1 | .\" Copyright (c) 2011 Kai Wang |
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2 | .\" All rights reserved. |
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3 | .\" |
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5 | .\" modification, are permitted provided that the following conditions |
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13 | .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND |
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14 | .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE |
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25 | .\" $Id: dwarf_new_expr.3 2074 2011-10-27 03:34:33Z jkoshy $ |
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26 | .\" |
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27 | .Dd September 8, 2011 |
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28 | .Os |
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29 | .Dt DWARF_NEW_EXPR 3 |
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30 | .Sh NAME |
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31 | .Nm dwarf_new_expr |
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32 | .Nd create a location expression descriptor |
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33 | .Sh LIBRARY |
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34 | .Lb libdwarf |
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35 | .Sh SYNOPSIS |
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36 | .In libdwarf.h |
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37 | .Ft "Dwarf_P_Expr" |
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38 | .Fo dwarf_new_expr |
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39 | .Fa "Dwarf_P_Debug dbg" |
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40 | .Fa "Dwarf_Error *err" |
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41 | .Fc |
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42 | .Sh DESCRIPTION |
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43 | Function |
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44 | .Fn dwarf_new_expr |
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45 | allocates a DWARF location expression descriptor used to build up a |
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46 | location expression stream. |
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47 | .Pp |
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48 | The application can use the functions |
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49 | .Xr dwarf_add_expr_gen 3 |
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50 | and |
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51 | .Xr dwarf_add_expr_addr_b 3 |
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52 | to add location expression operators to the created descriptor. |
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53 | When done, the application can call the function |
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54 | .Xr dwarf_expr_into_block 3 |
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55 | to retrieve the generated byte stream for the location expression, |
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56 | or call the function |
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57 | .Xr dwarf_add_AT_location_expr 3 |
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58 | to create an attribute with the location expression stream as its |
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59 | value. |
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60 | .Pp |
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61 | Argument |
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62 | .Ar dbg |
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63 | should reference a DWARF producer instance allocated using |
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64 | .Xr dwarf_producer_init 3 |
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65 | or |
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66 | .Xr dwarf_producer_init_b 3 . |
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67 | .Pp |
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68 | If argument |
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69 | .Ar err |
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70 | is not NULL, it will be used to store error information in case |
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71 | of an error. |
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72 | .Sh RETURN VALUES |
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73 | On success, function |
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74 | .Fn dwarf_new_expr |
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75 | returns the created location expression descriptor. |
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76 | In case of an error, function |
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77 | .Fn dwarf_new_expr |
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78 | returns |
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79 | .Dv DW_DLV_BADADDR |
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80 | and sets the argument |
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81 | .Ar err . |
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82 | .Sh ERRORS |
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83 | Function |
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84 | .Fn dwarf_new_expr |
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85 | can fail with: |
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86 | .Bl -tag -width ".Bq Er DW_DLE_ARGUMENT" |
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87 | .It Bq Er DW_DLE_ARGUMENT |
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88 | Argument |
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89 | .Ar dbg |
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90 | was NULL. |
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91 | .It Bq Er DW_DLE_MEMORY |
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92 | An out of memory condition was encountered during the execution of |
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93 | the function. |
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94 | .El |
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95 | .Sh EXAMPLES |
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96 | To create a location expression descriptor, add location expression |
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97 | operators to it and to retrieve the generated byte stream, |
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98 | use: |
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99 | .Bd -literal -offset indent |
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100 | Dwarf_P_Debug dbg; |
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101 | Dwarf_Error de; |
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102 | Dwarf_P_Expr pe; |
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103 | Dwarf_Addr buf; |
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104 | Dwarf_Unsigned len; |
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105 | |
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106 | /* ...Assume that `dbg' refers to a DWARF producer instance... */ |
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107 | |
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108 | if ((pe = dwarf_new_expr(dbg, &de)) == DW_DLV_BADADDR) { |
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109 | warnx("dwarf_new_expr failed: %s", dwarf_errmsg(-1)); |
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110 | return; |
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111 | } |
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112 | |
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113 | if (dwarf_add_expr_gen(pe, DW_OP_regx, 55, 0, &de) == |
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114 | DW_DLV_NOCOUNT) { |
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115 | warnx("dwarf_add_expr_gen failed: %s", dwarf_errmsg(-1)); |
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116 | return; |
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117 | } |
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118 | |
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119 | if ((buf = dwarf_expr_into_block(pe, &len, &de)) == |
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120 | DW_DLV_BADADDR) { |
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121 | warnx("dwarf_expr_into_block failed: %s", |
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122 | dwarf_errmsg(-1)); |
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123 | return; |
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124 | } |
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125 | .Ed |
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126 | .Sh SEE ALSO |
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127 | .Xr dwarf 3 , |
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128 | .Xr dwarf_add_AT_location_expr 3 , |
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129 | .Xr dwarf_add_expr_gen 3 , |
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130 | .Xr dwarf_add_expr_addr 3 , |
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131 | .Xr dwarf_add_expr_addr_b 3 , |
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132 | .Xr dwarf_expr_current_offset 3 , |
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133 | .Xr dwarf_expr_into_block 3 , |
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134 | .Xr dwarf_producer_init 3 , |
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135 | .Xr dwarf_producer_init_b 3 |
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