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1 ------------------------------------------------------------------------------
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2 -- --
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3 -- GNAT RUN-TIME COMPONENTS --
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4 -- --
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5 -- A D A . E X C E P T I O N S --
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6 -- --
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7 -- S p e c --
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8 -- --
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131
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9 -- Copyright (C) 1992-2018, Free Software Foundation, Inc. --
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111
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10 -- --
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11 -- This specification is derived from the Ada Reference Manual for use with --
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12 -- GNAT. The copyright notice above, and the license provisions that follow --
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13 -- apply solely to the contents of the part following the private keyword. --
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14 -- --
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15 -- GNAT is free software; you can redistribute it and/or modify it under --
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16 -- terms of the GNU General Public License as published by the Free Soft- --
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17 -- ware Foundation; either version 3, or (at your option) any later ver- --
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18 -- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
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19 -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
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20 -- or FITNESS FOR A PARTICULAR PURPOSE. --
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21 -- --
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22 -- As a special exception under Section 7 of GPL version 3, you are granted --
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23 -- additional permissions described in the GCC Runtime Library Exception, --
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24 -- version 3.1, as published by the Free Software Foundation. --
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25 -- --
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26 -- You should have received a copy of the GNU General Public License and --
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27 -- a copy of the GCC Runtime Library Exception along with this program; --
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28 -- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see --
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29 -- <http://www.gnu.org/licenses/>. --
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30 -- --
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31 -- GNAT was originally developed by the GNAT team at New York University. --
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32 -- Extensive contributions were provided by Ada Core Technologies Inc. --
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33 -- --
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34 ------------------------------------------------------------------------------
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35
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36 -- This version of Ada.Exceptions fully supports Ada 95 and later language
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37 -- versions. It is used in all situations except for the build of the
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38 -- compiler and other basic tools. For these latter builds, we use an
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39 -- Ada 95-only version.
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40
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41 -- The reason for this splitting off of a separate version is to support
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42 -- older bootstrap compilers that do not support Ada 2005 features, and
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43 -- Ada.Exceptions is part of the compiler sources.
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44
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45 pragma Polling (Off);
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46 -- We must turn polling off for this unit, because otherwise we get
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47 -- elaboration circularities with ourself.
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48
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49 with System;
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50 with System.Parameters;
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51 with System.Standard_Library;
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52 with System.Traceback_Entries;
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53
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54 package Ada.Exceptions is
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55 pragma Preelaborate;
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56 -- In accordance with Ada 2005 AI-362.
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57
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58 type Exception_Id is private;
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59 pragma Preelaborable_Initialization (Exception_Id);
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60
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61 Null_Id : constant Exception_Id;
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62
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63 type Exception_Occurrence is limited private;
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64 pragma Preelaborable_Initialization (Exception_Occurrence);
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65
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66 type Exception_Occurrence_Access is access all Exception_Occurrence;
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67
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68 Null_Occurrence : constant Exception_Occurrence;
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69
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70 function Exception_Name (Id : Exception_Id) return String;
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71
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72 function Exception_Name (X : Exception_Occurrence) return String;
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73
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74 function Wide_Exception_Name
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75 (Id : Exception_Id) return Wide_String;
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76 pragma Ada_05 (Wide_Exception_Name);
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77
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78 function Wide_Exception_Name
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79 (X : Exception_Occurrence) return Wide_String;
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80 pragma Ada_05 (Wide_Exception_Name);
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81
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82 function Wide_Wide_Exception_Name
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83 (Id : Exception_Id) return Wide_Wide_String;
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84 pragma Ada_05 (Wide_Wide_Exception_Name);
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85
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86 function Wide_Wide_Exception_Name
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87 (X : Exception_Occurrence) return Wide_Wide_String;
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88 pragma Ada_05 (Wide_Wide_Exception_Name);
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89
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90 procedure Raise_Exception (E : Exception_Id; Message : String := "");
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91 pragma No_Return (Raise_Exception);
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92 -- Note: In accordance with AI-466, CE is raised if E = Null_Id
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93
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94 function Exception_Message (X : Exception_Occurrence) return String;
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95
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96 procedure Reraise_Occurrence (X : Exception_Occurrence);
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97 -- Note: it would be really nice to give a pragma No_Return for this
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98 -- procedure, but it would be wrong, since Reraise_Occurrence does return
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99 -- if the argument is the null exception occurrence. See also procedure
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100 -- Reraise_Occurrence_Always in the private part of this package.
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101
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102 function Exception_Identity (X : Exception_Occurrence) return Exception_Id;
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103
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104 function Exception_Information (X : Exception_Occurrence) return String;
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105 -- The format of the exception information is as follows:
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106 --
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107 -- exception name (as in Exception_Name)
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108 -- message (or a null line if no message)
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109 -- PID=nnnn
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110 -- 0xyyyyyyyy 0xyyyyyyyy ...
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111 --
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112 -- The lines are separated by a ASCII.LF character
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113 --
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114 -- The nnnn is the partition Id given as decimal digits
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115 --
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116 -- The 0x... line represents traceback program counter locations,
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117 -- in order with the first one being the exception location.
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118
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119 -- Note on ordering: the compiler uses the Save_Occurrence procedure, but
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120 -- not the function from Rtsfind, so it is important that the procedure
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121 -- come first, since Rtsfind finds the first matching entity.
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122
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123 procedure Save_Occurrence
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124 (Target : out Exception_Occurrence;
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125 Source : Exception_Occurrence);
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126
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127 function Save_Occurrence
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128 (Source : Exception_Occurrence)
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129 return Exception_Occurrence_Access;
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130
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131 -- Ada 2005 (AI-438): The language revision introduces the following
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132 -- subprograms and attribute definitions. We do not provide them
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133 -- explicitly. instead, the corresponding stream attributes are made
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134 -- available through a pragma Stream_Convert in the private part.
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135
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136 -- procedure Read_Exception_Occurrence
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137 -- (Stream : not null access Ada.Streams.Root_Stream_Type'Class;
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138 -- Item : out Exception_Occurrence);
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139
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140 -- procedure Write_Exception_Occurrence
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141 -- (Stream : not null access Ada.Streams.Root_Stream_Type'Class;
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142 -- Item : Exception_Occurrence);
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143
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144 -- for Exception_Occurrence'Read use Read_Exception_Occurrence;
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145 -- for Exception_Occurrence'Write use Write_Exception_Occurrence;
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146
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147 private
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148 package SSL renames System.Standard_Library;
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149 package SP renames System.Parameters;
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150
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151 subtype EOA is Exception_Occurrence_Access;
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152
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153 Exception_Msg_Max_Length : constant := SP.Default_Exception_Msg_Max_Length;
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154
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155 ------------------
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156 -- Exception_Id --
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157 ------------------
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158
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159 subtype Code_Loc is System.Address;
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160 -- Code location used in building exception tables and for call addresses
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161 -- when propagating an exception. Values of this type are created by using
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162 -- Label'Address or extracted from machine states using Get_Code_Loc.
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163
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164 Null_Loc : constant Code_Loc := System.Null_Address;
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165 -- Null code location, used to flag outer level frame
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166
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167 type Exception_Id is new SSL.Exception_Data_Ptr;
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168
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169 function EId_To_String (X : Exception_Id) return String;
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170 function String_To_EId (S : String) return Exception_Id;
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171 pragma Stream_Convert (Exception_Id, String_To_EId, EId_To_String);
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172 -- Functions for implementing Exception_Id stream attributes
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173
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174 Null_Id : constant Exception_Id := null;
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175
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176 -------------------------
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177 -- Private Subprograms --
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178 -------------------------
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179
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180 function Exception_Name_Simple (X : Exception_Occurrence) return String;
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181 -- Like Exception_Name, but returns the simple non-qualified name of the
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182 -- exception. This is used to implement the Exception_Name function in
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183 -- Current_Exceptions (the DEC compatible unit). It is called from the
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184 -- compiler generated code (using Rtsfind, which does not respect the
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185 -- private barrier, so we can place this function in the private part
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186 -- where the compiler can find it, but the spec is unchanged.)
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187
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188 procedure Raise_Exception_Always (E : Exception_Id; Message : String := "");
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189 pragma No_Return (Raise_Exception_Always);
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190 pragma Export (Ada, Raise_Exception_Always, "__gnat_raise_exception");
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191 -- This differs from Raise_Exception only in that the caller has determined
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192 -- that for sure the parameter E is not null, and that therefore no check
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193 -- for Null_Id is required. The expander converts Raise_Exception calls to
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194 -- Raise_Exception_Always if it can determine this is the case. The Export
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195 -- allows this routine to be accessed from Pure units.
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196
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197 procedure Raise_From_Signal_Handler
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198 (E : Exception_Id;
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199 M : System.Address);
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200 pragma Export
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201 (Ada, Raise_From_Signal_Handler,
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202 "ada__exceptions__raise_from_signal_handler");
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203 pragma No_Return (Raise_From_Signal_Handler);
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204 -- This routine is used to raise an exception from a signal handler. The
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205 -- signal handler has already stored the machine state (i.e. the state that
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206 -- corresponds to the location at which the signal was raised). E is the
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207 -- Exception_Id specifying what exception is being raised, and M is a
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208 -- pointer to a null-terminated string which is the message to be raised.
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209 -- Note that this routine never returns, so it is permissible to simply
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210 -- jump to this routine, rather than call it. This may be appropriate for
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211 -- systems where the right way to get out of signal handler is to alter the
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212 -- PC value in the machine state or in some other way ask the operating
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213 -- system to return here rather than to the original location.
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214
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215 procedure Raise_From_Controlled_Operation
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216 (X : Ada.Exceptions.Exception_Occurrence);
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217 pragma No_Return (Raise_From_Controlled_Operation);
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218 pragma Export
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219 (Ada, Raise_From_Controlled_Operation,
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220 "__gnat_raise_from_controlled_operation");
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221 -- Raise Program_Error, providing information about X (an exception raised
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222 -- during a controlled operation) in the exception message.
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223
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224 procedure Reraise_Library_Exception_If_Any;
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225 pragma Export
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226 (Ada, Reraise_Library_Exception_If_Any,
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227 "__gnat_reraise_library_exception_if_any");
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228 -- If there was an exception raised during library-level finalization,
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229 -- reraise the exception.
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230
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231 procedure Reraise_Occurrence_Always (X : Exception_Occurrence);
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232 pragma No_Return (Reraise_Occurrence_Always);
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233 -- This differs from Raise_Occurrence only in that the caller guarantees
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234 -- that for sure the parameter X is not the null occurrence, and that
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235 -- therefore this procedure cannot return. The expander uses this routine
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236 -- in the translation of a raise statement with no parameter (reraise).
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237
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238 procedure Reraise_Occurrence_No_Defer (X : Exception_Occurrence);
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239 pragma No_Return (Reraise_Occurrence_No_Defer);
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240 -- Exactly like Reraise_Occurrence, except that abort is not deferred
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241 -- before the call and the parameter X is known not to be the null
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242 -- occurrence. This is used in generated code when it is known that abort
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243 -- is already deferred.
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244
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245 function Triggered_By_Abort return Boolean;
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246 -- Determine whether the current exception (if it exists) is an instance of
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247 -- Standard'Abort_Signal.
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248
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249 -----------------------
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250 -- Polling Interface --
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251 -----------------------
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252
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253 -- The GNAT compiler has an option to generate polling calls to the Poll
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254 -- routine in this package. Specifying the -gnatP option for a compilation
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255 -- causes a call to Ada.Exceptions.Poll to be generated on every subprogram
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256 -- entry and on every iteration of a loop, thus avoiding the possibility of
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257 -- a case of unbounded time between calls.
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258
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259 -- This polling interface may be used for instrumentation or debugging
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260 -- purposes (e.g. implementing watchpoints in software or in the debugger).
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261
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262 -- In the GNAT technology itself, this interface is used to implement
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263 -- immediate asynchronous transfer of control and immediate abort on
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264 -- targets which do not provide for one thread interrupting another.
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265
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266 -- Note: this used to be in a separate unit called System.Poll, but that
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267 -- caused horrible circular elaboration problems between System.Poll and
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268 -- Ada.Exceptions.
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269
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270 procedure Poll;
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271 -- Check for asynchronous abort. Note that we do not inline the body.
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272 -- This makes the interface more useful for debugging purposes.
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273
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274 --------------------------
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275 -- Exception_Occurrence --
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276 --------------------------
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277
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278 package TBE renames System.Traceback_Entries;
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279
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280 Max_Tracebacks : constant := 50;
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281 -- Maximum number of trace backs stored in exception occurrence
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282
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283 subtype Tracebacks_Array is TBE.Tracebacks_Array (1 .. Max_Tracebacks);
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284 -- Traceback array stored in exception occurrence
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285
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286 type Exception_Occurrence is record
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287 Id : Exception_Id;
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288 -- Exception_Identity for this exception occurrence
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289
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290 Machine_Occurrence : System.Address;
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291 -- The underlying machine occurrence. For GCC, this corresponds to the
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292 -- _Unwind_Exception structure address.
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293
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294 Msg_Length : Natural := 0;
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295 -- Length of message (zero = no message)
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296
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297 Msg : String (1 .. Exception_Msg_Max_Length);
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298 -- Characters of message
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299
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300 Exception_Raised : Boolean := False;
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301 -- Set to true to indicate that this exception occurrence has actually
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302 -- been raised. When an exception occurrence is first created, this is
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303 -- set to False, then when it is processed by Raise_Current_Exception,
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304 -- it is set to True. If Raise_Current_Exception is used to raise an
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305 -- exception for which this flag is already True, then it knows that
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306 -- it is dealing with the reraise case (which is useful to distinguish
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307 -- for exception tracing purposes).
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308
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309 Pid : Natural := 0;
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310 -- Partition_Id for partition raising exception
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311
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312 Num_Tracebacks : Natural range 0 .. Max_Tracebacks := 0;
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313 -- Number of traceback entries stored
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314
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315 Tracebacks : Tracebacks_Array;
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316 -- Stored tracebacks (in Tracebacks (1 .. Num_Tracebacks))
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317 end record;
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318
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319 function "=" (Left, Right : Exception_Occurrence) return Boolean
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320 is abstract;
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321 -- Don't allow comparison on exception occurrences, we should not need
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322 -- this, and it would not work right, because of the Msg and Tracebacks
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323 -- fields which have unused entries not copied by Save_Occurrence.
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324
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325 function Get_Exception_Machine_Occurrence
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326 (X : Exception_Occurrence) return System.Address;
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327 pragma Export (Ada, Get_Exception_Machine_Occurrence,
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328 "__gnat_get_exception_machine_occurrence");
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329 -- Get the machine occurrence corresponding to an exception occurrence.
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330 -- It is Null_Address if there is no machine occurrence (in runtimes that
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331 -- doesn't use GCC mechanism) or if it has been lost (Save_Occurrence
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332 -- doesn't save the machine occurrence).
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333
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334 function EO_To_String (X : Exception_Occurrence) return String;
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335 function String_To_EO (S : String) return Exception_Occurrence;
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336 pragma Stream_Convert (Exception_Occurrence, String_To_EO, EO_To_String);
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337 -- Functions for implementing Exception_Occurrence stream attributes
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338
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339 Null_Occurrence : constant Exception_Occurrence := (
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340 Id => null,
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341 Machine_Occurrence => System.Null_Address,
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342 Msg_Length => 0,
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343 Msg => (others => ' '),
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344 Exception_Raised => False,
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345 Pid => 0,
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346 Num_Tracebacks => 0,
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347 Tracebacks => (others => TBE.Null_TB_Entry));
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348
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349 end Ada.Exceptions;
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