DWARF_OBJECT_INIT(3) | Library Functions Manual | DWARF_OBJECT_INIT(3)

# NAME

`dwarf_object_init` —
allocate a DWARF debug descriptor with application-specific file access methods

# LIBRARY

DWARF Access Library (libdwarf, -ldwarf)

# SYNOPSIS

`#include <libdwarf.h>`

int
`dwarf_object_init`(Dwarf_Obj_Access_Interface *iface, Dwarf_Handler errhand, Dwarf_Ptr errarg, Dwarf_Debug *dbg, Dwarf_Error *err);

# DESCRIPTION

The `dwarf_object_init`() function allocates and returns a Dwarf_Debug instance that uses application-supplied access methods to read file content.

The argument iface should point to a populated Dwarf_Obj_Access_Interface structure. The contents of the Dwarf_Obj_Access_Interface structure are described in the section Object Access Functions below.

The argument errhand should point to a function to be called in case of an error. If this argument is `NULL` then a default error handling scheme is used. See dwarf(3) for a description of the error handling schemes available.

The argument errarg will be passed to the error handler function pointed to by argument errhand.

The argument dbg should point to a memory location that will be set to a reference to the returned Dwarf_Debug descriptor.

The argument err will be used to return a Dwarf_Error descriptor in case of an error.

## Object Access Functions

The data structures used to specify object access methods are defined in `<libdwarf.h>`.

Dwarf_Obj_Access_Interface
  This structure bundles together a set of file access methods along with a pointer to application-private state.

      typedef struct {
      	void *object;
      	const Dwarf_Obj_Access_Methods *methods;
      } Dwarf_Obj_Access_Interface;

  object
    This field points to application-specific state that will be passed as the first parameter to the actual access object methods.
  methods
    This structure contains pointers to the functions implementing the access methods, as described below.
Dwarf_Obj_Access_Methods
  This structure specifies the functions implementing low-level access.

      typedef struct {
      	int (*get_section_info)(void *obj, Dwarf_Half index,
      	    Dwarf_Obj_Access_Section *ret, int *error);
      	Dwarf_Endianness (*get_byte_order)(void *obj);
      	Dwarf_Small (*get_length_size)(void *obj);
      	Dwarf_Small (*get_pointer_size)(void *obj);
      	Dwarf_Unsigned (*get_section_count)(void *obj);
      	int (*load_section)(void *obj, Dwarf_Half ndx,
      	    Dwarf_Small **ret_data, int *error);
      } Dwarf_Obj_Access_Methods;

  get_byte_order
    This function should return the endianness of the DWARF object by returning one of the constants `DW_OBJECT_MSB` or `DW_OBJECT_LSB`.
  get_length_size
    This function should return the number of bytes needed to represent a DWARF offset in the object being debugged.
  get_pointer_size
    This function should return the size in bytes, in the object being debugged, of a memory address.
  get_section_count
    This function should return the number of sections in the object being debugged.
  get_section_info
    This function should return information about the section at the index ndx by filling in the structure of type Dwarf_Obj_Access_Section pointed to by argument ret. The Dwarf_Obj_Access_Section structure is described below.
  load_section
    This function should load the section specified by argument ndx into memory and place a pointer to the section's data into the location pointed to by argument ret_data.

  The argument obj passed to these functions will be set to the pointer value in the object field of the associated Dwarf_Obj_Access_Interface structure.

  The argument error is used to return an error code in case of an error.

Dwarf_Obj_Access_Section
  This structure describes the layout of a section in the DWARF object.

      typedef struct {
      	Dwarf_Addr addr;
      	Dwarf_Unsigned size;
      	const char *name;
      } Dwarf_Obj_Access_Section;

  addr
    A pointer to the start of the section's data.
  size
    The size of the section in bytes.
  name
    A pointer to a NUL-terminated string containing the name of the section.

# RETURN VALUES

On success, the `dwarf_object_init`() function returns `DW_DLV_OK`. In case of an error, the function returns `DW_DLV_ERROR` and sets the argument err.

# ERRORS

The `dwarf_object_init`() function may fail with the following errors:

[`DW_DLE_ARGUMENT`]
  One of the arguments iface or dbg was NULL.
[`DW_DLE_DEBUG_INFO_NULL`]
  The underlying object did not contain debugging information.
[`DW_DLE_MEMORY`]
  An out of memory condition was encountered during the execution of the function.

# SEE ALSO

dwarf(3), dwarf_init(3), dwarf_init_elf(3), dwarf_object_finish(3)

September 29, 2011 | NetBSD 9.0