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111
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1 -- C3A2002.A
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2 --
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3 -- Grant of Unlimited Rights
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4 --
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5 -- Under contracts F33600-87-D-0337, F33600-84-D-0280, MDA903-79-C-0687,
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6 -- F08630-91-C-0015, and DCA100-97-D-0025, the U.S. Government obtained
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7 -- unlimited rights in the software and documentation contained herein.
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8 -- Unlimited rights are defined in DFAR 252.227-7013(a)(19). By making
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9 -- this public release, the Government intends to confer upon all
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10 -- recipients unlimited rights equal to those held by the Government.
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11 -- These rights include rights to use, duplicate, release or disclose the
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12 -- released technical data and computer software in whole or in part, in
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13 -- any manner and for any purpose whatsoever, and to have or permit others
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14 -- to do so.
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15 --
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16 -- DISCLAIMER
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17 --
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18 -- ALL MATERIALS OR INFORMATION HEREIN RELEASED, MADE AVAILABLE OR
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19 -- DISCLOSED ARE AS IS. THE GOVERNMENT MAKES NO EXPRESS OR IMPLIED
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20 -- WARRANTY AS TO ANY MATTER WHATSOEVER, INCLUDING THE CONDITIONS OF THE
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21 -- SOFTWARE, DOCUMENTATION OR OTHER INFORMATION RELEASED, MADE AVAILABLE
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22 -- OR DISCLOSED, OR THE OWNERSHIP, MERCHANTABILITY, OR FITNESS FOR A
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23 -- PARTICULAR PURPOSE OF SAID MATERIAL.
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24 --*
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25 --
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26 -- OBJECTIVE:
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27 -- Check that, for X'Access of a general access type A, Program_Error is
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28 -- raised if the accessibility level of X is deeper than that of A.
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29 -- Check for the case where X denotes a view that is a dereference of an
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30 -- access parameter, or a rename thereof.
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31 --
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32 -- Check for cases where the actual corresponding to X is:
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33 -- (a) An allocator.
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34 -- (b) An expression of a named access type.
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35 -- (c) Obj'Access.
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36 --
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37 -- TEST DESCRIPTION:
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38 -- In order to satisfy accessibility requirements, the designated
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39 -- object X must be at the same or a less deep nesting level than the
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40 -- general access type A -- X must "live" as long as A. Nesting
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41 -- levels are the run-time nestings of masters: block statements;
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42 -- subprogram, task, and entry bodies; and accept statements. Packages
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43 -- are invisible to accessibility rules.
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44 --
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45 -- This test declares subprograms with access parameters, within which
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46 -- 'Access is attempted on a dereference of the access parameter, and
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47 -- assigned to an access object whose type A is declared at some nesting
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48 -- level. The test verifies that Program_Error is raised if the actual
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49 -- corresponding to the access parameter is:
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50 --
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51 -- (1) an allocator, and the accessibility level of the execution
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52 -- of the called subprogram is deeper than that of the access
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53 -- type A.
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54 --
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55 -- (2) an expression of a named access type, and the accessibility
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56 -- level of the named access type is deeper than that of the
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57 -- access type A.
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58 --
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59 -- (3) a reference to the Access attribute (e.g., X'Access), and
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60 -- the accessibility level of X is deeper than that of the
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61 -- access type A.
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62 --
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63 -- Note that the static nesting level of the actual corresponding to the
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64 -- access parameter can be deeper than that of the type A -- it is
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65 -- the run-time nesting that matters for accessibility rules. Consider
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66 -- the case where the access type A is declared within the called
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67 -- subprogram. The accessibility check will never fail, even if the
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68 -- actual happens to have a deeper static nesting level:
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69 --
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70 -- procedure P (X: access T) is
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71 -- type A is access all T; -- Static level = 2, e.g.
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72 -- Acc : A := X.all'Access; -- Check should never fail.
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73 -- begin null; end;
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74 -- . . .
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75 -- declare
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76 -- Actual : aliased T; -- Static level = 3, e.g.
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77 -- begin
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78 -- P (Actual'Access);
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79 -- end;
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80 --
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81 -- For the execution of P, the accessibility level of type A will
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82 -- always be deeper than that of Actual, so there is no danger of a
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83 -- dangling reference arising from the assignment to Acc. Thus,
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84 -- X.all'Access is safe, even though the static nesting level of
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85 -- Actual is deeper than that of A.
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86 --
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87 --
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88 -- CHANGE HISTORY:
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89 -- 06 Dec 94 SAIC ACVC 2.0
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90 --
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91 --!
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92
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93 package C3A2002_0 is
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94
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95 type Desig is array (1 .. 10) of Integer;
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96
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97 X0 : aliased Desig; -- Level = 0.
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98
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99 type Acc_L0 is access all Desig; -- Level = 0.
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100 A0 : Acc_L0;
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101
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102 type Result_Kind is (OK, P_E, O_E);
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103
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104 procedure A_Is_Level_0 (X: access Desig; R : out Result_Kind);
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105 procedure Never_Fails (X: access Desig; R : out Result_Kind);
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106
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107 end C3A2002_0;
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108
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109
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110 --==================================================================--
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111
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112 package body C3A2002_0 is
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113
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114 procedure A_Is_Level_0 (X : access Desig;
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115 R : out Result_Kind) is
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116 begin
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117 -- The accessibility level of the type of A0 is 0.
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118 A0 := X.all'Access;
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119 R := OK;
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120 exception
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121 when Program_Error =>
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122 R := P_E;
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123 when others =>
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124 R := O_E;
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125 end A_Is_Level_0;
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126
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127 -----------------------------------------------
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128 procedure Never_Fails (X: access Desig;
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129 R : out Result_Kind) is
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130 type Acc_Local is access all Desig;
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131 AL : Acc_Local;
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132 begin
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133 -- X.all'Access below will always be safe, since the accessibility
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134 -- level (although not necessarily the static nesting depth) of the
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135 -- type of AL will always be deeper than or the same as that of the
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136 -- actual corresponding to Y.
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137 AL := X.all'Access;
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138 R := OK;
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139 exception
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140 when Program_Error =>
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141 R := P_E;
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142 when others =>
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143 R := O_E;
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144 end Never_Fails;
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145
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146 end C3A2002_0;
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147
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148
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149 --==================================================================--
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150
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151
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152 with C3A2002_0;
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153 with Report;
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154
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155 procedure C3A2002 is
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156
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157 X1 : aliased C3A2002_0.Desig; -- Level = 1.
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158
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159 type Acc_L1 is access all C3A2002_0.Desig; -- Level = 1.
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160 A1 : Acc_L1;
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161
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162 Expr_L0 : C3A2002_0.Acc_L0 := C3A2002_0.X0'Access;
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163 Expr_L1 : Acc_L1 := X1'Access;
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164
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165 Res : C3A2002_0.Result_Kind;
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166
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167 use type C3A2002_0.Result_Kind;
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168
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169 -----------------------------------------------
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170 procedure A_Is_Level_1 (X : access C3A2002_0.Desig;
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171 R : out C3A2002_0.Result_Kind) is
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172 -- Dereference of an access_to_object value is aliased.
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173 Ren : C3A2002_0.Desig renames X.all; -- Renaming of a dereference
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174 begin -- of an access parameter.
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175 -- The accessibility level of the type of A1 is 1.
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176 A1 := Ren'Access;
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177 R := C3A2002_0.OK;
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178 exception
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179 when Program_Error =>
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180 R := C3A2002_0.P_E;
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181 when others =>
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182 R := C3A2002_0.O_E;
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183 end A_Is_Level_1;
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184
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185 -----------------------------------------------
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186 procedure Display_Results (Result : in C3A2002_0.Result_Kind;
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187 Expected: in C3A2002_0.Result_Kind;
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188 Message : in String) is
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189 begin
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190 if Result /= Expected then
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191 case Result is
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192 when C3A2002_0.OK => Report.Failed ("No exception raised: " &
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193 Message);
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194 when C3A2002_0.P_E => Report.Failed ("Program_Error raised: " &
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195 Message);
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196 when C3A2002_0.O_E => Report.Failed ("Unexpected exception " &
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197 "raised: " & Message);
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198 end case;
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199 end if;
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200 end Display_Results;
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201
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202 begin -- C3A2002
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203
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204 Report.Test ("C3A2002", "Check that, for X'Access of general access " &
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205 "type A, Program_Error is raised if the accessibility " &
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206 "level of X is deeper than that of A: X is an access " &
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207 "parameter; corresponding actual is an allocator, " &
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208 "expression of a named access type, Obj'Access, or a " &
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209 "rename thereof");
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210
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211
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212 -- Actual is X'Access:
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213
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214 C3A2002_0.Never_Fails (C3A2002_0.X0'Access, Res);
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215 Display_Results (Res, C3A2002_0.OK, "X0'Access, local access type");
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216
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217 C3A2002_0.A_Is_Level_0 (C3A2002_0.X0'Access, Res);
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218 Display_Results (Res, C3A2002_0.OK, "X0'Access, level 0 access type");
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219
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220 C3A2002_0.A_Is_Level_0 (X1'Access, Res);
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221 Display_Results (Res, C3A2002_0.P_E, "X1'Access, level 0 access type");
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222
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223 A_Is_Level_1 (X1'Access, Res);
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224 Display_Results (Res, C3A2002_0.OK, "X1'Access, level 1 access type");
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225
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226
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227 -- Actual is expression of a named access type:
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228
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229 C3A2002_0.Never_Fails (Expr_L1, Res);
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230 Display_Results (Res, C3A2002_0.OK, "Expr_L1, local access type");
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231
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232 C3A2002_0.A_Is_Level_0 (Expr_L1, Res);
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233 Display_Results (Res, C3A2002_0.P_E, "Expr_L1, level 0 access type");
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234
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235 A_Is_Level_1 (Expr_L0, Res);
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236 Display_Results (Res, C3A2002_0.OK, "Expr_L0, level 1 access type");
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237
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238 A_Is_Level_1 (Expr_L1, Res);
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239 Display_Results (Res, C3A2002_0.OK, "Expr_L1, level 1 access type");
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240
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241 -- Actual is allocator (level of execution = 2):
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242
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243 C3A2002_0.Never_Fails (new C3A2002_0.Desig, Res);
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244 Display_Results (Res, C3A2002_0.OK, "Allocator level 2, " &
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245 "local access type");
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246
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247 -- Since actual is an allocator, its accessibility level is that of
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248 -- the execution of the called subprogram, i.e., level 2.
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249
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250 C3A2002_0.A_Is_Level_0 (new C3A2002_0.Desig, Res);
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251 Display_Results (Res, C3A2002_0.P_E, "Allocator level 2, " &
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252 "level 0 access type");
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253
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254 A_Is_Level_1 (new C3A2002_0.Desig, Res);
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255 Display_Results (Res, C3A2002_0.P_E, "Allocator level 2, " &
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256 "level 1 access type");
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257
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258
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259 Block_L2:
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260 declare
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261 X2 : aliased C3A2002_0.Desig; -- Level = 2.
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262 type Acc_L2 is access all C3A2002_0.Desig; -- Level = 2.
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263 Expr_L2 : Acc_L2 := X1'Access;
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264 begin
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265
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266 -- Actual is X'Access:
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267
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268 C3A2002_0.Never_Fails (X2'Access, Res);
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269 Display_Results (Res, C3A2002_0.OK, "X2'Access, local access type");
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270
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271 C3A2002_0.A_Is_Level_0 (X2'Access, Res);
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272 Display_Results (Res, C3A2002_0.P_E, "X2'Access, level 0 access type");
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273
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274
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275 -- Actual is expression of a named access type:
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276
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277 A_Is_Level_1 (Expr_L2, Res);
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278 Display_Results (Res, C3A2002_0.P_E, "Expr_L2, level 1 access type");
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279
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280
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281 -- Actual is allocator (level of execution = 3):
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282
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283 C3A2002_0.Never_Fails (new C3A2002_0.Desig, Res);
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284 Display_Results (Res, C3A2002_0.OK, "Allocator level 3, " &
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285 "local access type");
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286
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287 A_Is_Level_1 (new C3A2002_0.Desig, Res);
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288 Display_Results (Res, C3A2002_0.P_E, "Allocator level 3, " &
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289 "level 1 access type");
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290
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291 end Block_L2;
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292
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293 Report.Result;
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294
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295 end C3A2002;
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