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”. Abbreviation 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.

EXAMPLES

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));

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.