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dwarf_init(3) [freebsd man page]

DWARF_INIT(3)						   BSD Library Functions Manual 					     DWARF_INIT(3)

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(). 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. IMPLEMENTATION NOTES
The current implementation does not support access modes DW_DLC_RDWR and DW_DLC_WRITE. 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)); SEE ALSO
dwarf(3), dwarf_errmsg(3), dwarf_finish(3), dwarf_get_elf(3), elf_begin(3), elf_memory(3) BSD
November 9, 2011 BSD

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DWARF_GET_ABBREV(3)					   BSD Library Functions Manual 				       DWARF_GET_ABBREV(3)

NAME
dwarf_get_abbrev -- retrieve abbreviation information LIBRARY
DWARF Access Library (libdwarf, -ldwarf) SYNOPSIS
#include <libdwarf.h> int dwarf_get_abbrev(Dwarf_Debug dbg, Dwarf_Unsigned offset, Dwarf_Abbrev *ret_abbrev, Dwarf_Unsigned *length, Dwarf_Unsigned *attr_count, Dwarf_Error *err); DESCRIPTION
Function dwarf_get_abbrev() retrieves information about an abbreviation from the DWARF abbreviations section, ``.debug_abbrev''. Abbrevia- tion information is returned using an opaque descriptor of type Dwarf_Abbrev. The returned Dwarf_Abbrev descriptor may then be passed to the other abbreviation related APIs in the DWARF(3) API to retrieve specific information about the abbreviation. Argument dbg should reference a DWARF debug context allocated using dwarf_init(3). Argument offset should be an offset, relative to the ``.debug_abbrev'' section, to the start of an abbreviation entry. Argument ret_abbrev should point to a location that will hold a pointer to the returned Dwarf_Abbrev descriptor. Argument length should point to a location that will hold the number of bytes used by the abbrevation in the DWARF ``.debug_abbrev'' section. Argument attr_count should point to a location that will hold the number of attributes in the abbrevation. If argument err is not NULL, it will be used to store error information in case of an error. Memory Management The memory area used for the Dwarf_Abbrev descriptor returned in argument ret_abbrev is allocated by the DWARF Access Library (libdwarf, -ldwarf). Application code should use function dwarf_dealloc() with the allocation type DW_DLA_ABBREV to free the memory area when the Dwarf_Abbrev descriptor is no longer needed. Application Programming Notes The last abbreviation entry in a standard DWARF abbreviation section will have a special length value of 1. RETURN VALUES
Function dwarf_get_abbrev() returns DW_DLV_OK when it succeeds. It returns DW_DLV_NO_ENTRY if there is no abbreviation information at offset offset. In case of an error, it returns DW_DLV_ERROR and sets the argument err. ERRORS
Function dwarf_get_abbrev() can fail with: [DW_DLE_ARGUMENT] One of the arguments dbg, ret_abbrev, length or attr_count was NULL. [DW_DLE_NO_ENTRY] There is no abbreviation information at offset offset. EXAMPLE
To loop through all the abbreviation information associated with a DWARF debug context, use: Dwarf_Debug dbg; Dwarf_Abbrev ab; Dwarf_Off aboff; Dwarf_Unsigned length, attr_count; Dwarf_Half tag; Dwarf_Error de; int ret; while ((ret = dwarf_next_cu_header(dbg, NULL, NULL, &aboff, NULL, NULL, &de)) == DW_DLV_OK) { while ((ret = dwarf_get_abbrev(re->dbg, aboff, &ab, &length, &attr_count, &de)) == DW_DLV_OK) { if (length == 1) /* Last entry. */ break; aboff += length; if (dwarf_get_abbrev_tag(ab, &tag, &de) != DW_DLV_OK) { warnx("dwarf_get_abbrev_tag failed: %s", dwarf_errmsg(de)); continue; } if (ret != DW_DLV_OK) warnx("dwarf_get_abbrev: %s", dwarf_errmsg(de)); } if (ret == DW_DLV_ERROR) warnx("dwarf_next_cu_header: %s", dwarf_errmsg(de)); SEE ALSO
dwarf(3), dwarf_dealloc(3), dwarf_get_abbrev_tag(3), dwarf_get_abbrev_code(3), dwarf_get_abbrev_children_flag(3), dwarf_get_abbrev_entry(3) BSD
March 27, 2011 BSD

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