1.\" Copyright (c) 2011 Kai Wang
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25.\" $Id: dwarf_add_expr_gen.3 2072 2011-10-27 03:26:49Z jkoshy $
26.\"
27.Dd September 9, 2011
28.Os
29.Dt DWARF_ADD_EXPR_GEN 3
30.Sh NAME
31.Nm dwarf_add_expr_gen
32.Nd add an operator to a location expression descriptor
33.Sh LIBRARY
34.Lb libdwarf
35.Sh SYNOPSIS
36.In libdwarf.h
37.Ft "Dwarf_Unsigned"
38.Fo dwarf_add_expr_gen
39.Fa "Dwarf_P_Expr expr"
40.Fa "Dwarf_Small opcode"
41.Fa "Dwarf_Unsigned val1"
42.Fa "Dwarf_Unsigned val2"
43.Fa "Dwarf_Error *err"
44.Fc
45.Sh DESCRIPTION
46Function
47.Fn dwarf_add_expr_gen
48adds a location expression operator to the location expression
49descriptor referenced by argument
50.Ar expr .
51.Pp
52Argument
53.Ar expr
54should reference a location expression descriptor allocated using
55the function
56.Xr dwarf_new_expr 3 .
57.Pp
58Argument
59.Ar opcode
60specifies the operation code of the location expression operator.
61Valid values for this argument are those denoted by the
62.Dv DW_OP_ Ns *
63constants defined in
64.In libdwarf.h .
65.Pp
66To generate a
67.Dv DW_OP_addr
68operation, application code should instead use
69.Xr dwarf_add_expr_addr_b 3 .
70.Pp
71Argument
72.Ar val1
73specifies the first operand of the location expression operator.
74.Pp
75Argument
76.Ar val2
77specifies the second operand of the location expression operator.
78.Pp
79If argument
80.Ar err
81is not NULL, it will be used to store error information in case
82of an error.
83.Sh RETURN VALUES
84On success, function
85.Fn dwarf_add_expr_gen
86returns the size in bytes of the location expression byte stream
87generated.
88In case of an error, function
89.Fn dwarf_add_expr_gen
90returns
91.Dv DW_DLV_NOCOUNT
92and sets the argument
93.Ar err .
94.Sh ERRORS
95Function
96.Fn dwarf_add_expr_gen
97can fail with:
98.Bl -tag -width ".Bq Er DW_DLE_LOC_EXPR_BAD"
99.It Bq Er DW_DLE_ARGUMENT
100Argument
101.Ar expr
102was NULL.
103.It Bq Er DW_DLE_LOC_EXPR_BAD
104The operation code specified in argument
105.Ar opcode
106was invalid.
107.It Bq Er DW_DLE_MEMORY
108An out of memory condition was encountered during the execution of
109the function.
110.El
111.Sh SEE ALSO
112.Xr dwarf 3 ,
113.Xr dwarf_add_AT_location_expr 3 ,
114.Xr dwarf_add_expr_addr 3 ,
115.Xr dwarf_add_expr_addr_b 3 ,
116.Xr dwarf_expr_current_offset 3 ,
117.Xr dwarf_expr_into_block 3 ,
118.Xr dwarf_new_expr 3
119