xref: /freebsd/contrib/elftoolchain/libdwarf/dwarf_get_abbrev_entry.3 (revision ae500c1ff8974130f7f2692772cf288b90349e0d)

.\" Copyright (c) 2011 Kai Wang
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.\" $Id: dwarf_get_abbrev_entry.3 3644 2018-10-15 19:55:01Z jkoshy $
.\"
.Dd April 02, 2011
.Dt DWARF_GET_ABBREV_ENTRY 3
.Os
.Sh NAME
.Nm dwarf_get_abbrev_entry
.Nd retrieve attribute information from an abbreviation descriptor
.Sh LIBRARY
.Lb libdwarf
.Sh SYNOPSIS
.In libdwarf.h
.Ft int
.Fo dwarf_get_abbrev_entry
.Fa "Dwarf_Abbrev abbrev"
.Fa "Dwarf_Signed ndx"
.Fa "Dwarf_Half *code"
.Fa "Dwarf_Signed *form"
.Fa "Dwarf_Off *offset"
.Fa "Dwarf_Error *err"
.Fc
.Sh DESCRIPTION
Function
.Fn dwarf_get_abbrev_entry
retrieves attribute information from a DWARF abbreviation descriptor.
.Pp
Argument
.Ar abbrev
should be a valid abbreviation descriptor, as returned by function
.Xr dwarf_get_abbrev 3 .
.Pp
Argument
.Ar ndx
specifies the 0-based index of the attribute.
The total count of the attributes contained in the abbreviation
entry can be retrieved using the function
.Xr dwarf_get_abbrev 3 .
.Pp
Argument
.Ar code
should point to a location which will hold a returned
attribute code.
.Pp
Argument
.Ar form
should point to a location which will hold the returned
form of the attribute.
.Pp
Argument
.Ar offset
should point to a location which will hold a returned offset, relative
to the
.Dq ".debug_abbrev"
section, for the specified attribute.
.Pp
If argument
.Ar err
is not NULL, it will be used to return an error descriptor in case
of an error.
.Sh RETURN VALUES
Function
.Fn dwarf_get_abbrev_entry
returns
.Dv DW_DLV_OK
when it succeeds.
It returns
.Dv DW_DLV_NO_ENTRY
if the attribute index specified by argument
.Ar ndx
is out of range.
In case of an error, it returns
.Dv DW_DLV_ERROR
and sets the argument
.Ar err .
.Sh EXAMPLES
To loop through all the attribute entries contained in the
abbreviation section, use:
.Bd -literal -offset indent
Dwarf_Debug dbg;
Dwarf_Abbrev ab;
Dwarf_Off aboff, atoff;
Dwarf_Signed form;
Dwarf_Half attr;
Dwarf_Unsigned length, attr_count;
Dwarf_Error de;
int i, ret;

/* ...allocate 'dbg' using dwarf_init(3) ... */

while ((ret = dwarf_next_cu_header(dbg, NULL, NULL, &aboff,
    NULL, NULL, &de)) ==  DW_DLV_OK) {
	while ((ret = dwarf_get_abbrev(dbg, aboff, &ab, &length,
	    &attr_count, &de)) == DW_DLV_OK) {
		if (length == 1)	/* Last entry. */
			break;
		aboff += length;
		for (i = 0; (Dwarf_Unsigned) i < attr_count; i++) {
			if (dwarf_get_abbrev_entry(ab, i,
			    &attr, &form, &atoff, &de) != DW_DLV_OK) {
				warnx("dwarf_get_abbrev_entry failed:"
				    " %s", dwarf_errmsg(de));
				continue;
			}
			/* .. use the retrieved information ... */
		}
	}

	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));
.Ed
.Sh ERRORS
Function
.Fn dwarf_get_abbrev_entry
can fail with:
.Bl -tag -width ".Bq Er DW_DLE_NO_ENTRY"
.It Bq Er DW_DLE_ARGUMENT
One of the arguments
.Ar abbrev ,
.Ar code ,
.Ar form
or
.Ar offset
was NULL.
.It Bq Er DW_DLE_NO_ENTRY
The attribute index specified by argument
.Ar ndx
was out of range.
.El
.Sh SEE ALSO
.Xr dwarf 3 ,
.Xr dwarf_get_abbrev 3