GCC Middle and Back End API Reference
except.h
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1 /* Exception Handling interface routines.
2  Copyright (C) 1996-2013 Free Software Foundation, Inc.
3  Contributed by Mike Stump <mrs@cygnus.com>.
4 
5 This file is part of GCC.
6 
7 GCC is free software; you can redistribute it and/or modify it under
8 the terms of the GNU General Public License as published by the Free
9 Software Foundation; either version 3, or (at your option) any later
10 version.
11 
12 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
13 WARRANTY; without even the implied warranty of MERCHANTABILITY or
14 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
15 for more details.
16 
17 You should have received a copy of the GNU General Public License
18 along with GCC; see the file COPYING3. If not see
19 <http://www.gnu.org/licenses/>. */
20 
21 /* No include guards here, but define an include file marker anyway, so
22  that the compiler can keep track of where this file is included. This
23  is e.g. used to avoid including this file in front-end specific files. */
24 #ifndef GCC_EXCEPT_H
25 # define GCC_EXCEPT_H
26 #endif
27 
28 #include "hashtab.h"
29 
30 struct function;
31 struct eh_region_d;
32 struct pointer_map_t;
33 
34 /* The type of an exception region. */
35 enum eh_region_type
36 {
37  /* CLEANUP regions implement e.g. destructors run when exiting a block.
38  They can be generated from both GIMPLE_TRY_FINALLY and GIMPLE_TRY_CATCH
39  nodes. It is expected by the runtime that cleanup regions will *not*
40  resume normal program flow, but will continue propagation of the
41  exception. */
43 
44  /* TRY regions implement catching an exception. The list of types associated
45  with the attached catch handlers is examined in order by the runtime and
46  control is transferred to the appropriate handler. Note that a NULL type
47  list is a catch-all handler, and that it will catch *all* exceptions
48  including those originating from a different language. */
49  ERT_TRY,
50 
51  /* ALLOWED_EXCEPTIONS regions implement exception filtering, e.g. the
52  throw(type-list) specification that can be added to C++ functions.
53  The runtime examines the thrown exception vs the type list, and if
54  the exception does not match, transfers control to the handler. The
55  normal handler for C++ calls __cxa_call_unexpected. */
57 
58  /* MUST_NOT_THROW regions prevent all exceptions from propagating. This
59  region type is used in C++ to surround destructors being run inside a
60  CLEANUP region. This differs from an ALLOWED_EXCEPTIONS region with
61  an empty type list in that the runtime is prepared to terminate the
62  program directly. We only generate code for MUST_NOT_THROW regions
63  along control paths that are already handling an exception within the
64  current function. */
66 };
67 
68 
69 /* A landing pad for a given exception region. Any transfer of control
70  from the EH runtime to the function happens at a landing pad. */
71 
73 {
74  /* The linked list of all landing pads associated with the region. */
75  struct eh_landing_pad_d *next_lp;
76 
77  /* The region with which this landing pad is associated. */
78  struct eh_region_d *region;
79 
80  /* At the gimple level, the location to which control will be transferred
81  for this landing pad. There can be both EH and normal edges into the
82  block containing the post-landing-pad label. */
83  tree post_landing_pad;
84 
85  /* At the rtl level, the location to which the runtime will transfer
86  control. This differs from the post-landing-pad in that the target's
87  EXCEPTION_RECEIVER pattern will be expanded here, as well as other
88  bookkeeping specific to exceptions. There must not be normal edges
89  into the block containing the landing-pad label. */
90  rtx landing_pad;
91 
92  /* The index of this landing pad within fun->eh->lp_array. */
93  int index;
94 };
95 
96 /* A catch handler associated with an ERT_TRY region. */
97 
98 struct GTY(()) eh_catch_d
99 {
100  /* The double-linked list of all catch handlers for the region. */
101  struct eh_catch_d *next_catch;
103 
104  /* A TREE_LIST of runtime type objects that this catch handler
105  will catch, or NULL if all exceptions are caught. */
107 
108  /* A TREE_LIST of INTEGER_CSTs that correspond to the type_list entries,
109  having been mapped by assign_filter_values. These integers are to be
110  compared against the __builtin_eh_filter value. */
113  /* The code that should be executed if this catch handler matches the
114  thrown exception. This label is only maintained until
115  pass_lower_eh_dispatch, at which point it is cleared. */
117 };
118 
119 /* Describes one exception region. */
120 
121 struct GTY(()) eh_region_d
122 {
123  /* The immediately surrounding region. */
124  struct eh_region_d *outer;
125 
126  /* The list of immediately contained regions. */
127  struct eh_region_d *inner;
129 
130  /* The index of this region within fun->eh->region_array. */
131  int index;
132 
133  /* Each region does exactly one thing. */
135 
136  /* Holds the action to perform based on the preceding type. */
137  union eh_region_u {
138  struct eh_region_u_try {
139  /* The double-linked list of all catch handlers for this region. */
140  struct eh_catch_d *first_catch;
141  struct eh_catch_d *last_catch;
142  } GTY ((tag ("ERT_TRY"))) eh_try;
143 
144  struct eh_region_u_allowed {
145  /* A TREE_LIST of runtime type objects allowed to pass. */
146  tree type_list;
147  /* The code that should be executed if the thrown exception does
148  not match the type list. This label is only maintained until
149  pass_lower_eh_dispatch, at which point it is cleared. */
150  tree label;
151  /* The integer that will be passed by the runtime to signal that
152  we should execute the code at LABEL. This integer is assigned
153  by assign_filter_values and is to be compared against the
154  __builtin_eh_filter value. */
155  int filter;
156  } GTY ((tag ("ERT_ALLOWED_EXCEPTIONS"))) allowed;
158  struct eh_region_u_must_not_throw {
159  /* A function decl to be invoked if this region is actually reachable
160  from within the function, rather than implementable from the runtime.
161  The normal way for this to happen is for there to be a CLEANUP region
162  contained within this MUST_NOT_THROW region. Note that if the
163  runtime handles the MUST_NOT_THROW region, we have no control over
164  what termination function is called; it will be decided by the
165  personality function in effect for this CIE. */
166  tree failure_decl;
167  /* The location assigned to the call of FAILURE_DECL, if expanded. */
168  location_t failure_loc;
169  } GTY ((tag ("ERT_MUST_NOT_THROW"))) must_not_throw;
170  } GTY ((desc ("%0.type"))) u;
171 
172  /* The list of landing pads associated with this region. */
173  struct eh_landing_pad_d *landing_pads;
174 
175  /* EXC_PTR and FILTER values copied from the runtime for this region.
176  Each region gets its own psuedos so that if there are nested exceptions
177  we do not overwrite the values of the first exception. */
178  rtx exc_ptr_reg, filter_reg;
179 
180  /* True if this region should use __cxa_end_cleanup instead
181  of _Unwind_Resume. */
182  bool use_cxa_end_cleanup;
183 };
184 
185 typedef struct eh_landing_pad_d *eh_landing_pad;
186 typedef struct eh_catch_d *eh_catch;
187 typedef struct eh_region_d *eh_region;
188 
189 
190 
191 
192 /* The exception status for each function. */
193 
194 struct GTY(()) eh_status
195 {
196  /* The tree of all regions for this function. */
197  eh_region region_tree;
199  /* The same information as an indexable array. */
200  vec<eh_region, va_gc> *region_array;
201 
202  /* The landing pads as an indexable array. */
203  vec<eh_landing_pad, va_gc> *lp_array;
205  /* At the gimple level, a mapping from gimple statement to landing pad
206  or must-not-throw region. See record_stmt_eh_region. */
207  htab_t GTY((param_is (struct throw_stmt_node))) throw_stmt_table;
208 
209  /* All of the runtime type data used by the function. These objects
210  are emitted to the lang-specific-data-area for the function. */
211  vec<tree, va_gc> *ttype_data;
212 
213  /* The table of all action chains. These encode the eh_region tree in
214  a compact form for use by the runtime, and is also emitted to the
215  lang-specific-data-area. Note that the ARM EABI uses a different
216  format for the encoding than all other ports. */
217  union eh_status_u {
218  vec<tree, va_gc> *GTY((tag ("1"))) arm_eabi;
219  vec<uchar, va_gc> *GTY((tag ("0"))) other;
220  } GTY ((desc ("targetm.arm_eabi_unwinder"))) ehspec_data;
221 };
222 
223 
224 /* Invokes CALLBACK for every exception handler label. Only used by old
225  loop hackery; should not be used by new code. */
226 extern void for_each_eh_label (void (*) (rtx));
227 
228 extern void init_eh_for_function (void);
229 
230 extern void remove_eh_landing_pad (eh_landing_pad);
231 extern void remove_eh_handler (eh_region);
233 
234 extern bool current_function_has_exception_handlers (void);
235 extern void output_function_exception_table (const char *);
237 extern rtx expand_builtin_eh_pointer (tree);
238 extern rtx expand_builtin_eh_filter (tree);
239 extern rtx expand_builtin_eh_copy_values (tree);
240 extern void expand_builtin_unwind_init (void);
241 extern rtx expand_builtin_eh_return_data_regno (tree);
242 extern rtx expand_builtin_extract_return_addr (tree);
243 extern void expand_builtin_init_dwarf_reg_sizes (tree);
244 extern rtx expand_builtin_frob_return_addr (tree);
246 extern void expand_builtin_eh_return (tree, tree);
247 extern void expand_eh_return (void);
248 extern rtx expand_builtin_extend_pointer (tree);
249 extern void expand_dw2_landing_pad_for_region (eh_region);
251 typedef tree (*duplicate_eh_regions_map) (tree, void *);
252 extern struct pointer_map_t *duplicate_eh_regions
253  (struct function *, eh_region, int, duplicate_eh_regions_map, void *);
254 
255 extern void sjlj_emit_function_exit_after (rtx);
256 
257 extern eh_region gen_eh_region_cleanup (eh_region);
258 extern eh_region gen_eh_region_try (eh_region);
259 extern eh_region gen_eh_region_allowed (eh_region, tree);
260 extern eh_region gen_eh_region_must_not_throw (eh_region);
261 
262 extern eh_catch gen_eh_region_catch (eh_region, tree);
263 extern eh_landing_pad gen_eh_landing_pad (eh_region);
264 
265 extern eh_region get_eh_region_from_number_fn (struct function *, int);
266 extern eh_region get_eh_region_from_number (int);
267 extern eh_landing_pad get_eh_landing_pad_from_number_fn (struct function*,int);
268 extern eh_landing_pad get_eh_landing_pad_from_number (int);
269 extern eh_region get_eh_region_from_lp_number_fn (struct function *, int);
270 extern eh_region get_eh_region_from_lp_number (int);
271 
272 extern eh_region eh_region_outermost (struct function *, eh_region, eh_region);
273 
274 extern void make_reg_eh_region_note (rtx insn, int ecf_flags, int lp_nr);
276 
277 extern void verify_eh_tree (struct function *);
278 extern void dump_eh_tree (FILE *, struct function *);
279 void debug_eh_tree (struct function *);
280 extern void add_type_for_runtime (tree);
281 extern tree lookup_type_for_runtime (tree);
282 extern void assign_filter_values (void);
283 
284 extern eh_region get_eh_region_from_rtx (const_rtx);
285 extern eh_landing_pad get_eh_landing_pad_from_rtx (const_rtx);
286 
287 extern void finish_eh_generation (void);
288 
289 struct GTY(()) throw_stmt_node {
290  gimple stmt;
291  int lp_nr;
292 };
293 
294 extern struct htab *get_eh_throw_stmt_table (struct function *);
295 extern void set_eh_throw_stmt_table (struct function *, struct htab *);
296 
297 enum eh_personality_kind {
301 };
302 
303 extern enum eh_personality_kind
304 function_needs_eh_personality (struct function *);
305 
306 /* Pre-order iteration within the eh_region tree. */
307 
308 static inline eh_region
309 ehr_next (eh_region r, eh_region start)
310 {
311  if (r->inner)
312  r = r->inner;
313  else if (r->next_peer && r != start)
314  r = r->next_peer;
315  else
316  {
317  do
318  {
319  r = r->outer;
320  if (r == start)
321  return NULL;
322  }
323  while (r->next_peer == NULL);
324  r = r->next_peer;
325  }
326  return r;
327 }
328 
329 #define FOR_ALL_EH_REGION_AT(R, START) \
330  for ((R) = (START); (R) != NULL; (R) = ehr_next (R, START))
332 #define FOR_ALL_EH_REGION_FN(R, FN) \
333  for ((R) = (FN)->eh->region_tree; (R) != NULL; (R) = ehr_next (R, NULL))
334 
335 #define FOR_ALL_EH_REGION(R) FOR_ALL_EH_REGION_FN (R, cfun)