1.\" Copyright (c) 2011 Kai Wang 2.\" All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 13.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 14.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 15.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 16.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 17.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 18.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 19.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 20.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 21.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 22.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 23.\" SUCH DAMAGE. 24.\" 25.\" $Id: dwarf_new_expr.3 3644 2018-10-15 19:55:01Z jkoshy $ 26.\" 27.Dd September 8, 2011 28.Dt DWARF_NEW_EXPR 3 29.Os 30.Sh NAME 31.Nm dwarf_new_expr 32.Nd create a location expression descriptor 33.Sh LIBRARY 34.Lb libdwarf 35.Sh SYNOPSIS 36.In libdwarf.h 37.Ft "Dwarf_P_Expr" 38.Fo dwarf_new_expr 39.Fa "Dwarf_P_Debug dbg" 40.Fa "Dwarf_Error *err" 41.Fc 42.Sh DESCRIPTION 43Function 44.Fn dwarf_new_expr 45allocates a DWARF location expression descriptor used to build up a 46location expression stream. 47.Pp 48The application can use the functions 49.Xr dwarf_add_expr_gen 3 50and 51.Xr dwarf_add_expr_addr_b 3 52to add location expression operators to the created descriptor. 53When done, the application can call the function 54.Xr dwarf_expr_into_block 3 55to retrieve the generated byte stream for the location expression, 56or call the function 57.Xr dwarf_add_AT_location_expr 3 58to create an attribute with the location expression stream as its 59value. 60.Pp 61Argument 62.Ar dbg 63should reference a DWARF producer instance allocated using 64.Xr dwarf_producer_init 3 65or 66.Xr dwarf_producer_init_b 3 . 67.Pp 68If argument 69.Ar err 70is not NULL, it will be used to store error information in case 71of an error. 72.Sh RETURN VALUES 73On success, function 74.Fn dwarf_new_expr 75returns the created location expression descriptor. 76In case of an error, function 77.Fn dwarf_new_expr 78returns 79.Dv DW_DLV_BADADDR 80and sets the argument 81.Ar err . 82.Sh EXAMPLES 83To create a location expression descriptor, add location expression 84operators to it and to retrieve the generated byte stream, 85use: 86.Bd -literal -offset indent 87Dwarf_P_Debug dbg; 88Dwarf_Error de; 89Dwarf_P_Expr pe; 90Dwarf_Addr buf; 91Dwarf_Unsigned len; 92 93/* ...Assume that `dbg' refers to a DWARF producer instance... */ 94 95if ((pe = dwarf_new_expr(dbg, &de)) == DW_DLV_BADADDR) { 96 warnx("dwarf_new_expr failed: %s", dwarf_errmsg(-1)); 97 return; 98} 99 100if (dwarf_add_expr_gen(pe, DW_OP_regx, 55, 0, &de) == 101 DW_DLV_NOCOUNT) { 102 warnx("dwarf_add_expr_gen failed: %s", dwarf_errmsg(-1)); 103 return; 104} 105 106if ((buf = dwarf_expr_into_block(pe, &len, &de)) == 107 DW_DLV_BADADDR) { 108 warnx("dwarf_expr_into_block failed: %s", 109 dwarf_errmsg(-1)); 110 return; 111} 112.Ed 113.Sh ERRORS 114Function 115.Fn dwarf_new_expr 116can fail with: 117.Bl -tag -width ".Bq Er DW_DLE_ARGUMENT" 118.It Bq Er DW_DLE_ARGUMENT 119Argument 120.Ar dbg 121was NULL. 122.It Bq Er DW_DLE_MEMORY 123An out of memory condition was encountered during the execution of 124the function. 125.El 126.Sh SEE ALSO 127.Xr dwarf 3 , 128.Xr dwarf_add_AT_location_expr 3 , 129.Xr dwarf_add_expr_addr 3 , 130.Xr dwarf_add_expr_addr_b 3 , 131.Xr dwarf_add_expr_gen 3 , 132.Xr dwarf_expr_current_offset 3 , 133.Xr dwarf_expr_into_block 3 , 134.Xr dwarf_producer_init 3 , 135.Xr dwarf_producer_init_b 3 136