1.\" Copyright (c) 2010 Joseph Koshy
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25.\" $Id: dwarf_formref.3 3640 2018-10-14 14:09:13Z jkoshy $
26.\"
27.Dd June 21, 2010
28.Dt DWARF_FORMREF 3
29.Os
30.Sh NAME
31.Nm dwarf_formref ,
32.Nm dwarf_global_formref
33.Nd retrieve offsets for REFERENCE class attributes
34.Sh LIBRARY
35.Lb libdwarf
36.Sh SYNOPSIS
37.In libdwarf.h
38.Ft int
39.Fo dwarf_formref
40.Fa "Dwarf_Attribute attr"
41.Fa "Dwarf_Off *retoffset"
42.Fa "Dwarf_Error *err"
43.Fc
44.Ft int
45.Fo dwarf_global_formref
46.Fa "Dwarf_Attribute attr"
47.Fa "Dwarf_Off *retoffset"
48.Fa "Dwarf_Error *err"
49.Fc
50.Sh DESCRIPTION
51These functions return the offsets associated with a DWARF attribute
52descriptor.
53.Pp
54Function
55.Fn dwarf_formref
56returns the compilation unit relative offset of the descriptor
57referenced by argument
58.Ar attr
59in the location pointed to by argument
60.Ar retoffset .
61Argument
62.Ar attr
63must be a reference that is local to a compilation unit.
64Permitted forms for argument
65.Ar attr
66are
67.Dv DW_FORM_ref1 ,
68.Dv DW_FORM_ref2 ,
69.Dv DW_FORM_ref4 ,
70.Dv DW_FORM_ref8
71and
72.Dv DW_FORM_ref_udata .
73.Pp
74Function
75.Fn dwarf_global_formref
76returns the section-relative offset of the descriptor referenced by
77argument
78.Ar attr
79in the location pointed to by argument
80.Ar retoffset .
81Argument
82.Ar attr
83should be a legal
84.Sy REFERENCE
85class form.
86Permitted forms for argument
87.Ar attr
88are:
89.Dv DW_FORM_ref_addr ,
90.Dv DW_FORM_ref_udata ,
91.Dv DW_FORM_ref1 ,
92.Dv DW_FORM_ref2 ,
93.Dv DW_FORM_ref4 ,
94.Dv DW_FORM_ref8
95and
96.Dv DW_FORM_sec_offset .
97The returned offset is relative to the start of the
98.Dq .debug_info
99ELF section.
100.Pp
101If argument
102.Ar err
103is not NULL, it will be used to return an error descriptor in case
104of an error.
105.Sh RETURN VALUES
106These functions return
107.Dv DW_DLV_OK
108on success.
109In case of an error, these functions return
110.Dv DW_DLV_ERROR
111and sets argument
112.Ar err .
113.Sh ERRORS
114These functions may fail with the following errors:
115.Bl -tag -width ".Bq Er DW_DLE_ATTR_FORM_BAD"
116.It Bq Er DW_DLE_ARGUMENT
117Either of arguments
118.Ar attr
119or
120.Ar retoffset
121was NULL.
122.It Bq Er DW_DLE_ATTR_FORM_BAD
123The attribute referenced by argument
124.Ar attr
125was not of a permitted kind.
126.El
127.Sh SEE ALSO
128.Xr dwarf 3 ,
129.Xr dwarf_attr 3 ,
130.Xr dwarf_formblock 3 ,
131.Xr dwarf_formflag 3 ,
132.Xr dwarf_formsdata 3 ,
133.Xr dwarf_formsig8 3 ,
134.Xr dwarf_formstring 3 ,
135.Xr dwarf_formudata 3 ,
136.Xr dwarf_hasattr 3
137