xref: /freebsd/contrib/libcxxrt/cxxabi.h (revision d6b92ffa)
1 /*
2  * Copyright 2012 David Chisnall. All rights reserved.
3  *
4  * Permission is hereby granted, free of charge, to any person obtaining a copy
5  * of this software and associated documentation files (the "Software"), to
6  * deal in the Software without restriction, including without limitation the
7  * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
8  * sell copies of the Software, and to permit persons to whom the Software is
9  * furnished to do so, subject to the following conditions:
10  *
11  * The above copyright notice and this permission notice shall be
12  * included in all copies or substantial portions of the Software.
13  *
14  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
15  * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
16  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
17  * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
18  * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
19  * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
20  * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
21  */
22 
23 #ifndef __CXXABI_H_
24 #define __CXXABI_H_
25 #include <stddef.h>
26 #include <stdint.h>
27 #include "unwind.h"
28 namespace std
29 {
30 	class type_info;
31 }
32 /*
33  * The cxxabi.h header provides a set of public definitions for types and
34  * functions defined by the Itanium C++ ABI specification.  For reference, see
35  * the ABI specification here:
36  *
37  * http://sourcery.mentor.com/public/cxx-abi/abi.html
38  *
39  * All deviations from this specification, unless otherwise noted, are
40  * accidental.
41  */
42 
43 #ifdef __cplusplus
44 namespace __cxxabiv1 {
45 extern "C" {
46 #endif
47 /**
48  * Function type to call when an unexpected exception is encountered.
49  */
50 typedef void (*unexpected_handler)();
51 /**
52  * Function type to call when an unrecoverable condition is encountered.
53  */
54 typedef void (*terminate_handler)();
55 
56 
57 /**
58  * Structure used as a header on thrown exceptions.  This is the same layout as
59  * defined by the Itanium ABI spec, so should be interoperable with any other
60  * implementation of this spec, such as GNU libsupc++.
61  *
62  * This structure is allocated when an exception is thrown.  Unwinding happens
63  * in two phases, the first looks for a handler and the second installs the
64  * context.  This structure stores a cache of the handler location between
65  * phase 1 and phase 2.  Unfortunately, cleanup information is not cached, so
66  * must be looked up in both phases.  This happens for two reasons.  The first
67  * is that we don't know how many frames containing cleanups there will be, and
68  * we should avoid dynamic allocation during unwinding (the exception may be
69  * reporting that we've run out of memory).  The second is that finding
70  * cleanups is much cheaper than finding handlers, because we don't have to
71  * look at the type table at all.
72  *
73  * Note: Several fields of this structure have not-very-informative names.
74  * These are taken from the ABI spec and have not been changed to make it
75  * easier for people referring to to the spec while reading this code.
76  */
77 struct __cxa_exception
78 {
79 #if __LP64__
80 	/**
81 	 * Reference count.  Used to support the C++11 exception_ptr class.  This
82 	 * is prepended to the structure in 64-bit mode and squeezed in to the
83 	 * padding left before the 64-bit aligned _Unwind_Exception at the end in
84 	 * 32-bit mode.
85 	 *
86 	 * Note that it is safe to extend this structure at the beginning, rather
87 	 * than the end, because the public API for creating it returns the address
88 	 * of the end (where the exception object can be stored).
89 	 */
90 	uintptr_t referenceCount;
91 #endif
92 	/** Type info for the thrown object. */
93 	std::type_info *exceptionType;
94 	/** Destructor for the object, if one exists. */
95 	void (*exceptionDestructor) (void *);
96 	/** Handler called when an exception specification is violated. */
97 	unexpected_handler unexpectedHandler;
98 	/** Hander called to terminate. */
99 	terminate_handler terminateHandler;
100 	/**
101 	 * Next exception in the list.  If an exception is thrown inside a catch
102 	 * block and caught in a nested catch, this points to the exception that
103 	 * will be handled after the inner catch block completes.
104 	 */
105 	__cxa_exception *nextException;
106 	/**
107 	 * The number of handlers that currently have references to this
108 	 * exception.  The top (non-sign) bit of this is used as a flag to indicate
109 	 * that the exception is being rethrown, so should not be deleted when its
110 	 * handler count reaches 0 (which it doesn't with the top bit set).
111 	 */
112 	int handlerCount;
113 #if defined(__arm__) && !defined(__ARM_DWARF_EH__)
114 	/**
115 	 * The ARM EH ABI requires the unwind library to keep track of exceptions
116 	 * during cleanups.  These support nesting, so we need to keep a list of
117 	 * them.
118 	 */
119 	_Unwind_Exception *nextCleanup;
120 	/**
121 	 * The number of cleanups that are currently being run on this exception.
122 	 */
123 	int cleanupCount;
124 #endif
125 	/**
126 	 * The selector value to be returned when installing the catch handler.
127 	 * Used at the call site to determine which catch() block should execute.
128 	 * This is found in phase 1 of unwinding then installed in phase 2.
129 	 */
130 	int handlerSwitchValue;
131 	/**
132 	 * The action record for the catch.  This is cached during phase 1
133 	 * unwinding.
134 	 */
135 	const char *actionRecord;
136 	/**
137 	 * Pointer to the language-specific data area (LSDA) for the handler
138 	 * frame.  This is unused in this implementation, but set for ABI
139 	 * compatibility in case we want to mix code in very weird ways.
140 	 */
141 	const char *languageSpecificData;
142 	/** The cached landing pad for the catch handler.*/
143 	void *catchTemp;
144 	/**
145 	 * The pointer that will be returned as the pointer to the object.  When
146 	 * throwing a class and catching a virtual superclass (for example), we
147 	 * need to adjust the thrown pointer to make it all work correctly.
148 	 */
149 	void *adjustedPtr;
150 #if !__LP64__
151 	/**
152 	 * Reference count.  Used to support the C++11 exception_ptr class.  This
153 	 * is prepended to the structure in 64-bit mode and squeezed in to the
154 	 * padding left before the 64-bit aligned _Unwind_Exception at the end in
155 	 * 32-bit mode.
156 	 *
157 	 * Note that it is safe to extend this structure at the beginning, rather
158 	 * than the end, because the public API for creating it returns the address
159 	 * of the end (where the exception object can be stored)
160 	 */
161 	uintptr_t referenceCount;
162 #endif
163 	/** The language-agnostic part of the exception header. */
164 	_Unwind_Exception unwindHeader;
165 };
166 
167 /**
168  * ABI-specified globals structure.  Returned by the __cxa_get_globals()
169  * function and its fast variant.  This is a per-thread structure - every
170  * thread will have one lazily allocated.
171  *
172  * This structure is defined by the ABI, so may be used outside of this
173  * library.
174  */
175 struct __cxa_eh_globals
176 {
177 	/**
178 	 * A linked list of exceptions that are currently caught.  There may be
179 	 * several of these in nested catch() blocks.
180 	 */
181 	__cxa_exception *caughtExceptions;
182 	/**
183 	 * The number of uncaught exceptions.
184 	 */
185 	unsigned int uncaughtExceptions;
186 };
187 /**
188  * ABI function returning the __cxa_eh_globals structure.
189  */
190 __cxa_eh_globals *__cxa_get_globals(void);
191 /**
192  * Version of __cxa_get_globals() assuming that __cxa_get_globals() has already
193  * been called at least once by this thread.
194  */
195 __cxa_eh_globals *__cxa_get_globals_fast(void);
196 
197 std::type_info * __cxa_current_exception_type();
198 
199 /**
200  * Throws an exception returned by __cxa_current_primary_exception().  This
201  * exception may have been caught in another thread.
202  */
203 void __cxa_rethrow_primary_exception(void* thrown_exception);
204 /**
205  * Returns the current exception in a form that can be stored in an
206  * exception_ptr object and then rethrown by a call to
207  * __cxa_rethrow_primary_exception().
208  */
209 void *__cxa_current_primary_exception(void);
210 /**
211  * Increments the reference count of an exception.  Called when an
212  * exception_ptr is copied.
213  */
214 void __cxa_increment_exception_refcount(void* thrown_exception);
215 /**
216  * Decrements the reference count of an exception.  Called when an
217  * exception_ptr is deleted.
218  */
219 void __cxa_decrement_exception_refcount(void* thrown_exception);
220 /**
221  * Demangles a C++ symbol or type name.  The buffer, if non-NULL, must be
222  * allocated with malloc() and must be *n bytes or more long.  This function
223  * may call realloc() on the value pointed to by buf, and will return the
224  * length of the string via *n.
225  *
226  * The value pointed to by status is set to one of the following:
227  *
228  * 0: success
229  * -1: memory allocation failure
230  * -2: invalid mangled name
231  * -3: invalid arguments
232  */
233 char* __cxa_demangle(const char* mangled_name,
234                      char* buf,
235                      size_t* n,
236                      int* status);
237 #ifdef __cplusplus
238 } // extern "C"
239 } // namespace
240 
241 namespace abi = __cxxabiv1;
242 
243 #endif /* __cplusplus */
244 #endif /* __CXXABI_H_ */
245