File : s-excmac-gcc.ads
1 ------------------------------------------------------------------------------
2 -- --
3 -- GNAT COMPILER COMPONENTS --
4 -- --
5 -- S Y S T E M . E X C E P T I O N S . M A C H I N E --
6 -- --
7 -- S p e c --
8 -- --
9 -- Copyright (C) 2013-2014, Free Software Foundation, Inc. --
10 -- --
11 -- GNAT is free software; you can redistribute it and/or modify it under --
12 -- terms of the GNU General Public License as published by the Free Soft- --
13 -- ware Foundation; either version 3, or (at your option) any later ver- --
14 -- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
15 -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
16 -- or FITNESS FOR A PARTICULAR PURPOSE. --
17 -- --
18 -- --
19 -- --
20 -- --
21 -- --
22 -- You should have received a copy of the GNU General Public License and --
23 -- a copy of the GCC Runtime Library Exception along with this program; --
24 -- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see --
25 -- <http://www.gnu.org/licenses/>. --
26 -- --
27 -- GNAT was originally developed by the GNAT team at New York University. --
28 -- Extensive contributions were provided by Ada Core Technologies Inc. --
29 -- --
30 ------------------------------------------------------------------------------
31
32 -- Declaration of the machine exception and some associated facilities. The
33 -- machine exception is the object that is propagated by low level routines
34 -- and that contains the Ada exception occurrence.
35
36 -- This is the version using the GCC EH mechanism
37
38 with Ada.Unchecked_Conversion;
39 with Ada.Exceptions;
40
41 package System.Exceptions.Machine is
42 pragma Preelaborate;
43
44 ------------------------------------------------
45 -- Entities to interface with the GCC runtime --
46 ------------------------------------------------
47
48 -- These come from "C++ ABI for Itanium: Exception handling", which is
49 -- the reference for GCC.
50
51 -- Return codes from the GCC runtime functions used to propagate
52 -- an exception.
53
54 type Unwind_Reason_Code is
55 (URC_NO_REASON,
56 URC_FOREIGN_EXCEPTION_CAUGHT,
57 URC_PHASE2_ERROR,
58 URC_PHASE1_ERROR,
59 URC_NORMAL_STOP,
60 URC_END_OF_STACK,
61 URC_HANDLER_FOUND,
62 URC_INSTALL_CONTEXT,
63 URC_CONTINUE_UNWIND);
64
65 pragma Unreferenced
66 (URC_NO_REASON,
67 URC_FOREIGN_EXCEPTION_CAUGHT,
68 URC_PHASE2_ERROR,
69 URC_PHASE1_ERROR,
70 URC_NORMAL_STOP,
71 URC_END_OF_STACK,
72 URC_HANDLER_FOUND,
73 URC_INSTALL_CONTEXT,
74 URC_CONTINUE_UNWIND);
75
76 pragma Convention (C, Unwind_Reason_Code);
77
78 -- Phase identifiers
79
80 type Unwind_Action is new Integer;
81 pragma Convention (C, Unwind_Action);
82
83 UA_SEARCH_PHASE : constant Unwind_Action := 1;
84 UA_CLEANUP_PHASE : constant Unwind_Action := 2;
85 UA_HANDLER_FRAME : constant Unwind_Action := 4;
86 UA_FORCE_UNWIND : constant Unwind_Action := 8;
87 UA_END_OF_STACK : constant Unwind_Action := 16; -- GCC extension
88
89 pragma Unreferenced
90 (UA_SEARCH_PHASE,
91 UA_CLEANUP_PHASE,
92 UA_HANDLER_FRAME,
93 UA_FORCE_UNWIND,
94 UA_END_OF_STACK);
95
96 -- Mandatory common header for any exception object handled by the
97 -- GCC unwinding runtime.
98
99 type Exception_Class is mod 2 ** 64;
100
101 GNAT_Exception_Class : constant Exception_Class := 16#474e552d41646100#;
102 -- "GNU-Ada\0"
103
104 type Unwind_Word is mod 2 ** System.Word_Size;
105 for Unwind_Word'Size use System.Word_Size;
106 -- Map the corresponding C type used in Unwind_Exception below
107
108 type Unwind_Exception is record
109 Class : Exception_Class;
110 Cleanup : System.Address;
111 Private1 : Unwind_Word;
112 Private2 : Unwind_Word;
113
114 -- Usual exception structure has only two private fields, but the SEH
115 -- one has six. To avoid making this file more complex, we use six
116 -- fields on all platforms, wasting a few bytes on some.
117
118 Private3 : Unwind_Word;
119 Private4 : Unwind_Word;
120 Private5 : Unwind_Word;
121 Private6 : Unwind_Word;
122 end record;
123 pragma Convention (C, Unwind_Exception);
124 -- Map the GCC struct used for exception handling
125
126 for Unwind_Exception'Alignment use Standard'Maximum_Alignment;
127 -- The C++ ABI mandates the common exception header to be at least
128 -- doubleword aligned, and the libGCC implementation actually makes it
129 -- maximally aligned (see unwind.h). See additional comments on the
130 -- alignment below.
131
132 -- There is a subtle issue with the common header alignment, since the C
133 -- version is aligned on BIGGEST_ALIGNMENT, the Ada version is aligned on
134 -- Standard'Maximum_Alignment, and those two values don't quite represent
135 -- the same concepts and so may be decoupled someday. One typical reason
136 -- is that BIGGEST_ALIGNMENT may be larger than what the underlying system
137 -- allocator guarantees, and there are extra costs involved in allocating
138 -- objects aligned to such factors.
139
140 -- To deal with the potential alignment differences between the C and Ada
141 -- representations, the Ada part of the whole structure is only accessed
142 -- by the personality routine through accessors. Ada specific fields are
143 -- thus always accessed through consistent layout, and we expect the
144 -- actual alignment to always be large enough to avoid traps from the C
145 -- accesses to the common header. Besides, accessors alleviate the need
146 -- for a C struct whole counterpart, both painful and error-prone to
147 -- maintain anyway.
148
149 type GCC_Exception_Access is access all Unwind_Exception;
150 -- Pointer to a GCC exception
151
152 procedure Unwind_DeleteException (Excp : not null GCC_Exception_Access);
153 pragma Import (C, Unwind_DeleteException, "_Unwind_DeleteException");
154 -- Procedure to free any GCC exception
155
156 --------------------------------------------------------------
157 -- GNAT Specific Entities To Deal With The GCC EH Circuitry --
158 --------------------------------------------------------------
159
160 -- A GNAT exception object to be dealt with by the personality routine
161 -- called by the GCC unwinding runtime.
162
163 type GNAT_GCC_Exception is record
164 Header : Unwind_Exception;
165 -- ABI Exception header first
166
167 Occurrence : aliased Ada.Exceptions.Exception_Occurrence;
168 -- The Ada occurrence
169 end record;
170
171 pragma Convention (C, GNAT_GCC_Exception);
172
173 type GNAT_GCC_Exception_Access is access all GNAT_GCC_Exception;
174
175 function To_GCC_Exception is new
176 Ada.Unchecked_Conversion (System.Address, GCC_Exception_Access);
177
178 function To_GNAT_GCC_Exception is new
179 Ada.Unchecked_Conversion
180 (GCC_Exception_Access, GNAT_GCC_Exception_Access);
181
182 function New_Occurrence return GNAT_GCC_Exception_Access is
183 (new GNAT_GCC_Exception'
184 (Header => (Class => GNAT_Exception_Class,
185 Cleanup => Null_Address,
186 others => 0),
187 Occurrence => <>));
188 -- Allocate and initialize a machine occurrence
189
190 end System.Exceptions.Machine;