry (FDE).
-  struct FDE: public Entry {
-    uint64 address;                     // start address of described code
-    uint64 size;                        // size of described code, in bytes
-
-    // If cie->has_z_lsda is true, then this is the language-specific data
-    // area's address --- or its address's address, if cie->lsda_encoding
-    // has the DW_EH_PE_indirect bit set.
-    uint64 lsda_address;
-  };
-
-  // Internal use.
-  class Rule;
-  class UndefinedRule;
-  class SameValueRule;
-  class OffsetRule;
-  class ValOffsetRule;
-  class RegisterRule;
-  class ExpressionRule;
-  class ValExpressionRule;
-  class RuleMap;
-  class State;
-  
-  // Parse the initial length and id of a CFI entry, either a CIE, an FDE,
-  // or a .eh_frame end-of-data mark. CURSOR points to the beginning of the
-  // data to parse. On success, populate ENTRY as appropriate, and return
-  // true. On failure, report the problem, and return false. Even if we
-  // return false, set ENTRY->end to the first byte after the entry if we
-  // were able to figure that out, or NULL if we weren't.
-  bool ReadEntryPrologue(const char *cursor, Entry *entry);
-
-  // Parse the fields of a CIE after the entry prologue, including any 'z'
-  // augmentation data. Assume that the 'Entry' fields of CIE are
-  // populated; use CIE->fields and CIE->end as the start and limit for
-  // parsing. On success, populate the rest of *CIE, and return true; on
-  // failure, report the problem and return false.
-  bool ReadCIEFields(CIE *cie);
-
-  // Parse the fields of an FDE after the entry prologue, including any 'z'
-  // augmentation data. Assume that the 'Entry' fields of *FDE are
-  // initialized; use FDE->fields and FDE->end as the start and limit for
-  // parsing. Assume that FDE->cie is fully initialized. On success,
-  // populate the rest of *FDE, and return true; on failure, report the
-  // problem and return false.
-  bool ReadFDEFields(FDE *fde);
-
-  // Report that ENTRY is incomplete, and return false. This is just a
-  // trivial wrapper for invoking reporter_->Incomplete; it provides a
-  // little brevity.
-  bool ReportIncomplete(Entry *entry);
-
-  // Return true if ENCODING has the DW_EH_PE_indirect bit set.
-  static bool IsIndirectEncoding(DwarfPointerEncoding encoding) {
-    return encoding & DW_EH_PE_indirect;
-  }
-
-  // The contents of the DWARF .debug_info section we're parsing.
-  const char *buffer_;
-  size_t buffer_length_;
-
-  // For reading multi-byte values with the appropriate endianness.
-  ByteReader *reader_;
-
-  // The handler to which we should report the data we find.
-  Handler *handler_;
-
-  // For reporting problems in the info we're parsing.
-  Reporter *reporter_;
-
-  // True if we are processing .eh_frame-format data.
-  bool eh_frame_;
-};
-
-// The handler class for CallFrameInfo.  The a CFI parser calls the
-// member functions of a handler object to report the data it finds.
-class CallFrameInfo::Handler {
- public:
-  // The pseudo-register number for the canonical frame address.
-  enum { kCFARegister = -1 };
-
-  Handler() { }
-  virtual ~Handler() { }
-
-  // The parser has found CFI for the machine code at ADDRESS,
-  // extending for LENGTH bytes. OFFSET is the offset of the frame
-  // description entry in the section, for use in error messages.
-  // VERSION is the version number of the CFI format. AUGMENTATION is
-  // a string describing any producer-specific extensions present in
-  // the data. RETURN_ADDRESS is the number of the register that holds
-  // the address to which the function should return.
-  //
-  // Entry should return true to process this CFI, or false to skip to
-  // the next entry.
-  //
-  // The parser invokes Entry for each Frame Description Entry (FDE)
-  // it finds.  The parser doesn't report Common Information Entries
-  // to the handler explicitly; instead, if the handler elects to
-  // process a given FDE, the parser reiterates the appropriate CIE's
-  // contents at the beginning of the FDE's rules.
-  virtual bool Entry(size_t offset, uint64 address, uint64 length,
-                     uint8 version, const string &augmentation,
-                     unsigned return_address) = 0;
-
-  // When the Entry function returns true, the parser calls these
-  // handler functions repeatedly to describe the rules for recovering
-  // registers at each instruction in the given range of machine code.
-  // Immediately after a call to Entry, the handler should assume that
-  // the rule for each callee-saves register is "unchanged" --- that
-  // is, that the register still has the value it had in the caller.
-  // 
-  // If a *Rule function returns true, we continue processing this entry's
-  // instructions. If a *Rule function returns false, we stop evaluating
-  // instructions, and skip to the next entry. Either way, we call End
-  // before going on to the next entry.
-  //
-  // In all of these functions, if the REG parameter is kCFARegister, then
-  // the rule describes how to find the canonical frame address.
-  // kCFARegister may be passed as a BASE_REGISTER argument, meaning that
-  // the canonical frame address should be used as the base address for the
-  // computation. All other REG values will be positive.
-
-  // At ADDRESS, register REG's value is not recoverable.
-  virtual bool UndefinedRule(uint64 address, int reg) = 0;
-
-  // At ADDRESS, register REG's value is the same as that it had in
-  // the caller.
-  virtual bool SameValueRule(uint64 address, int reg) = 0;
-
-  // At ADDRESS, register REG has been saved at offset OFFSET from
-  // BASE_REGISTER.
-  virtual bool OffsetRule(uint64 address, int reg,
-                          int base_register, long offset) = 0;
-
-  // At ADDRESS, the caller's value of register REG is the current
-  // value of BASE_REGISTER plus OFFSET. (This rule doesn't provide an
-  // address at which the register's value is saved.)
-  virtual bool ValOffsetRule(uint64 address, int reg,
-                             int base_register, long offset) = 0;
-
-  // At ADDRESS, register REG has been saved in BASE_REGISTER. This differs
-  // from ValOffsetRule(ADDRESS, REG, BASE_REGISTER, 0), in that
-  // BASE_REGISTER is the "home" for REG's saved value: if you want to
-  // assign to a variable whose home is REG in the calling frame, you
-  // should put the value in BASE_REGISTER.
-  virtual bool RegisterRule(uint64 address, int reg, int base_register) = 0;
-
-  // At ADDRESS, the DWARF expression EXPRESSION yields the address at
-  // which REG was saved.
-  virtual bool ExpressionRule(uint64 address, int reg,
-                              const string &expression) = 0;
-
-  // At ADDRESS, the DWARF expression EXPRESSION yields the caller's
-  // value for REG. (This rule doesn't provide an address at which the
-  // register's value is saved.)
-  virtual bool ValExpressionRule(uint64 address, int reg,
-                                 const string &expression) = 0;
-
-  // Indicate that the rules for the address range reported by the
-  // last call to Entry are complete.  End should return true if
-  // everything is okay, or false if an error has occurred and parsing
-  // should stop.
-  virtual bool End() = 0;
-
-  // Handler functions for Linux C++ exception handling data. These are
-  // only called if the data includes 'z' augmentation strings.
-
-  // The Linux C++ ABI uses an extension of the DWARF CFI format to
-  // walk the stack to propagate exceptions from the throw to the
-  // appropriate catch, and do the appropriate cleanups along the way.
-  // CFI entries used for exception handling have two additional data
-  // associated with them:
-  //
-  // - The "language-specific data area" describes which exception
-  //   types the function has 'catch' clauses for, and indicates how
-  //   to go about re-entering the function at the appropriate catch
-  //   clause. If the exception is not caught, it describes the
-  //   destructors that must run before the frame is popped.
-  //
-  // - The "personality routine" is responsible for interpreting the
-  //   language-specific data area's contents, and deciding whether
-  //   the exception should continue to propagate down the stack,
-  //   perhaps after doing some cleanup for this frame, or whether the
-  //   exception will be caught here.
-  //
-  // In principle, the language-specific data area is opaque to
-  // everybody but the personality routine. In practice, these values
-  // may be useful or interesting to readers with extra context, and
-  // we have to at least skip them anyway, so we might as well report
-  // them to the handler.
-
-  // This entry's exception handling personality routine's address is
-  // ADDRESS. If INDIRECT is true, then ADDRESS is the address at
-  // which the routine's address is stored. The default definition for
-  // this handler function simply returns true, allowing parsing of
-  // the entry to continue.
-  virtual bool PersonalityRoutine(uint64 address, bool indirect) {
-    return true;
-  }
-
-  // This entry's language-specific data area (LSDA) is located at
-  // ADDRESS. If INDIRECT is true, then ADDRESS is the address at
-  // which the area's address is stored. The default definition for
-  // this handler function simply returns true, allowing parsing of
-  // the entry to continue.
-  virtual bool LanguageSpecificDataArea(uint64 address, bool indirect) {
-    return true;
-  }
-
-  // This entry describes a signal trampoline --- this frame is the
-  // caller of a signal handler. The default definition for this
-  // handler function simply returns true, allowing parsing of the
-  // entry to continue.
-  //
-  // The best description of the rationale for and meaning of signal
-  // trampoline CFI entries seems to be in the GCC bug database:
-  // http://gcc.gnu.org/bugzilla/show_bug.cgi?id=26208
-  virtual bool SignalHandler() { return true; }
-};
-
-// The CallFrameInfo class makes calls on an instance of this class to
-// report errors or warn about problems in the data it is parsing. The
-// default definitions of these methods print a message to stderr, but
-// you can make a derived class that overrides them.
-class CallFrameInfo::Reporter {
- public:
-  // Create an error reporter which attributes troubles to the section
-  // named SECTION in FILENAME.
-  //
-  // Normally SECTION would be .debug_frame, but the Mac puts CFI data
-  // in a Mach-O section named __debug_frame. If we support
-  // Linux-style exception handling data, we could be reading an
-  // .eh_frame section.
-  Reporter(const string &filename,
-           const string &section = ".debug_frame")
-      : filename_(filename), section_(section) { }
-  virtual ~Reporter() { }
-
-  // The CFI entry at OFFSET ends too early to be well-formed. KIND
-  // indicates what kind of entry it is; KIND can be kUnknown if we
-  // haven't parsed enough of the entry to tell yet.
-  virtual void Incomplete(uint64 offset, CallFrameInfo::EntryKind kind);
-
-  // The .eh_frame data has a four-byte zero at OFFSET where the next
-  // entry's length would be; this is a terminator. However, the buffer
-  // length as given to the CallFrameInfo constructor says there should be
-  // more data.
-  virtual void EarlyEHTerminator(uint64 offset);
-
-  // The FDE at OFFSET refers to the CIE at CIE_OFFSET, but the
-  // section is not that large.
-  virtual void CIEPointerOutOfRange(uint64 offset, uint64 cie_offset);
-
-  // The FDE at OFFSET refers to the CIE at CIE_OFFSET, but the entry
-  // there is not a CIE.
-  virtual void BadCIEId(uint64 offset, uint64 cie_offset);
-
-  // The FDE at OFFSET refers to a CIE with version number VERSION,
-  // which we don't recognize. We cannot parse DWARF CFI if it uses
-  // a version number we don't recognize.
-  virtual void UnrecognizedVersion(uint64 offset, int version);
-
-  // The FDE at OFFSET refers to a CIE with augmentation AUGMENTATION,
-  // which we don't recognize. We cannot parse DWARF CFI if it uses
-  // augmentations we don't recognize.
-  virtual void UnrecognizedAugmentation(uint64 offset,
-                                        const string &augmentation);
-
-  // The pointer encoding ENCODING, specified by the CIE at OFFSET, is not
-  // a valid encoding.
-  virtual void InvalidPointerEncoding(uint64 offset, uint8 encoding);
-
-  // The pointer encoding ENCODING, specified by the CIE at OFFSET, depends
-  // on a base address which has not been supplied.
-  virtual void UnusablePointerEncoding(uint64 offset, uint8 encoding);
-
-  // The CIE at OFFSET contains a DW_CFA_restore instruction at
-  // INSN_OFFSET, which may not appear in a CIE.
-  virtual void RestoreInCIE(uint64 offset, uint64 insn_offset);
-
-  // The entry at OFFSET, of kind KIND, has an unrecognized
-  // instruction at INSN_OFFSET.
-  virtual void BadInstruction(uint64 offset, CallFrameInfo::EntryKind kind,
-                              uint64 insn_offset);
-
-  // The instruction at INSN_OFFSET in the entry at OFFSET, of kind
-  // KIND, establishes a rule that cites the CFA, but we have not
-  // established a CFA rule yet.
-  virtual void NoCFARule(uint64 offset, CallFrameInfo::EntryKind kind, 
-                         uint64 insn_offset);
-
-  // The instruction at INSN_OFFSET in the entry at OFFSET, of kind
-  // KIND, is a DW_CFA_restore_state instruction, but the stack of
-  // saved states is empty.
-  virtual void EmptyStateStack(uint64 offset, CallFrameInfo::EntryKind kind, 
-                               uint64 insn_offset);
-
-  // The DW_CFA_remember_state instruction at INSN_OFFSET in the entry
-  // at OFFSET, of kind KIND, would restore a state that has no CFA
-  // rule, whereas the current state does have a CFA rule. This is
-  // bogus input, which the CallFrameInfo::Handler interface doesn't
-  // (and shouldn't) have any way to report.
-  virtual void ClearingCFARule(uint64 offset, CallFrameInfo::EntryKind kind, 
-                               uint64 insn_offset);
-
- protected:
-  // The name of the file whose CFI we're reading.
-  string filename_;
-
-  // The name of the CFI section in that file.
-  string section_;
-};
-
-}  // namespace dwarf2reader
-
-#endif  // UTIL_DEBUGINFO_DWARF2READER_H__