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   /* A random data area for the front end's own use.  */
 124   struct label_node *x_false_label_stack;
 125   /* Keeps track of the label to resume to should one want to resume
 126      normal control flow out of a handler (instead of, say, returning to
 127      the caller of the current function or exiting the program).  */
 128   struct label_node *x_caught_return_label_stack;
 129   /* A stack (TREE_LIST) of lists of handlers.  The TREE_VALUE of each
 130      node is itself a TREE_CHAINed list of handlers for regions that
 131      are not yet closed. The TREE_VALUE of each entry contains the
 132      handler for the corresponding entry on the ehstack.  */
 133   union tree_node *x_protect_list;
 134   /* The EH context.  Nonzero if the function has already
 135      fetched a pointer to the EH context  for exception handling.  */
 136   rtx ehc;
 137   /* The label generated by expand_builtin_eh_return.  */
 138   rtx x_eh_return_stub_label;
 139 };
 140
 141 #define ehstack (cfun->eh->x_ehstack)
 142 #define catchstack (cfun->eh->x_catchstack)
 143 #define ehqueue (cfun->eh->x_ehqueue)
 144 #define catch_clauses (cfun->eh->x_catch_clauses)
 145 #define false_label_stack (cfun->eh->x_false_label_stack)
 146 #define caught_return_label_stack (cfun->eh->x_caught_return_label_stack)
 147 #define protect_list (cfun->eh->x_protect_list)
 148 #define current_function_ehc (cfun->eh->ehc)
 149 #define eh_return_stub_label (cfun->eh->x_eh_return_stub_label)
 150
 151 #ifdef TREE_CODE
 152 /* Start an exception handling region.  All instructions emitted after
 153    this point are considered to be part of the region until
 154    expand_eh_region_end () is invoked.  */
 155
 156 extern void expand_eh_region_start              PARAMS ((void));
 157
 158 /* Just like expand_eh_region_start, except if a cleanup action is
 159    entered on the cleanup chain, the TREE_PURPOSE of the element put
 160    on the chain is DECL.  DECL should be the associated VAR_DECL, if
 161    any, otherwise it should be NULL_TREE.  */
 162
 163 extern void expand_eh_region_start_for_decl     PARAMS ((tree));
 164
 165 /* Start an exception handling region for the given cleanup action.
 166    All instructions emitted after this point are considered to be part
 167    of the region until expand_eh_region_end () is invoked.  CLEANUP is
 168    the cleanup action to perform.  The return value is true if the
 169    exception region was optimized away.  If that case,
 170    expand_eh_region_end does not need to be called for this cleanup,
 171    nor should it be.
 172
 173    This routine notices one particular common case in C++ code
 174    generation, and optimizes it so as to not need the exception
 175    region.  */
 176
 177 extern int expand_eh_region_start_tree          PARAMS ((tree, tree));
 178
 179 /* End an exception handling region.  The information about the region
 180    is found on the top of ehstack.
 181
 182    HANDLER is either the cleanup for the exception region, or if we're
 183    marking the end of a try block, HANDLER is integer_zero_node.
 184
 185    HANDLER will be transformed to rtl when expand_leftover_cleanups ()
 186    is invoked.  */
 187
 188 extern void expand_eh_region_end                PARAMS ((tree));
 189
 190 /* Push RLABEL or TLABEL onto LABELSTACK. Only one of RLABEL or TLABEL
 191    should be set; the other must be NULL.  */
 192
 193 extern void push_label_entry    PARAMS ((struct label_node **labelstack,
 194                                          rtx rlabel, tree tlabel));
 195
 196 /* Pop the topmost entry from LABELSTACK and return its value as an
 197    rtx node. If LABELSTACK is empty, return NULL.  */
 198
 199 extern rtx pop_label_entry      PARAMS ((struct label_node **labelstack));
 200
 201 /* Return the topmost entry of LABELSTACK as a tree node, or return
 202    NULL_TREE if LABELSTACK is empty.  */
 203
 204 extern tree top_label_entry     PARAMS ((struct label_node **labelstack));
 205
 206 #endif
 207
 208 /* Test: is exception handling turned on? */
 209
 210 extern int doing_eh                             PARAMS ((int));
 211
 212 /* Toplevel initialization for EH.  */
 213
 214 void set_exception_lang_code                    PARAMS ((int));
 215 void set_exception_version_code                 PARAMS ((int));
 216
 217 /* A list of handlers asocciated with an exception region. HANDLER_LABEL
 218    is the the label that control should be transfered to if the data
 219    in TYPE_INFO matches an exception. a value of NULL_TREE for TYPE_INFO
 220    means This is a cleanup, and must always be called. A value of
 221    CATCH_ALL_TYPE works like a cleanup, but a call to the runtime matcher
 222    is still performed to avoid being caught by a different language
 223    exception. NEXT is a pointer to the next handler for this region.
 224    NULL means there are no more. */
 225
 226 typedef struct handler_info
 227 {
 228   rtx handler_label;
 229   int handler_number;
 230   void *type_info;
 231   struct handler_info *next;
 232 } handler_info;
 233
 234
 235 /* Add new handler information to an exception range. The  first parameter
 236    specifies the range number (returned from new_eh_entry()). The second
 237    parameter specifies the handler.  By default the handler is inserted at
 238    the end of the list. A handler list may contain only ONE NULL_TREE
 239    typeinfo entry. Regardless where it is positioned, a NULL_TREE entry
 240    is always output as the LAST handler in the exception table for a region. */
 241
 242 void add_new_handler                    PARAMS ((int, struct handler_info *));
 243
 244 /* Remove a handler label. The handler label is being deleted, so all
 245    regions which reference this handler should have it removed from their
 246    list of possible handlers. Any region which has the final handler
 247    removed can be deleted. */
 248
 249 void remove_handler                     PARAMS ((rtx));
 250
 251 /* Create a new handler structure initialized with the handler label and
 252    typeinfo fields passed in. */
 253
 254 struct handler_info *get_new_handler            PARAMS ((rtx, void *));
 255
 256 /* Make a duplicate of an exception region by copying all the handlers
 257    for an exception region. Return the new handler index. */
 258
 259 int duplicate_eh_handlers               PARAMS ((int, int, rtx (*)(rtx)));
 260
 261 /* map symbol refs for rethrow */
 262
 263 rtx rethrow_symbol_map                          PARAMS ((rtx, rtx (*)(rtx)));
 264
 265 /* Is the rethrow label for a region used? */
 266
 267 int rethrow_used                                PARAMS ((int));
 268
 269 /* Update the rethrow references to reflect rethrows which have been
 270    optimized away.  */
 271
 272 void update_rethrow_references                  PARAMS ((void));
 273
 274 /* Get a pointer to the first handler in an exception region's list. */
 275
 276 struct handler_info *get_first_handler          PARAMS ((int));
 277
 278 /* Find all the runtime handlers type matches currently referenced */
 279
 280 int find_all_handler_type_matches               PARAMS ((void ***));
 281
 282 /* The eh_nesting_info structure is used to find a list of valid handlers
 283    for any arbitrary exception region.  When init_eh_nesting_info is called,
 284    the information is all pre-calculated and entered in this structure.
 285    REGION_INDEX is a vector over all possible region numbers.  Since the
 286    number of regions is typically much smaller than the range of block
 287    numbers, this is a sparse vector and the other data structures are
 288    represented as dense vectors.  Indexed with an exception region number, this
 289    returns the index to use in the other data structures to retreive the
 290    correct information.
 291    HANDLERS is an array of vectors which point to handler_info structures.
 292    when indexed, it gives the list of all possible handlers which can
 293    be reached by a throw from this exception region.
 294    NUM_HANDLERS is the equivilent array indicating how many handler
 295    pointers there are in the HANDLERS vector.
 296    OUTER_INDEX indicates which index represents the information for the
 297    outer block.  0 indicates there is no outer context.
 298    REGION_COUNT is the number of regions.  */
 299
 300 typedef struct eh_nesting
 301 {
 302   int *region_index;
 303   handler_info ***handlers;
 304   int *num_handlers;
 305   int *outer_index;
 306   int region_count;
 307 } eh_nesting_info;
 308
 309 /* Initialize the eh_nesting_info structure.  */
 310
 311 eh_nesting_info *init_eh_nesting_info           PARAMS ((void));
 312
 313 /* Get a list of handlers reachable from a an exception region/insn.  */
 314
 315 int reachable_handlers                  PARAMS ((int, eh_nesting_info *, rtx,
 316                                                  handler_info ***handlers));
 317
 318 /* Free the eh_nesting_info structure.  */
 319
 320 void free_eh_nesting_info                       PARAMS ((eh_nesting_info *));
 321
 322 extern void init_eh                             PARAMS ((void));
 323
 324 /* Initialization for the per-function EH data.  */
 325
 326 extern void init_eh_for_function                PARAMS ((void));
 327
 328 /* Generate an exception label. Use instead of gen_label_rtx */
 329
 330 extern rtx gen_exception_label                  PARAMS ((void));
 331
 332 /* Adds an EH table entry for EH entry number N. Called from
 333    final_scan_insn for NOTE_INSN_EH_REGION_BEG.  */
 334
 335 extern void add_eh_table_entry                  PARAMS ((int n));
 336
 337 /* Start a catch clause, triggered by runtime value paramter. */
 338
 339 #ifdef TREE_CODE
 340 extern void start_catch_handler                 PARAMS ((tree));
 341 #endif
 342
 343 /* End an individual catch clause. */
 344
 345 extern void end_catch_handler                   PARAMS ((void));
 346
 347 /* Returns a non-zero value if we need to output an exception table.  */
 348
 349 extern int exception_table_p                    PARAMS ((void));
 350
 351 /* Outputs the exception table if we have one.  */
 352
 353 extern void output_exception_table              PARAMS ((void));
 354
 355 /* Given a return address in ADDR, determine the address we should use
 356    to find the corresponding EH region.  */
 357
 358 extern rtx eh_outer_context                     PARAMS ((rtx addr));
 359
 360 /* Called at the start of a block of try statements for which there is
 361    a supplied catch handler.  */
 362
 363 extern void expand_start_try_stmts              PARAMS ((void));
 364
 365 /* Called at the start of a block of catch statements. It terminates the
 366    previous set of try statements.  */
 367
 368 extern void expand_start_all_catch              PARAMS ((void));
 369
 370 /* Called at the end of a block of catch statements.  */
 371
 372 extern void expand_end_all_catch                PARAMS ((void));
 373
 374 /* Begin a region that will contain entries created with
 375    add_partial_entry.  */
 376
 377 extern void begin_protect_partials              PARAMS ((void));
 378
 379 #ifdef TREE_CODE
 380 /* Create a new exception region and add the handler for the region
 381    onto a list. These regions will be ended (and their handlers
 382    emitted) when end_protect_partials is invoked.  */
 383
 384 extern void add_partial_entry                   PARAMS ((tree handler));
 385 #endif
 386
 387 /* End all of the pending exception regions that have handlers added with
 388    push_protect_entry ().  */
 389
 390 extern void end_protect_partials                PARAMS ((void));
 391
 392 /* An internal throw.  */
 393
 394 extern void expand_internal_throw               PARAMS ((void));
 395
 396 /* Called from expand_exception_blocks and expand_end_catch_block to
 397    expand and pending handlers.  */
 398
 399 extern void expand_leftover_cleanups            PARAMS ((void));
 400
 401 /* If necessary, emit insns to get EH context for the current
 402    function. */
 403
 404 extern void emit_eh_context                     PARAMS ((void));
 405
 406 /* Builds a list of handler labels and puts them in the global
 407    variable exception_handler_labels.  */
 408
 409 extern void find_exception_handler_labels       PARAMS ((void));
 410
 411 /* Determine if an arbitrary label is an exception label */
 412
 413 extern int is_exception_handler_label           PARAMS ((int));
 414
 415 /* Performs sanity checking on the check_exception_handler_labels
 416    list.  */
 417
 418 extern void check_exception_handler_labels      PARAMS ((void));
 419
 420 /* Keeps track of the label used as the context of a throw to rethrow an
 421    exception to the outer exception region.  */
 422
 423 extern struct label_node *outer_context_label_stack;
 424
 425 /* A list of labels used for exception handlers. It is created by
 426    find_exception_handler_labels for the optimization passes.  */
 427
 428 extern rtx exception_handler_labels;
 429
 430 /* Return nonzero if nothing in this function can throw.  */
 431
 432 extern int nothrow_function_p                   PARAMS ((void));
 433
 434 /* Performs optimizations for exception handling, such as removing
 435    unnecessary exception regions. Invoked from jump_optimize ().  */
 436
 437 extern void exception_optimize                  PARAMS ((void));
 438
 439 /* Return EH context (and set it up once per fn).  */
 440 extern rtx get_eh_context                       PARAMS ((void));
 441
 442 /* Get the dynamic handler chain.  */
 443 extern rtx get_dynamic_handler_chain            PARAMS ((void));
 444
 445 /* Get the dynamic cleanup chain.  */
 446 extern rtx get_dynamic_cleanup_chain            PARAMS ((void));
 447
 448 /* Throw an exception.  */
 449
 450 extern void emit_throw                          PARAMS ((void));
 451
 452 /* Save away the current ehqueue.  */
 453 extern void push_ehqueue                        PARAMS ((void));
 454
 455 /* Restore a previously pushed ehqueue.  */
 456 extern void pop_ehqueue                         PARAMS ((void));
 457
 458 /* One to use setjmp/longjmp method of generating code.  */
 459
 460 extern int exceptions_via_longjmp;
 461
 462 /* One to enable asynchronous exception support.  */
 463
 464 extern int asynchronous_exceptions;
 465
 466 /* One to protect cleanup actions with a handler that calls
 467    __terminate, zero otherwise.  */
 468
 469 extern int protect_cleanup_actions_with_terminate;
 470
 471 #ifdef TREE_CODE
 472 extern tree protect_with_terminate              PARAMS ((tree));
 473 #endif
 474
 475 extern void expand_fixup_region_start   PARAMS ((void));
 476 #ifdef TREE_CODE
 477 extern void expand_fixup_region_end     PARAMS ((tree));
 478 #endif
 479
 480 /* Various hooks for the DWARF 2 __throw routine.  */
 481
 482 void expand_builtin_unwind_init         PARAMS ((void));
 483 rtx expand_builtin_dwarf_fp_regnum      PARAMS ((void));
 484 #ifdef TREE_CODE
 485 rtx expand_builtin_frob_return_addr     PARAMS ((tree));
 486 rtx expand_builtin_extract_return_addr  PARAMS ((tree));
 487 void expand_builtin_init_dwarf_reg_sizes        PARAMS ((tree));
 488 void expand_builtin_eh_return           PARAMS ((tree, tree, tree));
 489 #endif
 490 void expand_eh_return                   PARAMS ((void));
 491
 492
 493 /* Checking whether 2 instructions are within the same exception region. */
 494
 495 int in_same_eh_region                   PARAMS ((rtx, rtx));
 496 void free_insn_eh_region                PARAMS ((void));
 497 void init_insn_eh_region                PARAMS ((rtx, int));
 498
 499 #ifdef rtx
 500 #undef rtx
 501 #endif