NAME

dwarf_init, dwarf_elf_init —

allocate a DWARF debug descriptor

LIBRARY

DWARF Access Library (libdwarf, -ldwarf)

SYNOPSIS

#include <libdwarf.h>

int
dwarf_init(int fd, int mode, Dwarf_Handler errhand, Dwarf_Ptr errarg, Dwarf_Debug *ret, Dwarf_Error *err);

in
dwarf_elf_init(Elf *elf, int mode, Dwarf_Handler errhand, Dwarf_Ptr errarg, Dwarf_Debug *ret, Dwarf_Error *err);

DESCRIPTION

These functions allocate and return a Dwarf_Debug instance for the object denoted by argument fd or elf. This instance would be used for subsequent access to debugging information in the object by other functions in the DWARF(3) library.

For function dwarf_init(), argument fd denotes an open file descriptor referencing a compilation object. Function dwarf_init() implicitly allocates an Elf descriptor for argument fd.

For function dwarf_elf_init(), argument elf denotes a descriptor returned by elf_begin(3) or elf_memory(3).

Argument mode specifies the access mode desired. It should be at least as permissive as the mode with which the file descriptor fd or the ELF descriptor elf was created with. Legal values for argument mode are:

DW_DLC_RDWR: Permit reading and writing of DWARF information.
DW_DLC_READ: Operate in read-only mode.
DW_DLC_WRITE: Permit writing of DWARF information.

Argument errhand denotes 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 scheme used by the DWARF(3) library.

Argument errarg is passed to the error handler function denoted by argument errhand when it is invoked.

Argument ret points to the memory location that will hold a Dwarf_Debug reference on a successful call these functions.

Argument err references a memory location that would hold a Dwarf_Error descriptor in case of an error.

Memory Management

The Dwarf_Debug instance returned by these functions should be freed using dwarf_finish().

IMPLEMENTATION NOTES

The current implementation does not support access modes DW_DLC_RDWR and DW_DLC_WRITE.

RETURN VALUES

These functions return the following values:

[DW_DLV_OK]: This return value indicates a successful return.
[DW_DLV_ERROR]: The operation failed.
[DW_DLV_NO_ENTRY]: The object specified by arguments fd or elf did not contain debug information.

EXAMPLES

To initialize a Dwarf_Debug instance from a open file descriptor referencing an ELF object, and with the default error handler, use:

Dwarf_Error err;
Dwarf_Debug dbg;

if (dwarf_init(fd, DW_DLC_READ, NULL, NULL, &dbg, &err) !=
    DW_DLV_OK)
	errx(EXIT_FAILURE, "dwarf_init: %s", dwarf_errmsg(err));