gcc/java/except.c

   1 /* Handle exceptions for GNU compiler for the Java(TM) language.
   2    Copyright (C) 1997, 1998, 1999, 2000, 2002, 2003
   3    Free Software Foundation, Inc.
   4
   5 This file is part of GCC.
   6
   7 GCC 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 GCC 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 GCC; 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 Java and all Java-based marks are trademarks or registered trademarks
  23 of Sun Microsystems, Inc. in the United States and other countries.
  24 The Free Software Foundation is independent of Sun Microsystems, Inc.  */
  25
  26 #include "config.h"
  27 #include "system.h"
  28 #include "coretypes.h"
  29 #include "tm.h"
  30 #include "tree.h"
  31 #include "real.h"
  32 #include "rtl.h"
  33 #include "java-tree.h"
  34 #include "javaop.h"
  35 #include "java-opcodes.h"
  36 #include "jcf.h"
  37 #include "function.h"
  38 #include "except.h"
  39 #include "java-except.h"
  40 #include "toplev.h"
  41
  42 static void expand_start_java_handler (struct eh_range *);
  43 static void expand_end_java_handler (struct eh_range *);
  44 static struct eh_range *find_handler_in_range (int, struct eh_range *,
  45                                                struct eh_range *);
  46 static void link_handler (struct eh_range *, struct eh_range *);
  47 static void check_start_handlers (struct eh_range *, int);
  48 static void free_eh_ranges (struct eh_range *range);
  49
  50 struct eh_range *current_method_handlers;
  51
  52 struct eh_range *current_try_block = NULL;
  53
  54 struct eh_range *eh_range_freelist = NULL;
  55
  56 /* These variables are used to speed up find_handler. */
  57
  58 static int cache_range_start, cache_range_end;
  59 static struct eh_range *cache_range;
  60 static struct eh_range *cache_next_child;
  61
  62 /* A dummy range that represents the entire method. */
  63
  64 struct eh_range whole_range;
  65
  66 #if defined(DEBUG_JAVA_BINDING_LEVELS)
  67 extern int binding_depth;
  68 extern int is_class_level;
  69 extern int current_pc;
  70 extern void indent ();
  71
  72 #endif
  73
  74 /* Search for the most specific eh_range containing PC.
  75    Assume PC is within RANGE.
  76    CHILD is a list of children of RANGE such that any
  77    previous children have end_pc values that are too low. */
  78
  79 static struct eh_range *
  80 find_handler_in_range (int pc, struct eh_range *range, struct eh_range *child)
  81 {
  82   for (; child != NULL;  child = child->next_sibling)
  83     {
  84       if (pc < child->start_pc)
  85         break;
  86       if (pc < child->end_pc)
  87         return find_handler_in_range (pc, child, child->first_child);
  88     }
  89   cache_range = range;
  90   cache_range_start = pc;
  91   cache_next_child = child;
  92   cache_range_end = child == NULL ? range->end_pc : child->start_pc;
  93   return range;
  94 }
  95
  96 /* Find the inner-most handler that contains PC. */
  97
  98 struct eh_range *
  99 find_handler (int pc)
 100 {
 101   struct eh_range *h;
 102   if (pc >= cache_range_start)
 103     {
 104       h = cache_range;
 105       if (pc < cache_range_end)
 106         return h;
 107       while (pc >= h->end_pc)
 108         {
 109           cache_next_child = h->next_sibling;
 110           h = h->outer;
 111         }
 112     }
 113   else
 114     {
 115       h = &whole_range;
 116       cache_next_child = h->first_child;
 117     }
 118   return find_handler_in_range (pc, h, cache_next_child);
 119 }
 120
 121 /* Recursive helper routine for check_nested_ranges. */
 122
 123 static void
 124 link_handler (struct eh_range *range, struct eh_range *outer)
 125 {
 126   struct eh_range **ptr;
 127
 128   if (range->start_pc == outer->start_pc && range->end_pc == outer->end_pc)
 129     {
 130       outer->handlers = chainon (outer->handlers, range->handlers);
 131       return;
 132     }
 133
 134   /* If the new range completely encloses the `outer' range, then insert it
 135      between the outer range and its parent.  */
 136   if (range->start_pc <= outer->start_pc && range->end_pc >= outer->end_pc)
 137     {
 138       range->outer = outer->outer;
 139       range->next_sibling = NULL;
 140       range->first_child = outer;
 141       {
 142         struct eh_range **pr = &(outer->outer->first_child);
 143         while (*pr != outer)
 144           pr = &(*pr)->next_sibling;
 145         *pr = range;
 146       }
 147       outer->outer = range;
 148       return;
 149     }
 150
 151   /* Handle overlapping ranges by splitting the new range.  */
 152   if (range->start_pc < outer->start_pc || range->end_pc > outer->end_pc)
 153     {
 154       struct eh_range *h = xmalloc (sizeof (struct eh_range));
 155       if (range->start_pc < outer->start_pc)
 156         {
 157           h->start_pc = range->start_pc;
 158           h->end_pc = outer->start_pc;
 159           range->start_pc = outer->start_pc;
 160         }
 161       else
 162         {
 163           h->start_pc = outer->end_pc;
 164           h->end_pc = range->end_pc;
 165           range->end_pc = outer->end_pc;
 166         }
 167       h->first_child = NULL;
 168       h->outer = NULL;
 169       h->handlers = build_tree_list (TREE_PURPOSE (range->handlers),
 170                                      TREE_VALUE (range->handlers));
 171       h->next_sibling = NULL;
 172       h->expanded = 0;
 173       /* Restart both from the top to avoid having to make this
 174          function smart about reentrancy.  */
 175       link_handler (h, &whole_range);
 176       link_handler (range, &whole_range);
 177       return;
 178     }
 179
 180   ptr = &outer->first_child;
 181   for (;; ptr = &(*ptr)->next_sibling)
 182     {
 183       if (*ptr == NULL || range->end_pc <= (*ptr)->start_pc)
 184         {
 185           range->next_sibling = *ptr;
 186           range->first_child = NULL;
 187           range->outer = outer;
 188           *ptr = range;
 189           return;
 190         }
 191       else if (range->start_pc < (*ptr)->end_pc)
 192         {
 193           link_handler (range, *ptr);
 194           return;
 195         }
 196       /* end_pc > (*ptr)->start_pc && start_pc >= (*ptr)->end_pc. */
 197     }
 198 }
 199
 200 /* The first pass of exception range processing (calling add_handler)
 201    constructs a linked list of exception ranges.  We turn this into
 202    the data structure expected by the rest of the code, and also
 203    ensure that exception ranges are properly nested.  */
 204
 205 void
 206 handle_nested_ranges (void)
 207 {
 208   struct eh_range *ptr, *next;
 209
 210   ptr = whole_range.first_child;
 211   whole_range.first_child = NULL;
 212   for (; ptr; ptr = next)
 213     {
 214       next = ptr->next_sibling;
 215       ptr->next_sibling = NULL;
 216       link_handler (ptr, &whole_range);
 217     }
 218 }
 219
 220 /* Free RANGE as well as its children and siblings.  */
 221
 222 static void
 223 free_eh_ranges (struct eh_range *range)
 224 {
 225   while (range)
 226     {
 227       struct eh_range *next = range->next_sibling;
 228       free_eh_ranges (range->first_child);
 229       if (range != &whole_range)
 230         free (range);
 231       range = next;
 232     }
 233 }
 234
 235 /* Called to re-initialize the exception machinery for a new method. */
 236
 237 void
 238 method_init_exceptions (void)
 239 {
 240   free_eh_ranges (&whole_range);
 241   whole_range.start_pc = 0;
 242   whole_range.end_pc = DECL_CODE_LENGTH (current_function_decl) + 1;
 243   whole_range.outer = NULL;
 244   whole_range.first_child = NULL;
 245   whole_range.next_sibling = NULL;
 246   cache_range_start = 0xFFFFFF;
 247 }
 248
 249 /* Add an exception range.  If we already have an exception range
 250    which has the same handler and label, and the new range overlaps
 251    that one, then we simply extend the existing range.  Some bytecode
 252    obfuscators generate seemingly nonoverlapping exception ranges
 253    which, when coalesced, do in fact nest correctly.
 254
 255    This constructs an ordinary linked list which check_nested_ranges()
 256    later turns into the data structure we actually want.
 257
 258    We expect the input to come in order of increasing START_PC.  This
 259    function doesn't attempt to detect the case where two previously
 260    added disjoint ranges could be coalesced by a new range; that is
 261    what the sorting counteracts.  */
 262
 263 void
 264 add_handler (int start_pc, int end_pc, tree handler, tree type)
 265 {
 266   struct eh_range *ptr, *prev = NULL, *h;
 267
 268   for (ptr = whole_range.first_child; ptr; ptr = ptr->next_sibling)
 269     {
 270       if (start_pc >= ptr->start_pc
 271           && start_pc <= ptr->end_pc
 272           && TREE_PURPOSE (ptr->handlers) == type
 273           && TREE_VALUE (ptr->handlers) == handler)
 274         {
 275           /* Already found an overlapping range, so coalesce.  */
 276           ptr->end_pc = MAX (ptr->end_pc, end_pc);
 277           return;
 278         }
 279       prev = ptr;
 280     }
 281
 282   h = xmalloc (sizeof (struct eh_range));
 283   h->start_pc = start_pc;
 284   h->end_pc = end_pc;
 285   h->first_child = NULL;
 286   h->outer = NULL;
 287   h->handlers = build_tree_list (type, handler);
 288   h->next_sibling = NULL;
 289   h->expanded = 0;
 290
 291   if (prev == NULL)
 292     whole_range.first_child = h;
 293   else
 294     prev->next_sibling = h;
 295 }
 296
 297
 298 /* if there are any handlers for this range, issue start of region */
 299 static void
 300 expand_start_java_handler (struct eh_range *range)
 301 {
 302 #if defined(DEBUG_JAVA_BINDING_LEVELS)
 303   indent ();
 304   fprintf (stderr, "expand start handler pc %d --> %d\n",
 305            current_pc, range->end_pc);
 306 #endif /* defined(DEBUG_JAVA_BINDING_LEVELS) */
 307   range->expanded = 1;
 308   expand_eh_region_start ();
 309 }
 310
 311 tree
 312 prepare_eh_table_type (tree type)
 313 {
 314   tree exp;
 315
 316   /* The "type" (metch_info) in a (Java) exception table is one:
 317    * a) NULL - meaning match any type in a try-finally.
 318    * b) a pointer to a (compiled) class (low-order bit 0).
 319    * c) a pointer to the Utf8Const name of the class, plus one
 320    * (which yields a value with low-order bit 1). */
 321
 322   if (type == NULL_TREE)
 323     exp = NULL_TREE;
 324   else if (is_compiled_class (type))
 325     exp = build_class_ref (type);
 326   else
 327     exp = fold (build
 328                 (PLUS_EXPR, ptr_type_node,
 329                  build_utf8_ref (DECL_NAME (TYPE_NAME (type))),
 330                  size_one_node));
 331   return exp;
 332 }
 333
 334
 335 /* Build a reference to the jthrowable object being carried in the
 336    exception header.  */
 337
 338 tree
 339 build_exception_object_ref (tree type)
 340 {
 341   tree obj;
 342
 343   /* Java only passes object via pointer and doesn't require adjusting.
 344      The java object is immediately before the generic exception header.  */
 345   obj = build (EXC_PTR_EXPR, build_pointer_type (type));
 346   obj = build (MINUS_EXPR, TREE_TYPE (obj), obj,
 347                TYPE_SIZE_UNIT (TREE_TYPE (obj)));
 348   obj = build1 (INDIRECT_REF, type, obj);
 349
 350   return obj;
 351 }
 352
 353 /* If there are any handlers for this range, isssue end of range,
 354    and then all handler blocks */
 355 static void
 356 expand_end_java_handler (struct eh_range *range)
 357 {
 358   tree handler = range->handlers;
 359   force_poplevels (range->start_pc);
 360   expand_start_all_catch ();
 361   for ( ; handler != NULL_TREE; handler = TREE_CHAIN (handler))
 362     {
 363       /* For bytecode we treat exceptions a little unusually.  A
 364          `finally' clause looks like an ordinary exception handler for
 365          Throwable.  The reason for this is that the bytecode has
 366          already expanded the finally logic, and we would have to do
 367          extra (and difficult) work to get this to look like a
 368          gcc-style finally clause.  */
 369       tree type = TREE_PURPOSE (handler);
 370       if (type == NULL)
 371         type = throwable_type_node;
 372
 373       expand_start_catch (type);
 374       expand_goto (TREE_VALUE (handler));
 375       expand_end_catch ();
 376     }
 377   expand_end_all_catch ();
 378 #if defined(DEBUG_JAVA_BINDING_LEVELS)
 379   indent ();
 380   fprintf (stderr, "expand end handler pc %d <-- %d\n",
 381            current_pc, range->start_pc);
 382 #endif /* defined(DEBUG_JAVA_BINDING_LEVELS) */
 383 }
 384
 385 /* Recursive helper routine for maybe_start_handlers. */
 386
 387 static void
 388 check_start_handlers (struct eh_range *range, int pc)
 389 {
 390   if (range != NULL_EH_RANGE && range->start_pc == pc)
 391     {
 392       check_start_handlers (range->outer, pc);
 393       if (!range->expanded)
 394         expand_start_java_handler (range);
 395     }
 396 }
 397
 398
 399 static struct eh_range *current_range;
 400
 401 /* Emit any start-of-try-range starting at start_pc and ending after
 402    end_pc. */
 403
 404 void
 405 maybe_start_try (int start_pc, int end_pc)
 406 {
 407   struct eh_range *range;
 408   if (! doing_eh (1))
 409     return;
 410
 411   range = find_handler (start_pc);
 412   while (range != NULL_EH_RANGE && range->start_pc == start_pc
 413          && range->end_pc < end_pc)
 414     range = range->outer;
 415
 416   current_range = range;
 417   check_start_handlers (range, start_pc);
 418 }
 419
 420 /* Emit any end-of-try-range ending at end_pc and starting before
 421    start_pc. */
 422
 423 void
 424 maybe_end_try (int start_pc, int end_pc)
 425 {
 426   if (! doing_eh (1))
 427     return;
 428
 429   while (current_range != NULL_EH_RANGE && current_range->end_pc <= end_pc
 430          && current_range->start_pc >= start_pc)
 431     {
 432       expand_end_java_handler (current_range);
 433       current_range = current_range->outer;
 434     }
 435 }