dwarf —
access debugging information in object files
DWARF Access Library (libdwarf, -ldwarf)
The DWARF Access Library (libdwarf, -ldwarf) provides
  functions that allow an application to read and write debugging information in
  object files. The format of debugging information accessible through this API
  is defined by the DWARF standard, see
  dwarf(4).
The DWARF(3) API has
    two parts:
  - A consumer API set allows applications to read existing debug information
      in a program object. The functions that comprise the DWARF consumer API
      are described in the section
      DWARF Consumer API
    below.
- A producer API set that allows applications to add debug information to a
      program object. The functions that comprise the DWARF producer API are
      described in the section DWARF
      Producer API below.
Each function referenced below is further described in its own
    manual page.
The DWARF library uses the following prefixes:
  - DWARF_*
- Used for error numbers and constants.
- DW_*
- Used for constants.
- Dwarf_*
- Used for types.
- dwarf_*
- Used for functions and macros that make up the API.
The DWARF(3) API uses the following data types:
  - Dwarf_Abbrev
- Describes DWARF abbreviations.
- Dwarf_Addr
- A program address in the target object.
- Dwarf_Arange
- Describes address ranges.
- Dwarf_Attribute,
    Dwarf_P_Attribute
- Describes attributes of debugging information entries.
- Dwarf_Bool
- Used for boolean states.
- Dwarf_Cie, Dwarf_P_Cie
- Describes call information that is common to several frames.
- Dwarf_Debug,
    Dwarf_P_Debug
- An opaque type describing a debug context.
- Dwarf_Die, Dwarf_P_Die
- A debugging information entry.
- Dwarf_Fde, Dwarf_P_Fde
- A frame descriptor.
- Dwarf_Func
- A descriptor representing a function.
- Dwarf_Global
- A descriptor representing a global name.
- Dwarf_Half
- A 16-bit wide unsigned numeric type.
- Dwarf_Handler
- A pointer to an error handling function.
- Dwarf_Line
- A descriptor for a source line.
- Dwarf_Off
- An unsigned file offset.
- Dwarf_P_Expr
- A descriptor for a location expression.
- Dwarf_Ptr
- A virtual address used by an application.
- Dwarf_Signed
- A 64-bit wide signed numeric type.
- Dwarf_Small
- An 8-bit wide unsigned numeric type.
- Dwarf_Type
- A descriptor representing a user-specified type.
- Dwarf_Unsigned
- A 64-bit wide unsigned numeric type.
- Dwarf_Var
- A descriptor representing a static variable.
- Dwarf_Weak
- A descriptor representing a weak name.
Library functions that encounter an error will return with a value other thanDW_DLV_OK.
The DWARF Access Library (libdwarf,
    -ldwarf) allows applications to specify three levels of error
    handling:
  - Most library functions take a parameter of type
      Dwarf_Error that specifies a location to store an
      error descriptor in case of an error. If an error occurs during the
      execution on an API, and if this parameter is
      non-NULL, then an error
      descriptor is written to the location specified.
- Otherwise, if the error parameter was NULL, but if
      an error handler was defined for the debug context in use using
      dwarf_init(3) or
      dwarf_seterrhand(3),
      then the library will invoke the specified error handler with an error
      descriptor as argument.
- Otherwise, if a library wide error handler was specified using
      dwarf_seterrhand(3),
      it is called.
Error descriptors may be used with
    dwarf_errmsg(3) or
    dwarf_errno(3).
The DWARF consumer API permits applications to read DWARF information in an
  object file.
The major functional groups of functions in the consumer API are
    listed below.
  - Abbreviations
- 
    
      - dwarf_get_abbrev()
- Retrieve abbreviation information at a given offset.
- dwarf_get_abbrev_children_flag()
- Check if an abbreviation has child elements.
- dwarf_get_abbrev_code()
- Retrieve the abbreviation code for an abbreviation entry
        descriptor.
- dwarf_get_abbrev_entry()
- Retrieve abbreviation information for an abbreviation entry
          descriptor.
- dwarf_get_abbrev_tag()
- Retrieve the tag for an abbreviation entry.
 
- Addresses
- 
    
      - dwarf_get_address_size()
- Return the number of bytes needed to represent an address.
- dwarf_get_arange()
- Search for an address range descriptor covering an address.
- dwarf_get_arange_cu_header_offset()
- Retrieve the offsets associated with an address range descriptor.
- dwarf_get_arange_info()
- Extract address range information from a descriptor.
- dwarf_get_aranges()
- Retrieve program address space mappings.
- dwarf_get_cu_die_offset()
- Retrieve the offset associated with a compilation unit for an address
          range descriptor.
- dwarf_get_ranges(),- dwarf_get_ranges_a()
- Retrieve information about non-contiguous address ranges for a
          debugging information entry.
 
- Attributes
- 
    
      - dwarf_arrayorder()
- Retrieve the value of a DW_AT_orderingattribute.
- dwarf_attr()
- Retrieve an attribute descriptor.
- dwarf_attrlist()
- Retrieve attribute descriptors for a debugging information entry.
- dwarf_attroffset()
- Retrieve the section-relative offset of an attribute descriptor.
- dwarf_attrval_flag()
- Retrieve a DW_AT_FORM_flagvalue.
- dwarf_attrval_signed()
- Retrieve an attribute's value as a signed integral quantity.
- dwarf_attrval_string()
- Retrieve an attribute's value as a NUL-terminated string.
- dwarf_attrval_unsigned()
- Retrieve an attribute's value as an unsigned integral quantity.
- dwarf_bitoffset(),
- Retrieve the value of a DW_AT_bit_offsetattribute.
- dwarf_bitsize(),
- Retrieve the value of a DW_AT_bit_sizeattribute.
- dwarf_bytesize()
- Retrieve the value of a DW_AT_byte_sizeattribute.
- dwarf_formaddr()
- Return the value of an ADDRESS-class
          attribute.
- dwarf_formblock()
- Return the value of a BLOCK-class
        attribute
- dwarf_formexprloc()
- Return information about a location expression.
- dwarf_formflag()
- Retrieve information about a BOOLEAN-class
          attribute.
- dwarf_formref(),- dwarf_global_formref()
- Retrieve offsets for REFERENCE-class
          attributes.
- dwarf_formsdata(),- dwarf_formudata()
- Retrieve the value of a CONSTANT-class
          attribute.
- dwarf_formsig8()
- Return the type signature for a DWARF type.
- dwarf_formstring()
- Retrieve information about a STRING-class
          attribute.
- dwarf_get_form_class()
- Retrieve the form class for an attribute.
- dwarf_hasattr()
- Check for the presence of an attribute.
- dwarf_hasform()
- Check if an attribute has the given form.
- dwarf_whatattr()
- Retrieve the attribute code for an attribute.
- dwarf_whatform(),- dwarf_whatform_direct()
- Retrieve the form of an attribute.
 
- Call Information Entries and Frame Descriptor Entries
- 
    
      - dwarf_get_cie_index()
- Retrieve the index for a CIE descriptor.
- dwarf_get_cie_info()
- Retrieve information from a CIE descriptor.
- dwarf_get_cie_of_fde()
- Retrieve a CIE descriptor.
- dwarf_get_fde_at_pc()
- Retrieve an FDE descriptor for an address.
- dwarf_get_fde_info_for_all_regs()
- Retrieve register rule row.
- dwarf_get_fde_info_for_all_regs3()
- Retrieve register rule row (revised API).
- dwarf_get_fde_info_for_cfa_reg3()
- Retrieve a CFA register rule.
- dwarf_get_fde_info_for_reg()
- Retrieve a register rule.
- dwarf_get_fde_info_for_reg3()
- Retrieve a register rule (revised API).
- dwarf_get_fde_instr_bytes()
- Retrieve instructions from an FDE descriptor.
- dwarf_get_fde_list(),- dwarf_get_fde_list_eh()
- Retrieve frame information.
- dwarf_get_fde_n()
- Retrieve an FDE descriptor.
- dwarf_get_fde_range()
- Retrieve range information from an FDE descriptor.
 
- Compilation Units
- 
    
      - dwarf_get_cu_die_offset_given_cu_header_offset(),- dwarf_get_cu_die_offset_given_cu_header_offset_b()
- Retrieve the offset of the debugging information entry for a
          compilation or type unit.
- dwarf_next_cu_header(),- dwarf_next_cu_header_b(),- dwarf_next_cu_header_c()
- Step through compilation units in a debug context.
 
- Debugging Information Entries
- 
    
      - dwarf_child()
- Returns the child of a debugging information entry.
- dwarf_die_abbrev_code()
- Returns the abbreviation code for a debugging information entry.
- dwarf_die_CU_offset(),- dwarf_die_CU_offset_range()
- Retrieve offsets and lengths for a compilation unit.
- dwarf_diename()
- Returns the DW_AT_nameattribute for a
          debugging information entry.
- dwarf_dieoffset()
- Retrieves the offset for a debugging information entry.
- dwarf_get_die_infotypes_flag()
- Indicate the originating section for a debugging information
        entry.
- dwarf_highpc(),- dwarf_highpc_b()
- Return the highest PC value for a debugging information entry.
- dwarf_lowpc()
- Return the lowest PC value for a debugging information entry.
- dwarf_offdie(),- dwarf_offdie_b()
- Retrieve a debugging information entry given an offset.
- dwarf_siblingof(),- dwarf_siblingof_b()
- Retrieve the sibling descriptor for a debugging information
        entry.
- dwarf_srclang()
- Retrieve the source language attribute for a debugging information
          entry.
- dwarf_tag()
- Retrieve the tag for a debugging information entry.
 
- Functions
- 
    
      - dwarf_func_cu_offset()
- Retrieves the offset for the compilation unit for a function.
- dwarf_func_die_offset()
- Retrieves the offset for the debugging information entry for a
          function.
- dwarf_funcname()
- Retrieves the name of a function.
- dwarf_func_name_offsets()
- Retrieve both the name and offsets for a function.
- dwarf_get_funcs()
- Retrieve information about static functions.
 
- Globals
- 
    
      - dwarf_get_globals()
- Retrieve a list of globals.
- dwarf_global_cu_offset()
- Return the offset for compilation unit for a global.
- dwarf_global_die_offset()
- Return the offset for the debugging information entry for a
        global.
- dwarf_global_name_offsets()
- Return the name and offsets for a global.
- dwarf_globname()
- Return the name for a global.
 
- Initialization and Finalization
- Functions dwarf_elf_init() anddwarf_init() may be used for initialization. The
      functiondwarf_finish() may be used to release
      resources.The functions dwarf_object_init() anddwarf_object_finish() allow an application to
        specify alternate low-level file access routines.
 
- Line Numbers
- 
    
      - dwarf_lineaddr()
- Retrieve the program address for a source line.
- dwarf_linebeginstatement()
- Check if a source line corresponds to the beginning of a
        statement.
- dwarf_lineblock()
- Check if a source line corresponds to the start of a basic block.
- dwarf_lineendsequence()
- Check if the source line corresponds to the end of a sequence of
          instructions.
- dwarf_lineno()
- Retrieve the line number for a line descriptor.
- dwarf_lineoff()
- Retrieve the column number for a line descriptor.
- dwarf_linesrc()
- Retrieve the source file for a line descriptor.
- dwarf_line_srcfileno()
- Retrieve the index of the source file for a line descriptor.
- dwarf_srcfiles()
- Retrieve source files for a compilation unit.
- dwarf_srclines()
- Return line number information for a compilation unit.
 
- Location Lists
- 
    
      - dwarf_get_loclist_entry()
- Retrieve a location list entry.
- dwarf_loclist(),- dwarf_loclist_n()
- Retrieve location expressions.
- dwarf_loclist_from_expr(),- dwarf_loclist_from_expr_a(),- dwarf_loclist_from_expr_b()
- Translate a location expression into a location descriptor.
 
- Error Handling
- 
    
      - dwarf_errmsg()
- Retrieve a human-readable error message.
- dwarf_errno()
- Retrieve an error number from an error descriptor.
- dwarf_seterrarg()
- Set the argument passed to a callback error handler.
- dwarf_seterrhand()
- Set the callback handler to be called in case of an error.
 
- Frame Handling
- 
    
      - dwarf_expand_frame_instructions()
- Translate frame instruction bytes.
- dwarf_set_frame_cfa_value()
- Set the CFA parameter for the internal register rule table.
- dwarf_set_frame_rule_initial_value()
- Set the initial value of the register rules in the internal register
          rule table.
- dwarf_set_frame_rule_table_size()
- Set the maximum number of columns in the register rule table.
- dwarf_set_frame_same_value()
- Set the register number representing the “same value”
          rule.
- dwarf_set_frame_undefined_value()
- Set the register number representing the “undefined”
          rule.
 
- Macros
- 
    
      - dwarf_find_macro_value_start()
- Return the macro value part of a macro string.
- dwarf_get_macro_details()
- Retrieve macro information.
 
- Memory Management
- In the DWARF consumer API, the rules for memory management differ between
      functions. In some cases, the memory areas returned to the application by
      the library are freed by calling specific API functions. In others, the
      deallocation function dwarf_dealloc() suffices.
      The individual manual pages for the API's functions document the specific
      memory management rules to be followed.The function dwarf_dealloc() is used
        to mark memory arenas as unused. Additionally, the following functions
        release specific types of DWARF resources:dwarf_fde_cie_list_dealloc(),dwarf_funcs_dealloc(),dwarf_globals_dealloc(),dwarf_pubtypes_dealloc(),dwarf_ranges_dealloc(),dwarf_srclines_dealloc(),dwarf_types_dealloc(),dwarf_vars_dealloc(), anddwarf_weaks_dealloc().
 
- Symbol Constants
- The following functions may be used to return symbolic names for DWARF
      constants: dwarf_get_ACCESS_name(),dwarf_get_AT_name(),dwarf_get_ATE_name(),dwarf_get_CC_name(),dwarf_get_CFA_name(),dwarf_get_CHILDREN_name(),dwarf_get_DS_name(),dwarf_get_DSC_name(),dwarf_get_EH_name(),dwarf_get_END_name(),dwarf_get_FORM_name(),dwarf_get_ID_name(),dwarf_get_INL_name(),dwarf_get_LANG_name(),dwarf_get_LNE_name(),dwarf_get_LNS_name(),dwarf_get_MACINFO_name(),dwarf_get_OP_name(),dwarf_get_ORD_name(),dwarf_get_TAG_name(),dwarf_get_VIRTUALITY_name(), anddwarf_get_VIS_name().
- Types
- 
    
      - dwarf_get_pubtypes(),- dwarf_get_types()
- Retrieve descriptors for user-defined types.
- dwarf_next_types_section()
- Step through “.debug_types” sections in a debug
        context.
- dwarf_pubtype_cu_offset(),- dwarf_type_cu_offset()
- Return the offset for the compilation unit for a type.
- dwarf_pubtype_die_offset(),- dwarf_type_die_offset()
- Return the offset for the debugging information entry for a type.
- dwarf_pubtypename(),- dwarf_typename()
- Retrieve the name of a type.
- dwarf_pubtype_name_offsets(),- dwarf_type_name_offsets()
- Retrieve the name and offsets for a type.
 
- Variables
- 
    
      - dwarf_get_vars()
- Retrieve descriptors for static variables.
- dwarf_var_cu_offset()
- Return the offset for the compilation unit for a variable.
- dwarf_var_die_offset()
- Return the offset for the debugging information entry for a
        variable.
- dwarf_varname()
- Retrieve the name of a variable.
- dwarf_var_name_offsets()
- Retrieve the name and offsets for a variable.
 
- Weak Symbols
- 
    
      - dwarf_get_weaks()
- Retrieve information about weak symbols.
- dwarf_weak_cu_offset()
- Return the offset for the compilation unit for a weak symbol.
- dwarf_weak_die_offset()
- Return the offset for the debugging information entry for a weak
          symbol.
- dwarf_weakname()
- Retrieve the name of a weak symbol.
- dwarf_weak_name_offsets()
- Retrieve the name and offsets for a weak symbol.
 
- Miscellaneous
- 
    
      - dwarf_get_elf()
- Retrieve the ELF descriptor for a debug context, see
          elf(3).
- dwarf_get_str()
- Retrieve a NUL-terminated string from the DWARF string section.
- dwarf_set_reloc_application()
- Control whether relocations are to be handled by
          DWARF Access Library (libdwarf, -ldwarf).
 
The DWARF producer API permits applications to add DWARF information to an
  object file.The major functional groups of functions in the producer API are
    listed below.
  - Attribute Management
- The following functions are used to attach attributes to a debugging
      information entry: dwarf_add_AT_comp_dir(),dwarf_add_AT_const_value_signedint(),dwarf_add_AT_const_value_string(),dwarf_add_AT_const_value_unsignedint(),dwarf_add_AT_dataref(),dwarf_add_AT_flag(),dwarf_add_AT_location_expr(),dwarf_add_AT_name(),dwarf_add_AT_producer(),dwarf_add_AT_ref_address(),dwarf_add_AT_reference(),dwarf_add_AT_signed_const(),dwarf_add_AT_string(),dwarf_add_AT_targ_address(),dwarf_add_AT_targ_address_b() anddwarf_add_AT_unsigned_const().
- Debugging Information Entry Management
- 
    
      - dwarf_add_die_to_debug()
- Set the root debugging information entry for a DWARF producer
          instance.
- dwarf_die_link()
- Links debugging information entries.
- dwarf_new_die()
- Allocate a new debugging information entry.
 
- Initialization and Finalization
- The functions dwarf_producer_init() anddwarf_producer_init_b() are used to initialize a
      producer instance.When done, applications release resources using the function
        dwarf_producer_finish().
 
- Relocations and Sections
- 
    
      - dwarf_get_relocation_info()
- Retrieve a relocation array from a producer instance.
- dwarf_get_relocation_info_count()
- Return the number of relocation arrays for a producer instance.
- dwarf_get_section_bytes()
- Retrieve the ELF byte stream for a section.
- dwarf_reset_section_bytes()
- Reset internal state for a producer instance.
- dwarf_transform_to_disk_form()
- Prepare byte streams for writing out.
 
- Macros
- 
    
      - dwarf_def_macro()
- Add a macro definition.
- dwarf_end_macro_file(),- dwarf_start_macro_file()
- Record macro file related information.
- dwarf_undef_macro()
- Note the removal of a macro definition.
- dwarf_vendor_ext()
- Enables storing macro information as specified in the DWARF
        standard.
 
- Symbols, Expressions, Addresses and Offsets
- 
    
      - dwarf_add_arange(),- dwarf_add_arange_b()
- Add address range information.
- dwarf_add_directory_decl()
- Add information about an include directory to a producer
        instance.
- dwarf_add_fde_inst()
- Add an operation to a frame descriptor entry.
- dwarf_add_file_decl()
- Add information about a source file to a producer instance.
- dwarf_add_frame_cie()
- Add call information to a frame descriptor.
- dwarf_add_frame_fde(),- dwarf_add_frame_fde_b()
- Link a frame descriptor to a producer instance.
- dwarf_add_funcname()
- Add information about a function to a producer instance.
- dwarf_add_line_entry()
- Record mapping information between machine addresses and a source
          line.
- dwarf_add_expr_addr(),- dwarf_add_expr_addr_b()
- Add a DW_OP_addropcode to a location
          expression.
- dwarf_add_expr_gen()
- Add an operator to a location expression.
- dwarf_add_pubname()
- Add information about a global name to a producer instance.
- dwarf_add_typename()
- Add information about a type to a producer instance.
- dwarf_add_varname()
- Add information about a static variable to a producer instance.
- dwarf_add_weakname()
- Add information about a weak symbol to a producer instance.
- dwarf_expr_current_offset()
- Retrieve the current size of a location expression.
- dwarf_expr_into_block()
- Convert a location expression into a byte stream.
- dwarf_fde_cfa_offset()
- Append a DW_CFA_offsetoperation to a frame
          descriptor.
- dwarf_lne_end_sequence(),- dwarf_lne_set_address()
- Note address ranges for source lines.
- dwarf_new_expr()
- Allocate a location expression descriptor.
- dwarf_new_fde()
- Allocate a frame descriptor.
 
- Miscellaneous
- The function dwarf_producer_set_isa() sets the
      instruction set architecture for the producer instance.
This implementation is believed to be source compatible with the SGI/GNU
  DWARF(3) library, version 20110113.Known differences with the SGI/GNU library include:
  - The memory management scheme used differs, in a backward-compatible way.
      See Memory Management above,
      for coding guidelines for portable applications.
- There is provision for setting a library-wide error handler in addition to
      the per-debug context handlers supported by the SGI/GNU API, see the
      subsection Error Handling
    above.
The following APIs are extensions specific to this implementation:
  - dwarf_attroffset()
- dwarf_next_types_section()
- dwarf_producer_set_isa()
The DWARF standard is defined by The DWARF
  Debugging Information Format, Version 4,
  http://www.dwarfstd.org/.