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_loclist.3 3644 2018-10-15 19:55:01Z jkoshy $ 26.\" 27.Dd November 9, 2011 28.Dt DWARF_LOCLIST 3 29.Os 30.Sh NAME 31.Nm dwarf_loclist , 32.Nm dwarf_loclist_n 33.Nd retrieve DWARF location expression information 34.Sh LIBRARY 35.Lb libdwarf 36.Sh SYNOPSIS 37.In libdwarf.h 38.Ft int 39.Fo dwarf_loclist 40.Fa "Dwarf_Attribute at" 41.Fa "Dwarf_Locdesc **llbuf" 42.Fa "Dwarf_Signed *listlen" 43.Fa "Dwarf_Error *error" 44.Fc 45.Ft int 46.Fo dwarf_loclist_n 47.Fa "Dwarf_Attribute at" 48.Fa "Dwarf_Locdesc ***llbuf" 49.Fa "Dwarf_Signed *listlen" 50.Fa "Dwarf_Error *error" 51.Fc 52.Sh DESCRIPTION 53These functions retrieve the location expressions 54associated with a DWARF attribute. 55.Pp 56Note: function 57.Fn dwarf_loclist 58is deprecated. 59New application code should instead use function 60.Fn dwarf_loclist_n 61.Pp 62Function 63.Fn dwarf_loclist_n 64retrieves the list of location expressions associated with a DWARF 65attribute. 66Argument 67.Ar at 68should reference a valid DWARF attribute. 69Argument 70.Ar llbuf 71should point to a location which will hold a returned array of 72pointers to 73.Vt Dwarf_Locdesc 74descriptors. 75Argument 76.Ar listlen 77should point to a location which will be set to the number of 78elements contained in the returned array. 79If argument 80.Ar err 81is not NULL, it will be used to store error information in case 82of an error. 83.Pp 84Function 85.Fn dwarf_loclist 86retrieves the first location expression associated with an attribute. 87Argument 88.Ar at 89should reference a valid DWARF attribute. 90Argument 91.Ar llbuf 92should point to a location which will hold the returned pointer 93to a 94.Vt Dwarf_Locdesc 95descriptor. 96Argument 97.Ar listlen 98should point to a location which will be always set to 1. 99If argument 100.Ar err 101is not NULL, it will be used to store error information in case 102of an error. 103.Pp 104.Vt Dwarf_Locdesc 105descriptors are defined in the header file 106.In libdwarf.h , 107and consist of following fields: 108.Pp 109.Bl -tag -width ".Va ld_cents" -compact 110.It Va ld_lopc 111The lowest program counter address covered by the descriptor. 112This field will be set to 0 if the descriptor is not associated with 113an address range. 114.It Va ld_hipc 115The highest program counter address covered by the descriptor. 116This field will be set to 0 if the descriptor is not associated with 117an address range. 118.It Va ld_cents 119The number of entries returned in 120.Va ld_s 121field. 122.It Va ld_s 123Pointer to an array of 124.Vt Dwarf_Loc 125descriptors. 126.El 127.Pp 128Each 129.Vt Dwarf_Loc 130descriptor represents one operation of a location expression. 131These descriptors are defined in the header file 132.In libdwarf.h , 133and consist of following fields: 134.Pp 135.Bl -tag -width ".Va lr_number2" -compact 136.It Va lr_atom 137The operator name, one of the 138.Dv DW_OP_* 139constants defined in the header file 140.In dwarf.h . 141.It Va lr_number 142The first operand of this operation. 143.It Va lr_number2 144The second operand of this operation. 145.It Va lr_offset 146The byte offset of this operation within the containing location 147expression. 148.El 149.Ss Memory Management 150The memory area used for the descriptor array returned in argument 151.Ar llbuf 152is allocated by the 153.Lb libdwarf . 154When the descriptor array is no longer needed, application code should 155use function 156.Xr dwarf_dealloc 3 157to free the memory area in the following manner: 158.Bl -enum 159.It 160First, the 161.Ar ld_s 162field of each 163.Vt Dwarf_Locdesc 164descriptor should be deallocated using the allocation type 165.Dv DW_DLA_LOC_BLOCK . 166.It 167Then, the application should free each 168.Vt Dwarf_Locdesc 169descriptor using the allocation type 170.Dv DW_DLA_LOCDESC . 171.It 172Finally, the 173.Va llbuf 174pointer should be deallocated using the allocation type 175.Dv DW_DLA_LIST . 176.El 177.Sh RETURN VALUES 178On success, these functions returns 179.Dv DW_DLV_OK . 180In case of an error, they return 181.Dv DW_DLV_ERROR 182and set the argument 183.Ar err . 184.Sh EXAMPLES 185To retrieve the location list associated with an attribute, use: 186.Bd -literal -offset indent 187Dwarf_Attribute at; 188Dwarf_Locdesc **llbuf; 189Dwarf_Signed lcnt; 190Dwarf_Loc *lr; 191Dwarf_Error de; 192int i; 193 194if (dwarf_loclist_n(at, &llbuf, &lcnt, &de) != DW_DLV_OK) 195 errx(EXIT_FAILURE, "dwarf_loclist_n failed: %s", 196 dwarf_errmsg(de)); 197 198for (i = 0; i < lcnt; i++) { 199 /* ... Use llbuf[i] ... */ 200 for (j = 0; (Dwarf_Half) j < llbuf[i]->ld_cents; j++) { 201 lr = &llbuf[i]->ld_s[j]; 202 /* ... Use each Dwarf_Loc descriptor ... */ 203 } 204 dwarf_dealloc(dbg, llbuf[i]->ld_s, DW_DLA_LOC_BLOCK); 205 dwarf_dealloc(dbg, llbuf[i], DW_DLA_LOCDESC); 206} 207dwarf_dealloc(dbg, llbuf, DW_DLA_LIST); 208.Ed 209.Sh ERRORS 210These functions can fail with: 211.Bl -tag -width ".Bq Er DW_DLE_ARGUMENT" 212.It Bq Er DW_DLE_ARGUMENT 213One of the arguments 214.Ar at , 215.Ar llbuf 216or 217.Ar listlen 218was NULL. 219.It Bq Er DW_DLE_ARGUMENT 220The attribute provided by argument 221.Ar at 222does not contain a location expression or is not associated with a 223location expression list. 224.El 225.Sh SEE ALSO 226.Xr dwarf 3 , 227.Xr dwarf_dealloc 3 , 228.Xr dwarf_get_loclist_entry 3 , 229.Xr dwarf_loclist_from_expr 3 , 230.Xr dwarf_loclist_from_expr_a 3 231