gcc/except.h

   1 /* Exception Handling interface routines.
   2    Copyright (C) 1996-2024 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
  27
  28 struct function;
  29 struct eh_region_d;
  30
  31 /* The type of an exception region.  */
  32 enum eh_region_type
  33 {
  34   /* CLEANUP regions implement e.g. destructors run when exiting a block.
  35      They can be generated from both GIMPLE_TRY_FINALLY and GIMPLE_TRY_CATCH
  36      nodes.  It is expected by the runtime that cleanup regions will *not*
  37      resume normal program flow, but will continue propagation of the
  38      exception.  */
  39   ERT_CLEANUP,
  40
  41   /* TRY regions implement catching an exception.  The list of types associated
  42      with the attached catch handlers is examined in order by the runtime and
  43      control is transferred to the appropriate handler.  Note that a NULL type
  44      list is a catch-all handler, and that it will catch *all* exceptions
  45      including those originating from a different language.  */
  46   ERT_TRY,
  47
  48   /* ALLOWED_EXCEPTIONS regions implement exception filtering, e.g. the
  49      throw(type-list) specification that can be added to C++ functions.
  50      The runtime examines the thrown exception vs the type list, and if
  51      the exception does not match, transfers control to the handler.  The
  52      normal handler for C++ calls __cxa_call_unexpected.  */
  53   ERT_ALLOWED_EXCEPTIONS,
  54
  55   /* MUST_NOT_THROW regions prevent all exceptions from propagating.  This
  56      region type is used in C++ to surround destructors being run inside a
  57      CLEANUP region.  This differs from an ALLOWED_EXCEPTIONS region with
  58      an empty type list in that the runtime is prepared to terminate the
  59      program directly.  We only generate code for MUST_NOT_THROW regions
  60      along control paths that are already handling an exception within the
  61      current function.  */
  62   ERT_MUST_NOT_THROW
  63 };
  64
  65
  66 /* A landing pad for a given exception region.  Any transfer of control
  67    from the EH runtime to the function happens at a landing pad.  */
  68
  69 struct GTY((chain_next("%h.next_lp"))) eh_landing_pad_d
  70 {
  71   /* The linked list of all landing pads associated with the region.  */
  72   struct eh_landing_pad_d *next_lp;
  73
  74   /* The region with which this landing pad is associated.  */
  75   struct eh_region_d *region;
  76
  77   /* At the gimple level, the location to which control will be transferred
  78      for this landing pad.  There can be both EH and normal edges into the
  79      block containing the post-landing-pad label.  */
  80   tree post_landing_pad;
  81
  82   /* At the rtl level, the location to which the runtime will transfer
  83      control.  This differs from the post-landing-pad in that the target's
  84      EXCEPTION_RECEIVER pattern will be expanded here, as well as other
  85      bookkeeping specific to exceptions.  There must not be normal edges
  86      into the block containing the landing-pad label.  */
  87   rtx_code_label *landing_pad;
  88
  89   /* The index of this landing pad within fun->eh->lp_array.  */
  90   int index;
  91 };
  92
  93 /* A catch handler associated with an ERT_TRY region.  */
  94
  95 struct GTY(()) eh_catch_d
  96 {
  97   /* The double-linked list of all catch handlers for the region.  */
  98   struct eh_catch_d *next_catch;
  99   struct eh_catch_d *prev_catch;
 100
 101   /* A TREE_LIST of runtime type objects that this catch handler
 102      will catch, or NULL if all exceptions are caught.  */
 103   tree type_list;
 104
 105   /* A TREE_LIST of INTEGER_CSTs that correspond to the type_list entries,
 106      having been mapped by assign_filter_values.  These integers are to be
 107      compared against the __builtin_eh_filter value.  */
 108   tree filter_list;
 109
 110   /* The code that should be executed if this catch handler matches the
 111      thrown exception.  This label is only maintained until
 112      pass_lower_eh_dispatch, at which point it is cleared.  */
 113   tree label;
 114 };
 115
 116 /* Describes one exception region.  */
 117
 118 struct GTY(()) eh_region_d
 119 {
 120   /* The immediately surrounding region.  */
 121   struct eh_region_d *outer;
 122
 123   /* The list of immediately contained regions.  */
 124   struct eh_region_d *inner;
 125   struct eh_region_d *next_peer;
 126
 127   /* The index of this region within fun->eh->region_array.  */
 128   int index;
 129
 130   /* Each region does exactly one thing.  */
 131   enum eh_region_type type;
 132
 133   /* Holds the action to perform based on the preceding type.  */
 134   union eh_region_u {
 135     struct eh_region_u_try {
 136       /* The double-linked list of all catch handlers for this region.  */
 137       struct eh_catch_d *first_catch;
 138       struct eh_catch_d *last_catch;
 139     } GTY ((tag ("ERT_TRY"))) eh_try;
 140
 141     struct eh_region_u_allowed {
 142       /* A TREE_LIST of runtime type objects allowed to pass.  */
 143       tree type_list;
 144       /* The code that should be executed if the thrown exception does
 145          not match the type list.  This label is only maintained until
 146          pass_lower_eh_dispatch, at which point it is cleared.  */
 147       tree label;
 148       /* The integer that will be passed by the runtime to signal that
 149          we should execute the code at LABEL.  This integer is assigned
 150          by assign_filter_values and is to be compared against the
 151          __builtin_eh_filter value.  */
 152       int filter;
 153     } GTY ((tag ("ERT_ALLOWED_EXCEPTIONS"))) allowed;
 154
 155     struct eh_region_u_must_not_throw {
 156       /* A function decl to be invoked if this region is actually reachable
 157          from within the function, rather than implementable from the runtime.
 158          The normal way for this to happen is for there to be a TRY region
 159          contained within this MUST_NOT_THROW region.  Note that if the
 160          runtime handles the MUST_NOT_THROW region, we have no control over
 161          what termination function is called; it will be decided by the
 162          personality function in effect for this CIE.  */
 163       tree failure_decl;
 164       /* The location assigned to the call of FAILURE_DECL, if expanded.  */
 165       location_t failure_loc;
 166     } GTY ((tag ("ERT_MUST_NOT_THROW"))) must_not_throw;
 167   } GTY ((desc ("%0.type"))) u;
 168
 169   /* The list of landing pads associated with this region.  */
 170   struct eh_landing_pad_d *landing_pads;
 171
 172   /* EXC_PTR and FILTER values copied from the runtime for this region.
 173      Each region gets its own psuedos so that if there are nested exceptions
 174      we do not overwrite the values of the first exception.  */
 175   rtx exc_ptr_reg, filter_reg;
 176
 177   /* True if this region should use __cxa_end_cleanup instead
 178      of _Unwind_Resume.  */
 179   bool use_cxa_end_cleanup;
 180 };
 181
 182 typedef struct eh_landing_pad_d *eh_landing_pad;
 183 typedef struct eh_catch_d *eh_catch;
 184 typedef struct eh_region_d *eh_region;
 185
 186
 187
 188
 189 /* The exception status for each function.  */
 190
 191 struct GTY(()) eh_status
 192 {
 193   /* The tree of all regions for this function.  */
 194   eh_region region_tree;
 195
 196   /* The same information as an indexable array.  */
 197   vec<eh_region, va_gc> *region_array;
 198
 199   /* The landing pads as an indexable array.  */
 200   vec<eh_landing_pad, va_gc> *lp_array;
 201
 202   /* At the gimple level, a mapping from gimple statement to landing pad
 203      or must-not-throw region.  See record_stmt_eh_region.  */
 204   hash_map<gimple *, int> *GTY(()) throw_stmt_table;
 205
 206   /* All of the runtime type data used by the function.  These objects
 207      are emitted to the lang-specific-data-area for the function.  */
 208   vec<tree, va_gc> *ttype_data;
 209
 210   /* The table of all action chains.  These encode the eh_region tree in
 211      a compact form for use by the runtime, and is also emitted to the
 212      lang-specific-data-area.  Note that the ARM EABI uses a different
 213      format for the encoding than all other ports.  */
 214   union eh_status_u {
 215     vec<tree, va_gc> *GTY((tag ("1"))) arm_eabi;
 216     vec<uchar, va_gc> *GTY((tag ("0"))) other;
 217   } GTY ((desc ("targetm.arm_eabi_unwinder"))) ehspec_data;
 218 };
 219
 220
 221 /* Invokes CALLBACK for every exception handler label.  Only used by old
 222    loop hackery; should not be used by new code.  */
 223 extern void for_each_eh_label (void (*) (rtx));
 224
 225 extern void init_eh_for_function (void);
 226
 227 extern void remove_eh_landing_pad (eh_landing_pad);
 228 extern void remove_eh_handler (eh_region);
 229 extern void remove_unreachable_eh_regions (sbitmap);
 230
 231 extern bool current_function_has_exception_handlers (void);
 232 extern void output_function_exception_table (int);
 233
 234 extern rtx expand_builtin_eh_pointer (tree);
 235 extern rtx expand_builtin_eh_filter (tree);
 236 extern rtx expand_builtin_eh_copy_values (tree);
 237 extern void expand_builtin_unwind_init (void);
 238 extern rtx expand_builtin_eh_return_data_regno (tree);
 239 extern rtx expand_builtin_extract_return_addr (tree);
 240 extern void expand_builtin_init_dwarf_reg_sizes (tree);
 241 extern rtx expand_builtin_frob_return_addr (tree);
 242 extern rtx expand_builtin_dwarf_sp_column (void);
 243 extern void expand_builtin_eh_return (tree, tree);
 244 extern void expand_eh_return (void);
 245 extern rtx expand_builtin_extend_pointer (tree);
 246
 247 typedef tree (*duplicate_eh_regions_map) (tree, void *);
 248 extern hash_map<void *, void *> *duplicate_eh_regions
 249   (struct function *, eh_region, int, duplicate_eh_regions_map, void *);
 250
 251 extern void sjlj_emit_function_exit_after (rtx_insn *);
 252 extern void update_sjlj_context (void);
 253
 254 extern eh_region gen_eh_region_cleanup (eh_region);
 255 extern eh_region gen_eh_region_try (eh_region);
 256 extern eh_region gen_eh_region_allowed (eh_region, tree);
 257 extern eh_region gen_eh_region_must_not_throw (eh_region);
 258
 259 extern eh_catch gen_eh_region_catch (eh_region, tree);
 260 extern eh_landing_pad gen_eh_landing_pad (eh_region);
 261
 262 extern eh_region get_eh_region_from_number_fn (struct function *, int);
 263 extern eh_region get_eh_region_from_number (int);
 264 extern eh_landing_pad get_eh_landing_pad_from_number_fn (struct function*,int);
 265 extern eh_landing_pad get_eh_landing_pad_from_number (int);
 266 extern eh_region get_eh_region_from_lp_number_fn (struct function *, int);
 267 extern eh_region get_eh_region_from_lp_number (int);
 268
 269 extern eh_region eh_region_outermost (struct function *, eh_region, eh_region);
 270
 271 extern void make_reg_eh_region_note (rtx_insn *insn, int ecf_flags, int lp_nr);
 272 extern void make_reg_eh_region_note_nothrow_nononlocal (rtx_insn *);
 273
 274 extern void verify_eh_tree (struct function *);
 275 extern void dump_eh_tree (FILE *, struct function *);
 276 void debug_eh_tree (struct function *);
 277 extern void add_type_for_runtime (tree);
 278 extern tree lookup_type_for_runtime (tree);
 279 extern void assign_filter_values (void);
 280
 281 extern eh_region get_eh_region_from_rtx (const_rtx);
 282 extern eh_landing_pad get_eh_landing_pad_from_rtx (const_rtx);
 283
 284 extern void finish_eh_generation (void);
 285
 286 struct GTY(()) throw_stmt_node {
 287   gimple *stmt;
 288   int lp_nr;
 289 };
 290
 291 extern hash_map<gimple *, int> *get_eh_throw_stmt_table (struct function *);
 292 extern void set_eh_throw_stmt_table (function *, hash_map<gimple *, int> *);
 293
 294 enum eh_personality_kind {
 295   eh_personality_none,
 296   eh_personality_any,
 297   eh_personality_lang
 298 };
 299
 300 extern enum eh_personality_kind
 301 function_needs_eh_personality (struct function *);
 302
 303 /* Pre-order iteration within the eh_region tree.  */
 304
 305 inline eh_region
 306 ehr_next (eh_region r, eh_region start)
 307 {
 308   if (r->inner)
 309     r = r->inner;
 310   else if (r->next_peer && r != start)
 311     r = r->next_peer;
 312   else
 313     {
 314       do
 315         {
 316           r = r->outer;
 317           if (r == start)
 318             return NULL;
 319         }
 320       while (r->next_peer == NULL);
 321       r = r->next_peer;
 322     }
 323   return r;
 324 }
 325
 326 #define FOR_ALL_EH_REGION_AT(R, START) \
 327   for ((R) = (START); (R) != NULL; (R) = ehr_next (R, START))
 328
 329 #define FOR_ALL_EH_REGION_FN(R, FN) \
 330   for ((R) = (FN)->eh->region_tree; (R) != NULL; (R) = ehr_next (R, NULL))
 331
 332 #define FOR_ALL_EH_REGION(R) FOR_ALL_EH_REGION_FN (R, cfun)
 333
 334 #endif