1.\" $NetBSD: dwarf_new_expr.3,v 1.4 2020/11/26 22:51:35 jkoshy Exp $ 2.\" 3.\" Copyright (c) 2011 Kai Wang 4.\" All rights reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 15.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 16.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 17.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 18.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 19.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 20.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 21.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 22.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 23.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 24.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 25.\" SUCH DAMAGE. 26.\" 27.\" Id: dwarf_new_expr.3 3644 2018-10-15 19:55:01Z jkoshy 28.\" 29.Dd September 8, 2011 30.Dt DWARF_NEW_EXPR 3 31.Os 32.Sh NAME 33.Nm dwarf_new_expr 34.Nd create a location expression descriptor 35.Sh LIBRARY 36.Lb libdwarf 37.Sh SYNOPSIS 38.In libdwarf.h 39.Ft "Dwarf_P_Expr" 40.Fo dwarf_new_expr 41.Fa "Dwarf_P_Debug dbg" 42.Fa "Dwarf_Error *err" 43.Fc 44.Sh DESCRIPTION 45Function 46.Fn dwarf_new_expr 47allocates a DWARF location expression descriptor used to build up a 48location expression stream. 49.Pp 50The application can use the functions 51.Xr dwarf_add_expr_gen 3 52and 53.Xr dwarf_add_expr_addr_b 3 54to add location expression operators to the created descriptor. 55When done, the application can call the function 56.Xr dwarf_expr_into_block 3 57to retrieve the generated byte stream for the location expression, 58or call the function 59.Xr dwarf_add_AT_location_expr 3 60to create an attribute with the location expression stream as its 61value. 62.Pp 63Argument 64.Ar dbg 65should reference a DWARF producer instance allocated using 66.Xr dwarf_producer_init 3 67or 68.Xr dwarf_producer_init_b 3 . 69.Pp 70If argument 71.Ar err 72is not NULL, it will be used to store error information in case 73of an error. 74.Sh RETURN VALUES 75On success, function 76.Fn dwarf_new_expr 77returns the created location expression descriptor. 78In case of an error, function 79.Fn dwarf_new_expr 80returns 81.Dv DW_DLV_BADADDR 82and sets the argument 83.Ar err . 84.Sh EXAMPLES 85To create a location expression descriptor, add location expression 86operators to it and to retrieve the generated byte stream, 87use: 88.Bd -literal -offset indent 89Dwarf_P_Debug dbg; 90Dwarf_Error de; 91Dwarf_P_Expr pe; 92Dwarf_Addr buf; 93Dwarf_Unsigned len; 94 95/* ...Assume that `dbg' refers to a DWARF producer instance... */ 96 97if ((pe = dwarf_new_expr(dbg, &de)) == DW_DLV_BADADDR) { 98 warnx("dwarf_new_expr failed: %s", dwarf_errmsg(-1)); 99 return; 100} 101 102if (dwarf_add_expr_gen(pe, DW_OP_regx, 55, 0, &de) == 103 DW_DLV_NOCOUNT) { 104 warnx("dwarf_add_expr_gen failed: %s", dwarf_errmsg(-1)); 105 return; 106} 107 108if ((buf = dwarf_expr_into_block(pe, &len, &de)) == 109 DW_DLV_BADADDR) { 110 warnx("dwarf_expr_into_block failed: %s", 111 dwarf_errmsg(-1)); 112 return; 113} 114.Ed 115.Sh ERRORS 116Function 117.Fn dwarf_new_expr 118can fail with: 119.Bl -tag -width ".Bq Er DW_DLE_ARGUMENT" 120.It Bq Er DW_DLE_ARGUMENT 121Argument 122.Ar dbg 123was NULL. 124.It Bq Er DW_DLE_MEMORY 125An out of memory condition was encountered during the execution of 126the function. 127.El 128.Sh SEE ALSO 129.Xr dwarf 3 , 130.Xr dwarf_add_AT_location_expr 3 , 131.Xr dwarf_add_expr_addr 3 , 132.Xr dwarf_add_expr_addr_b 3 , 133.Xr dwarf_add_expr_gen 3 , 134.Xr dwarf_expr_current_offset 3 , 135.Xr dwarf_expr_into_block 3 , 136.Xr dwarf_producer_init 3 , 137.Xr dwarf_producer_init_b 3 138