1.\" Copyright (c) 2011 Kai Wang
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25.\" $Id: dwarf_get_abbrev_entry.3 2071 2011-10-27 03:20:00Z jkoshy $
26.\"
27.Dd April 02, 2011
28.Os
29.Dt DWARF_GET_ABBREV_ENTRY 3
30.Sh NAME
31.Nm dwarf_get_abbrev_entry
32.Nd retrieve attribute information from an abbreviation descriptor
33.Sh LIBRARY
34.Lb libdwarf
35.Sh SYNOPSIS
36.In libdwarf.h
37.Ft int
38.Fo dwarf_get_abbrev_entry
39.Fa "Dwarf_Abbrev abbrev"
40.Fa "Dwarf_Signed ndx"
41.Fa "Dwarf_Half *code"
42.Fa "Dwarf_Signed *form"
43.Fa "Dwarf_Off *offset"
44.Fa "Dwarf_Error *err"
45.Fc
46.Sh DESCRIPTION
47Function
48.Fn dwarf_get_abbrev_entry
49retrieves attribute information from a DWARF abbreviation descriptor.
50.Pp
51Argument
52.Ar abbrev
53should be a valid abbreviation descriptor, as returned by function
54.Xr dwarf_get_abbrev 3 .
55.Pp
56Argument
57.Ar ndx
58specifies the 0-based index of the attribute.
59The total count of the attributes contained in the abbreviation
60entry can be retrieved using the function
61.Xr dwarf_get_abbrev 3 .
62.Pp
63Argument
64.Ar code
65should point to a location which will hold a returned
66attribute code.
67.Pp
68Argument
69.Ar form
70should point to a location which will hold the returned
71form of the attribute.
72.Pp
73Argument
74.Ar offset
75should point to a location which will hold a returned offset, relative
76to the
77.Dq ".debug_abbrev"
78section, for the specified attribute.
79.Pp
80If argument
81.Ar err
82is not NULL, it will be used to return an error descriptor in case
83of an error.
84.Sh RETURN VALUES
85Function
86.Fn dwarf_get_abbrev_entry
87returns
88.Dv DW_DLV_OK
89when it succeeds.
90It returns
91.Dv DW_DLV_NO_ENTRY
92if the attribute index specified by argument
93.Ar ndx
94is out of range.
95In case of an error, it returns
96.Dv DW_DLV_ERROR
97and sets the argument
98.Ar err .
99.Sh ERRORS
100Function
101.Fn dwarf_get_abbrev_entry
102can fail with:
103.Bl -tag -width ".Bq Er DW_DLE_NO_ENTRY"
104.It Bq Er DW_DLE_ARGUMENT
105One of the arguments
106.Ar abbrev ,
107.Ar code ,
108.Ar form
109or
110.Ar offset
111was NULL.
112.It Bq Er DW_DLE_NO_ENTRY
113The attribute index specified by argument
114.Ar ndx
115was out of range.
116.El
117.Sh EXAMPLE
118To loop through all the attribute entries contained in the
119abbreviation section, use:
120.Bd -literal -offset indent
121Dwarf_Debug dbg;
122Dwarf_Abbrev ab;
123Dwarf_Off aboff, atoff;
124Dwarf_Signed form;
125Dwarf_Half attr;
126Dwarf_Unsigned length, attr_count;
127Dwarf_Error de;
128int i, ret;
129
130/* ...allocate 'dbg' using dwarf_init(3) ... */
131
132while ((ret = dwarf_next_cu_header(dbg, NULL, NULL, &aboff,
133    NULL, NULL, &de)) ==  DW_DLV_OK) {
134	while ((ret = dwarf_get_abbrev(dbg, aboff, &ab, &length,
135	    &attr_count, &de)) == DW_DLV_OK) {
136		if (length == 1)	/* Last entry. */
137			break;
138		aboff += length;
139		for (i = 0; (Dwarf_Unsigned) i < attr_count; i++) {
140			if (dwarf_get_abbrev_entry(ab, i,
141			    &attr, &form, &atoff, &de) != DW_DLV_OK) {
142				warnx("dwarf_get_abbrev_entry failed:"
143				    " %s", dwarf_errmsg(de));
144				continue;
145			}
146			/* .. use the retrieved information ... */
147		}
148	}
149
150	if (ret != DW_DLV_OK)
151		warnx("dwarf_get_abbrev: %s", dwarf_errmsg(de));
152}
153
154if (ret == DW_DLV_ERROR)
155	warnx("dwarf_next_cu_header: %s", dwarf_errmsg(de));
156.Ed
157.Sh SEE ALSO
158.Xr dwarf 3 ,
159.Xr dwarf_get_abbrev 3
160