gcc/except.h

   1 /* Exception Handling interface routines.
   2    Copyright (C) 1996, 1997, 1998, 1999, 2000 Free Software Foundation, Inc.
   3    Contributed by Mike Stump <mrs@cygnus.com>.
   4
   5 This file is part of GNU CC.
   6
   7 GNU CC is free software; you can redistribute it and/or modify
   8 it under the terms of the GNU General Public License as published by
   9 the Free Software Foundation; either version 2, or (at your option)
  10 any later version.
  11
  12 GNU CC is distributed in the hope that it will be useful,
  13 but WITHOUT ANY WARRANTY; without even the implied warranty of
  14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15 GNU General Public License for more details.
  16
  17 You should have received a copy of the GNU General Public License
  18 along with GNU CC; see the file COPYING.  If not, write to
  19 the Free Software Foundation, 59 Temple Place - Suite 330,
  20 Boston, MA 02111-1307, USA.  */
  21
  22 #if !defined(NULL_RTX) && !defined(rtx)
  23 typedef struct rtx_def *_except_rtx;
  24 #define rtx _except_rtx
  25 #endif
  26
  27 #ifdef TREE_CODE
  28
  29 /* A stack of labels. CHAIN points to the next entry in the stack.  */
  30
  31 struct label_node {
  32   union {
  33     rtx rlabel;
  34     tree tlabel;
  35   } u;
  36   struct label_node *chain;
  37 };
  38
  39 /* An eh_entry is used to describe one exception handling region.
  40
  41    OUTER_CONTEXT is the label used for rethrowing into the outer context.
  42
  43    EXCEPTION_HANDLER_LABEL is the label corresponding to the handler
  44    for this region.
  45
  46    LABEL_USED indicates whether a CATCH block has already used this
  47    label or not. New ones are needed for additional catch blocks if
  48    it has.
  49
  50    FALSE_LABEL is used when either setjmp/longjmp exceptions are in
  51    use, or old style table exceptions. It contains the label for
  52    branching to the next runtime type check as handlers are processed.
  53
  54    FINALIZATION is the tree codes for the handler, or is NULL_TREE if
  55    one hasn't been generated yet, or is integer_zero_node to mark the
  56    end of a group of try blocks.  */
  57
  58 struct eh_entry {
  59   rtx outer_context;
  60   rtx exception_handler_label;
  61   tree finalization;
  62   int label_used;
  63   rtx false_label;
  64   rtx rethrow_label;
  65   /* If non-zero, this entry is for a handler created when we left an
  66      exception-region via goto.  */
  67   unsigned goto_entry_p : 1;
  68 };
  69 #else
  70 struct label_node;
  71 struct eh_entry;
  72 #endif
  73
  74 /* A list of EH_ENTRYs. ENTRY is the entry; CHAIN points to the next
  75    entry in the list, or is NULL if this is the last entry.  */
  76
  77 struct eh_node {
  78   struct eh_entry *entry;
  79   struct eh_node *chain;
  80 };
  81
  82 /* A stack of EH_ENTRYs. TOP is the topmost entry on the stack. TOP is
  83    NULL if the stack is empty.  */
  84
  85 struct eh_stack {
  86   struct eh_node *top;
  87 };
  88
  89 /* A queue of EH_ENTRYs. HEAD is the front of the queue; TAIL is the
  90    end (the latest entry). HEAD and TAIL are NULL if the queue is
  91    empty.  */
  92
  93 struct eh_queue {
  94   struct eh_node *head;
  95   struct eh_node *tail;
  96   struct eh_queue *next;
  97 };
  98
  99 /* Used to save exception handling status for each function.  */
 100 struct eh_status
 101 {
 102   /* A stack used for keeping track of the currently active exception
 103      handling region.  As each exception region is started, an entry
 104      describing the region is pushed onto this stack.  The current
 105      region can be found by looking at the top of the stack, and as we
 106      exit regions, the corresponding entries are popped.
 107
 108      Entries cannot overlap; they can be nested. So there is only one
 109      entry at most that corresponds to the current instruction, and that
 110      is the entry on the top of the stack.  */
 111   struct eh_stack x_ehstack;
 112   /* This stack is used to represent what the current eh region is
 113      for the catch blocks beings processed */
 114   struct eh_stack x_catchstack;
 115   /* A queue used for tracking which exception regions have closed.
 116      As we exit a region, we enqueue a new entry. The entries are then
 117      dequeued during expand_leftover_cleanups and
 118      expand_start_all_catch.  */
 119   struct eh_queue *x_ehqueue;
 120   /* Insns for all of the exception handlers for the current function.
 121      They are currently emitted by the frontend code.  */
 122   rtx x_catch_clauses;
 123   /* End of exception handler insn sequence.  */
 124   rtx x_catch_clauses_last;
 125   /* A random data area for the front end's own use.  */
 126   struct label_node *x_false_label_stack;
 127   /* Keeps track of the label to resume to should one want to resume
 128      normal control flow out of a handler (instead of, say, returning to
 129      the caller of the current function or exiting the program).  */
 130   struct label_node *x_caught_return_label_stack;
 131   /* A stack (TREE_LIST) of lists of handlers.  The TREE_VALUE of each
 132      node is itself a TREE_CHAINed list of handlers for regions that
 133      are not yet closed. The TREE_VALUE of each entry contains the
 134      handler for the corresponding entry on the ehstack.  */
 135   union tree_node *x_protect_list;
 136   /* The EH context.  Nonzero if the function has already
 137      fetched a pointer to the EH context  for exception handling.  */
 138   rtx ehc;
 139   /* The label generated by expand_builtin_eh_return.  */
 140   rtx x_eh_return_stub_label;
 141 };
 142
 143 #define ehstack (cfun->eh->x_ehstack)
 144 #define catchstack (cfun->eh->x_catchstack)
 145 #define ehqueue (cfun->eh->x_ehqueue)
 146 #define catch_clauses (cfun->eh->x_catch_clauses)
 147 #define catch_clauses_last (cfun->eh->x_catch_clauses_last)
 148 #define false_label_stack (cfun->eh->x_false_label_stack)
 149 #define caught_return_label_stack (cfun->eh->x_caught_return_label_stack)
 150 #define protect_list (cfun->eh->x_protect_list)
 151 #define current_function_ehc (cfun->eh->ehc)
 152 #define eh_return_stub_label (cfun->eh->x_eh_return_stub_label)
 153
 154 #ifdef TREE_CODE
 155 /* Start an exception handling region.  All instructions emitted after
 156    this point are considered to be part of the region until
 157    expand_eh_region_end () is invoked.  */
 158
 159 extern void expand_eh_region_start              PARAMS ((void));
 160
 161 /* Just like expand_eh_region_start, except if a cleanup action is
 162    entered on the cleanup chain, the TREE_PURPOSE of the element put
 163    on the chain is DECL.  DECL should be the associated VAR_DECL, if
 164    any, otherwise it should be NULL_TREE.  */
 165
 166 extern void expand_eh_region_start_for_decl     PARAMS ((tree));
 167
 168 /* Start an exception handling region for the given cleanup action.
 169    All instructions emitted after this point are considered to be part
 170    of the region until expand_eh_region_end () is invoked.  CLEANUP is
 171    the cleanup action to perform.  The return value is true if the
 172    exception region was optimized away.  If that case,
 173    expand_eh_region_end does not need to be called for this cleanup,
 174    nor should it be.
 175
 176    This routine notices one particular common case in C++ code
 177    generation, and optimizes it so as to not need the exception
 178    region.  */
 179
 180 extern int expand_eh_region_start_tree          PARAMS ((tree, tree));
 181
 182 /* End an exception handling region.  The information about the region
 183    is found on the top of ehstack.
 184
 185    HANDLER is either the cleanup for the exception region, or if we're
 186    marking the end of a try block, HANDLER is integer_zero_node.
 187
 188    HANDLER will be transformed to rtl when expand_leftover_cleanups ()
 189    is invoked.  */
 190
 191 extern void expand_eh_region_end                PARAMS ((tree));
 192
 193 /* Push RLABEL or TLABEL onto LABELSTACK. Only one of RLABEL or TLABEL
 194    should be set; the other must be NULL.  */
 195
 196 extern void push_label_entry    PARAMS ((struct label_node **labelstack,
 197                                          rtx rlabel, tree tlabel));
 198
 199 /* Pop the topmost entry from LABELSTACK and return its value as an
 200    rtx node. If LABELSTACK is empty, return NULL.  */
 201
 202 extern rtx pop_label_entry      PARAMS ((struct label_node **labelstack));
 203
 204 /* Return the topmost entry of LABELSTACK as a tree node, or return
 205    NULL_TREE if LABELSTACK is empty.  */
 206
 207 extern tree top_label_entry     PARAMS ((struct label_node **labelstack));
 208
 209 #endif
 210
 211 /* Test: is exception handling turned on? */
 212
 213 extern int doing_eh                             PARAMS ((int));
 214
 215 /* Toplevel initialization for EH.  */
 216
 217 void set_exception_lang_code                    PARAMS ((int));
 218 void set_exception_version_code                 PARAMS ((int));
 219
 220 /* A list of handlers asocciated with an exception region. HANDLER_LABEL
 221    is the the label that control should be transfered to if the data
 222    in TYPE_INFO matches an exception. a value of NULL_TREE for TYPE_INFO
 223    means This is a cleanup, and must always be called. A value of
 224    CATCH_ALL_TYPE works like a cleanup, but a call to the runtime matcher
 225    is still performed to avoid being caught by a different language
 226    exception. NEXT is a pointer to the next handler for this region.
 227    NULL means there are no more. */
 228
 229 typedef struct handler_info
 230 {
 231   rtx handler_label;
 232   int handler_number;
 233   void *type_info;
 234   struct handler_info *next;
 235 } handler_info;
 236
 237
 238 /* Add new handler information to an exception range. The  first parameter
 239    specifies the range number (returned from new_eh_entry()). The second
 240    parameter specifies the handler.  By default the handler is inserted at
 241    the end of the list. A handler list may contain only ONE NULL_TREE
 242    typeinfo entry. Regardless where it is positioned, a NULL_TREE entry
 243    is always output as the LAST handler in the exception table for a region. */
 244
 245 void add_new_handler                    PARAMS ((int, struct handler_info *));
 246
 247 /* Remove a handler label. The handler label is being deleted, so all
 248    regions which reference this handler should have it removed from their
 249    list of possible handlers. Any region which has the final handler
 250    removed can be deleted. */
 251
 252 void remove_handler                     PARAMS ((rtx));
 253
 254 /* Create a new handler structure initialized with the handler label and
 255    typeinfo fields passed in. */
 256
 257 struct handler_info *get_new_handler            PARAMS ((rtx, void *));
 258
 259 /* Make a duplicate of an exception region by copying all the handlers
 260    for an exception region. Return the new handler index. */
 261
 262 int duplicate_eh_handlers               PARAMS ((int, int, rtx (*)(rtx)));
 263
 264 /* map symbol refs for rethrow */
 265
 266 rtx rethrow_symbol_map                          PARAMS ((rtx, rtx (*)(rtx)));
 267
 268 /* Is the rethrow label for a region used? */
 269
 270 int rethrow_used                                PARAMS ((int));
 271
 272 /* Update the rethrow references to reflect rethrows which have been
 273    optimized away.  */
 274
 275 void update_rethrow_references                  PARAMS ((void));
 276
 277 /* Get a pointer to the first handler in an exception region's list. */
 278
 279 struct handler_info *get_first_handler          PARAMS ((int));
 280
 281 /* Find all the runtime handlers type matches currently referenced */
 282
 283 int find_all_handler_type_matches               PARAMS ((void ***));
 284
 285 /* The eh_nesting_info structure is used to find a list of valid handlers
 286    for any arbitrary exception region.  When init_eh_nesting_info is called,
 287    the information is all pre-calculated and entered in this structure.
 288    REGION_INDEX is a vector over all possible region numbers.  Since the
 289    number of regions is typically much smaller than the range of block
 290    numbers, this is a sparse vector and the other data structures are
 291    represented as dense vectors.  Indexed with an exception region number, this
 292    returns the index to use in the other data structures to retreive the
 293    correct information.
 294    HANDLERS is an array of vectors which point to handler_info structures.
 295    when indexed, it gives the list of all possible handlers which can
 296    be reached by a throw from this exception region.
 297    NUM_HANDLERS is the equivilent array indicating how many handler
 298    pointers there are in the HANDLERS vector.
 299    OUTER_INDEX indicates which index represents the information for the
 300    outer block.  0 indicates there is no outer context.
 301    REGION_COUNT is the number of regions.  */
 302
 303 typedef struct eh_nesting
 304 {
 305   int *region_index;
 306   handler_info ***handlers;
 307   int *num_handlers;
 308   int *outer_index;
 309   int region_count;
 310 } eh_nesting_info;
 311
 312 /* Initialize the eh_nesting_info structure.  */
 313
 314 eh_nesting_info *init_eh_nesting_info           PARAMS ((void));
 315
 316 /* Get a list of handlers reachable from a an exception region/insn.  */
 317
 318 int reachable_handlers                  PARAMS ((int, eh_nesting_info *, rtx,
 319                                                  handler_info ***handlers));
 320
 321 /* Free the eh_nesting_info structure.  */
 322
 323 void free_eh_nesting_info                       PARAMS ((eh_nesting_info *));
 324
 325 extern void init_eh                             PARAMS ((void));
 326
 327 /* Initialization for the per-function EH data.  */
 328
 329 extern void init_eh_for_function                PARAMS ((void));
 330
 331 /* Generate an exception label. Use instead of gen_label_rtx */
 332
 333 extern rtx gen_exception_label                  PARAMS ((void));
 334
 335 /* Adds an EH table entry for EH entry number N. Called from
 336    final_scan_insn for NOTE_INSN_EH_REGION_BEG.  */
 337
 338 extern void add_eh_table_entry                  PARAMS ((int n));
 339
 340 /* Start a catch clause, triggered by runtime value paramter. */
 341
 342 #ifdef TREE_CODE
 343 extern void start_catch_handler                 PARAMS ((tree));
 344 #endif
 345
 346 /* End an individual catch clause. */
 347
 348 extern void end_catch_handler                   PARAMS ((void));
 349
 350 /* Returns a non-zero value if we need to output an exception table.  */
 351
 352 extern int exception_table_p                    PARAMS ((void));
 353
 354 /* Outputs the exception table if we have one.  */
 355
 356 extern void output_exception_table              PARAMS ((void));
 357 extern void output_exception_table_data         PARAMS ((void));
 358
 359 /* Free the exception table.  */
 360
 361 extern void free_exception_table                PARAMS((void));
 362
 363 /* Used by the ia64 unwind format to output data for an individual
 364    function.  */
 365
 366 extern void output_function_exception_table     PARAMS((void));
 367
 368 /* Given a return address in ADDR, determine the address we should use
 369    to find the corresponding EH region.  */
 370
 371 extern rtx eh_outer_context                     PARAMS ((rtx addr));
 372
 373 /* Called at the start of a block of try statements for which there is
 374    a supplied catch handler.  */
 375
 376 extern void expand_start_try_stmts              PARAMS ((void));
 377
 378 /* Called at the start of a block of catch statements. It terminates the
 379    previous set of try statements.  */
 380
 381 extern void expand_start_all_catch              PARAMS ((void));
 382
 383 /* Called at the end of a block of catch statements.  */
 384
 385 extern void expand_end_all_catch                PARAMS ((void));
 386
 387 /* Begin a region that will contain entries created with
 388    add_partial_entry.  */
 389
 390 extern void begin_protect_partials              PARAMS ((void));
 391
 392 #ifdef TREE_CODE
 393 /* Create a new exception region and add the handler for the region
 394    onto a list. These regions will be ended (and their handlers
 395    emitted) when end_protect_partials is invoked.  */
 396
 397 extern void add_partial_entry                   PARAMS ((tree handler));
 398 #endif
 399
 400 /* End all of the pending exception regions that have handlers added with
 401    push_protect_entry ().  */
 402
 403 extern void end_protect_partials                PARAMS ((void));
 404
 405 /* An internal throw.  */
 406
 407 extern void expand_internal_throw               PARAMS ((void));
 408
 409 /* Called from expand_exception_blocks and expand_end_catch_block to
 410    expand and pending handlers.  */
 411
 412 extern void expand_leftover_cleanups            PARAMS ((void));
 413
 414 /* If necessary, emit insns to get EH context for the current
 415    function. */
 416
 417 extern void emit_eh_context                     PARAMS ((void));
 418
 419 /* Builds a list of handler labels and puts them in the global
 420    variable exception_handler_labels.  */
 421
 422 extern void find_exception_handler_labels       PARAMS ((void));
 423
 424 /* Determine if an arbitrary label is an exception label */
 425
 426 extern int is_exception_handler_label           PARAMS ((int));
 427
 428 /* Performs sanity checking on the check_exception_handler_labels
 429    list.  */
 430
 431 extern void check_exception_handler_labels      PARAMS ((void));
 432
 433 /* Keeps track of the label used as the context of a throw to rethrow an
 434    exception to the outer exception region.  */
 435
 436 extern struct label_node *outer_context_label_stack;
 437
 438 /* A list of labels used for exception handlers. It is created by
 439    find_exception_handler_labels for the optimization passes.  */
 440
 441 extern rtx exception_handler_labels;
 442
 443 /* Determine if the given INSN can throw an exception.  */
 444
 445 extern int can_throw                            PARAMS ((rtx));
 446
 447 /* Return nonzero if nothing in this function can throw.  */
 448
 449 extern int nothrow_function_p                   PARAMS ((void));
 450
 451 /* Performs optimizations for exception handling, such as removing
 452    unnecessary exception regions. Invoked from jump_optimize ().  */
 453
 454 extern void exception_optimize                  PARAMS ((void));
 455
 456 /* Return EH context (and set it up once per fn).  */
 457 extern rtx get_eh_context                       PARAMS ((void));
 458
 459 /* Get the dynamic handler chain.  */
 460 extern rtx get_dynamic_handler_chain            PARAMS ((void));
 461
 462 /* Get the dynamic cleanup chain.  */
 463 extern rtx get_dynamic_cleanup_chain            PARAMS ((void));
 464
 465 /* Throw an exception.  */
 466
 467 extern void emit_throw                          PARAMS ((void));
 468
 469 /* Save away the current ehqueue.  */
 470 extern void push_ehqueue                        PARAMS ((void));
 471
 472 /* Restore a previously pushed ehqueue.  */
 473 extern void pop_ehqueue                         PARAMS ((void));
 474
 475 /* One to use setjmp/longjmp method of generating code.  */
 476
 477 extern int exceptions_via_longjmp;
 478
 479 /* One to enable asynchronous exception support.  */
 480
 481 extern int asynchronous_exceptions;
 482
 483 /* One to protect cleanup actions with a handler that calls
 484    __terminate, zero otherwise.  */
 485
 486 extern int protect_cleanup_actions_with_terminate;
 487
 488 #ifdef TREE_CODE
 489 extern tree protect_with_terminate              PARAMS ((tree));
 490 #endif
 491
 492 extern void expand_fixup_region_start   PARAMS ((void));
 493 #ifdef TREE_CODE
 494 extern void expand_fixup_region_end     PARAMS ((tree));
 495 #endif
 496
 497 /* Various hooks for the DWARF 2 __throw routine.  */
 498
 499 void expand_builtin_unwind_init         PARAMS ((void));
 500 rtx expand_builtin_dwarf_fp_regnum      PARAMS ((void));
 501 #ifdef TREE_CODE
 502 rtx expand_builtin_frob_return_addr     PARAMS ((tree));
 503 rtx expand_builtin_extract_return_addr  PARAMS ((tree));
 504 void expand_builtin_init_dwarf_reg_sizes        PARAMS ((tree));
 505 void expand_builtin_eh_return           PARAMS ((tree, tree, tree));
 506 #endif
 507 void expand_eh_return                   PARAMS ((void));
 508
 509
 510 /* Checking whether 2 instructions are within the same exception region. */
 511
 512 int in_same_eh_region                   PARAMS ((rtx, rtx));
 513 void free_insn_eh_region                PARAMS ((void));
 514 void init_insn_eh_region                PARAMS ((rtx, int));
 515
 516 #ifdef rtx
 517 #undef rtx
 518 #endif