gdb/exceptions.c

   1 /* Exception (throw catch) mechanism, for GDB, the GNU debugger.
   2
   3    Copyright 1986, 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995,
   4    1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005 Free
   5    Software Foundation, Inc.
   6
   7    This file is part of GDB.
   8
   9    This program is free software; you can redistribute it and/or modify
  10    it under the terms of the GNU General Public License as published by
  11    the Free Software Foundation; either version 2 of the License, or
  12    (at your option) any later version.
  13
  14    This program is distributed in the hope that it will be useful,
  15    but WITHOUT ANY WARRANTY; without even the implied warranty of
  16    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  17    GNU General Public License for more details.
  18
  19    You should have received a copy of the GNU General Public License
  20    along with this program; if not, write to the Free Software
  21    Foundation, Inc., 59 Temple Place - Suite 330,
  22    Boston, MA 02111-1307, USA.  */
  23
  24 #include "defs.h"
  25 #include "exceptions.h"
  26 #include <setjmp.h>
  27 #include "breakpoint.h"
  28 #include "target.h"
  29 #include "inferior.h"
  30 #include "annotate.h"
  31 #include "ui-out.h"
  32 #include "gdb_assert.h"
  33 #include "gdb_string.h"
  34
  35 const struct exception exception_none = { 0, NO_ERROR, NULL };
  36
  37 /* One should use catch_errors rather than manipulating these
  38    directly.  */
  39 #if defined(HAVE_SIGSETJMP)
  40 #define SIGJMP_BUF              sigjmp_buf
  41 #define SIGSETJMP(buf)          sigsetjmp((buf), 1)
  42 #define SIGLONGJMP(buf,val)     siglongjmp((buf), (val))
  43 #else
  44 #define SIGJMP_BUF              jmp_buf
  45 #define SIGSETJMP(buf)          setjmp(buf)
  46 #define SIGLONGJMP(buf,val)     longjmp((buf), (val))
  47 #endif
  48
  49 /* Possible catcher states.  */
  50 enum catcher_state {
  51   /* Initial state, a new catcher has just been created.  */
  52   CATCHER_CREATED,
  53   /* The catch code is running.  */
  54   CATCHER_RUNNING,
  55   CATCHER_RUNNING_1,
  56   /* The catch code threw an exception.  */
  57   CATCHER_ABORTING
  58 };
  59
  60 /* Possible catcher actions.  */
  61 enum catcher_action {
  62   CATCH_ITER,
  63   CATCH_ITER_1,
  64   CATCH_THROWING
  65 };
  66
  67 struct catcher
  68 {
  69   enum catcher_state state;
  70   /* Jump buffer pointing back at the exception handler.  */
  71   SIGJMP_BUF buf;
  72   /* Status buffer belonging to the exception handler.  */
  73   volatile struct exception *exception;
  74   /* Should the error / quit message be printed?  Old code assumes
  75      that this file prints the error/quit message when first reported.
  76      New code instead directly handles the printing of error/quit
  77      messages.  */
  78   int print_message;
  79   /* Saved/current state.  */
  80   int mask;
  81   char *saved_error_pre_print;
  82   char *saved_quit_pre_print;
  83   struct ui_out *saved_uiout;
  84   struct cleanup *saved_cleanup_chain;
  85   /* Back link.  */
  86   struct catcher *prev;
  87 };
  88
  89 /* Where to go for throw_exception().  */
  90 static struct catcher *current_catcher;
  91
  92 static SIGJMP_BUF *
  93 catcher_init (struct ui_out *func_uiout,
  94               char *errstring,
  95               volatile struct exception *exception,
  96               return_mask mask,
  97               int print_message)
  98 {
  99   struct catcher *new_catcher = XZALLOC (struct catcher);
 100
 101   /* Start with no exception, save it's address.  */
 102   exception->reason = 0;
 103   exception->error = NO_ERROR;
 104   exception->message = NULL;
 105   new_catcher->exception = exception;
 106
 107   new_catcher->mask = mask;
 108   new_catcher->print_message = print_message;
 109
 110   /* Override error/quit messages during FUNC. */
 111   new_catcher->saved_error_pre_print = error_pre_print;
 112   new_catcher->saved_quit_pre_print = quit_pre_print;
 113   if (mask & RETURN_MASK_ERROR)
 114     error_pre_print = errstring;
 115   if (mask & RETURN_MASK_QUIT)
 116     quit_pre_print = errstring;
 117
 118   /* Override the global ``struct ui_out'' builder.  */
 119   new_catcher->saved_uiout = uiout;
 120   uiout = func_uiout;
 121
 122   /* Prevent error/quit during FUNC from calling cleanups established
 123      prior to here. */
 124   new_catcher->saved_cleanup_chain = save_cleanups ();
 125
 126   /* Push this new catcher on the top.  */
 127   new_catcher->prev = current_catcher;
 128   current_catcher = new_catcher;
 129   new_catcher->state = CATCHER_CREATED;
 130
 131   return &new_catcher->buf;
 132 }
 133
 134 static void
 135 catcher_pop (void)
 136 {
 137   struct catcher *old_catcher = current_catcher;
 138   current_catcher = old_catcher->prev;
 139
 140   /* Restore the cleanup chain, the error/quit messages, and the uiout
 141      builder, to their original states. */
 142
 143   restore_cleanups (old_catcher->saved_cleanup_chain);
 144
 145   uiout = old_catcher->saved_uiout;
 146
 147   quit_pre_print = old_catcher->saved_quit_pre_print;
 148   error_pre_print = old_catcher->saved_error_pre_print;
 149
 150   xfree (old_catcher);
 151 }
 152
 153 /* Catcher state machine.  Returns non-zero if the m/c should be run
 154    again, zero if it should abort.  */
 155
 156 int
 157 catcher_state_machine (enum catcher_action action)
 158 {
 159   switch (current_catcher->state)
 160     {
 161     case CATCHER_CREATED:
 162       switch (action)
 163         {
 164         case CATCH_ITER:
 165           /* Allow the code to run the catcher.  */
 166           current_catcher->state = CATCHER_RUNNING;
 167           return 1;
 168         default:
 169           internal_error (__FILE__, __LINE__, "bad state");
 170         }
 171     case CATCHER_RUNNING:
 172       switch (action)
 173         {
 174         case CATCH_ITER:
 175           /* No error/quit has occured.  Just clean up.  */
 176           catcher_pop ();
 177           return 0;
 178         case CATCH_ITER_1:
 179           current_catcher->state = CATCHER_RUNNING_1;
 180           return 1;
 181         case CATCH_THROWING:
 182           current_catcher->state = CATCHER_ABORTING;
 183           /* See also throw_exception.  */
 184           return 1;
 185         default:
 186           internal_error (__FILE__, __LINE__, "bad switch");
 187         }
 188     case CATCHER_RUNNING_1:
 189       switch (action)
 190         {
 191         case CATCH_ITER:
 192           /* The did a "break" from the inner while loop.  */
 193           catcher_pop ();
 194           return 0;
 195         case CATCH_ITER_1:
 196           current_catcher->state = CATCHER_RUNNING;
 197           return 0;
 198         case CATCH_THROWING:
 199           current_catcher->state = CATCHER_ABORTING;
 200           /* See also throw_exception.  */
 201           return 1;
 202         default:
 203           internal_error (__FILE__, __LINE__, "bad switch");
 204         }
 205     case CATCHER_ABORTING:
 206       switch (action)
 207         {
 208         case CATCH_ITER:
 209           {
 210             struct exception exception = *current_catcher->exception;
 211             if (current_catcher->mask & RETURN_MASK (exception.reason))
 212               {
 213                 /* Exit normally if this catcher can handle this
 214                    exception.  The caller analyses the func return
 215                    values.  */
 216                 catcher_pop ();
 217                 return 0;
 218               }
 219             /* The caller didn't request that the event be caught,
 220                relay the event to the next containing
 221                catch_errors(). */
 222             catcher_pop ();
 223             throw_exception (exception);
 224           }
 225         default:
 226           internal_error (__FILE__, __LINE__, "bad state");
 227         }
 228     default:
 229       internal_error (__FILE__, __LINE__, "bad switch");
 230     }
 231 }
 232
 233 /* Return EXCEPTION to the nearest containing catch_errors().  */
 234
 235 NORETURN void
 236 throw_exception (struct exception exception)
 237 {
 238   quit_flag = 0;
 239   immediate_quit = 0;
 240
 241   /* Perhaps it would be cleaner to do this via the cleanup chain (not sure
 242      I can think of a reason why that is vital, though).  */
 243   bpstat_clear_actions (stop_bpstat);   /* Clear queued breakpoint commands */
 244
 245   disable_current_display ();
 246   do_cleanups (ALL_CLEANUPS);
 247   if (target_can_async_p () && !target_executing)
 248     do_exec_cleanups (ALL_CLEANUPS);
 249   if (sync_execution)
 250     do_exec_error_cleanups (ALL_CLEANUPS);
 251
 252   if (annotation_level > 1)
 253     switch (exception.reason)
 254       {
 255       case RETURN_QUIT:
 256         annotate_quit ();
 257         break;
 258       case RETURN_ERROR:
 259         /* Assume that these are all errors.  */
 260         annotate_error ();
 261         break;
 262       default:
 263         internal_error (__FILE__, __LINE__, "Bad switch.");
 264       }
 265
 266   /* Jump to the containing catch_errors() call, communicating REASON
 267      to that call via setjmp's return value.  Note that REASON can't
 268      be zero, by definition in defs.h. */
 269   catcher_state_machine (CATCH_THROWING);
 270   *current_catcher->exception = exception;
 271   SIGLONGJMP (current_catcher->buf, exception.reason);
 272 }
 273
 274 static char *last_message;
 275
 276 NORETURN void
 277 throw_reason (enum return_reason reason)
 278 {
 279   struct exception exception;
 280   memset (&exception, 0, sizeof exception);
 281
 282   exception.reason = reason;
 283   switch (reason)
 284     {
 285     case RETURN_QUIT:
 286       break;
 287     case RETURN_ERROR:
 288       exception.error = GENERIC_ERROR;
 289       exception.message = last_message;
 290       break;
 291     default:
 292       internal_error (__FILE__, __LINE__, "bad switch");
 293     }
 294
 295   throw_exception (exception);
 296 }
 297
 298 static void
 299 do_write (void *data, const char *buffer, long length_buffer)
 300 {
 301   ui_file_write (data, buffer, length_buffer);
 302 }
 303
 304
 305 void
 306 exception_print (struct ui_file *file, const char *pre_print,
 307                  struct exception e)
 308 {
 309   if (e.reason < 0 && e.message != NULL)
 310     {
 311       target_terminal_ours ();
 312       wrap_here ("");           /* Force out any buffered output */
 313       gdb_flush (file);
 314       annotate_error_begin ();
 315       if (pre_print)
 316         fputs_filtered (pre_print, file);
 317
 318       /* KLUGE: cagney/2005-01-13: Write the string out one line at a
 319          time as that way the MI's behavior is preserved.  */
 320       {
 321         const char *start;
 322         const char *end;
 323         for (start = e.message; start != NULL; start = end)
 324           {
 325             end = strchr (start, '\n');
 326             if (end == NULL)
 327               fputs_filtered (start, file);
 328             else
 329               {
 330                 end++;
 331                 ui_file_write (file, start, end - start);
 332               }
 333           }
 334       }
 335       fprintf_filtered (file, "\n");
 336     }
 337 }
 338
 339 NORETURN static void
 340 print_and_throw (enum return_reason reason, enum errors error,
 341                  const char *prefix, const char *fmt,
 342                  va_list ap) ATTR_NORETURN;
 343 NORETURN static void
 344 print_and_throw (enum return_reason reason, enum errors error,
 345                  const char *prefix, const char *fmt, va_list ap)
 346 {
 347   /* FIXME: cagney/2005-01-13: While xstrvprintf is simpler it alters
 348      GDB's output.  Instead of the message being printed
 349      line-at-a-time the message comes out all at once.  The problem is
 350      that the MI testsuite is checks for line-at-a-time messages and
 351      changing this behavior means updating the testsuite.  */
 352
 353   struct exception e;
 354   struct ui_file *tmp_stream;
 355   long len;
 356
 357   /* Convert the message into a print stream.  */
 358   tmp_stream = mem_fileopen ();
 359   make_cleanup_ui_file_delete (tmp_stream);
 360   vfprintf_unfiltered (tmp_stream, fmt, ap);
 361
 362   /* Save the message.  */
 363   xfree (last_message);
 364   last_message = ui_file_xstrdup (tmp_stream, &len);
 365
 366   /* Print the mesage to stderr, but only if the catcher isn't going
 367      to handle/print it locally.  */
 368   if (current_catcher->print_message)
 369     {
 370       if (deprecated_error_begin_hook)
 371         deprecated_error_begin_hook ();
 372
 373       /* Write the message plus any pre_print to gdb_stderr.  */
 374       target_terminal_ours ();
 375       wrap_here ("");           /* Force out any buffered output */
 376       gdb_flush (gdb_stdout);
 377       annotate_error_begin ();
 378       if (error_pre_print)
 379         fputs_filtered (error_pre_print, gdb_stderr);
 380       ui_file_put (tmp_stream, do_write, gdb_stderr);
 381       fprintf_filtered (gdb_stderr, "\n");
 382     }
 383
 384   /* Throw the exception.  */
 385   e.reason = reason;
 386   e.error = error;
 387   e.message = last_message;
 388   throw_exception (e);
 389 }
 390
 391 NORETURN void
 392 throw_verror (enum errors error, const char *fmt, va_list ap)
 393 {
 394   print_and_throw (RETURN_ERROR, error, error_pre_print, fmt, ap);
 395 }
 396
 397 NORETURN void
 398 throw_vfatal (const char *fmt, va_list ap)
 399 {
 400   print_and_throw (RETURN_QUIT, NO_ERROR, quit_pre_print, fmt, ap);
 401 }
 402
 403 NORETURN void
 404 throw_error (enum errors error, const char *fmt, ...)
 405 {
 406   va_list args;
 407   va_start (args, fmt);
 408   print_and_throw (RETURN_ERROR, error, error_pre_print, fmt, args);
 409   va_end (args);
 410 }
 411
 412 /* Call FUNC() with args FUNC_UIOUT and FUNC_ARGS, catching any
 413    errors.  Set FUNC_CAUGHT to an ``enum return_reason'' if the
 414    function is aborted (using throw_exception() or zero if the
 415    function returns normally.  Set FUNC_VAL to the value returned by
 416    the function or 0 if the function was aborted.
 417
 418    Must not be called with immediate_quit in effect (bad things might
 419    happen, say we got a signal in the middle of a memcpy to quit_return).
 420    This is an OK restriction; with very few exceptions immediate_quit can
 421    be replaced by judicious use of QUIT.
 422
 423    MASK specifies what to catch; it is normally set to
 424    RETURN_MASK_ALL, if for no other reason than that the code which
 425    calls catch_errors might not be set up to deal with a quit which
 426    isn't caught.  But if the code can deal with it, it generally
 427    should be RETURN_MASK_ERROR, unless for some reason it is more
 428    useful to abort only the portion of the operation inside the
 429    catch_errors.  Note that quit should return to the command line
 430    fairly quickly, even if some further processing is being done.  */
 431
 432 /* MAYBE: cagney/1999-11-05: catch_errors() in conjunction with
 433    error() et.al. could maintain a set of flags that indicate the the
 434    current state of each of the longjmp buffers.  This would give the
 435    longjmp code the chance to detect a longjmp botch (before it gets
 436    to longjmperror()).  Prior to 1999-11-05 this wasn't possible as
 437    code also randomly used a SET_TOP_LEVEL macro that directly
 438    initialize the longjmp buffers. */
 439
 440 /* MAYBE: cagney/1999-11-05: Should the catch_errors and cleanups code
 441    be consolidated into a single file instead of being distributed
 442    between utils.c and top.c? */
 443
 444 int
 445 catch_exceptions (struct ui_out *uiout,
 446                   catch_exceptions_ftype *func,
 447                   void *func_args,
 448                   char *errstring,
 449                   return_mask mask)
 450 {
 451   return catch_exceptions_with_msg (uiout, func, func_args, errstring,
 452                                     NULL, mask);
 453 }
 454
 455 struct exception
 456 catch_exception (struct ui_out *uiout,
 457                  catch_exception_ftype *func,
 458                  void *func_args,
 459                  return_mask mask)
 460 {
 461   volatile struct exception exception;
 462   SIGJMP_BUF *catch;
 463   catch = catcher_init (uiout, NULL, &exception, mask, 0);
 464   for (SIGSETJMP ((*catch));
 465        catcher_state_machine (CATCH_ITER);)
 466     (*func) (uiout, func_args);
 467   return exception;
 468 }
 469
 470 int
 471 catch_exceptions_with_msg (struct ui_out *uiout,
 472                            catch_exceptions_ftype *func,
 473                            void *func_args,
 474                            char *errstring,
 475                            char **gdberrmsg,
 476                            return_mask mask)
 477 {
 478   volatile struct exception exception;
 479   volatile int val = 0;
 480   SIGJMP_BUF *catch = catcher_init (uiout, errstring, &exception, mask, 1);
 481   for (SIGSETJMP ((*catch)); catcher_state_machine (CATCH_ITER);)
 482     val = (*func) (uiout, func_args);
 483   gdb_assert (val >= 0);
 484   gdb_assert (exception.reason <= 0);
 485   if (exception.reason < 0)
 486     {
 487       /* If caller wants a copy of the low-level error message, make
 488          one.  This is used in the case of a silent error whereby the
 489          caller may optionally want to issue the message.  */
 490       if (gdberrmsg != NULL)
 491         {
 492           if (exception.message != NULL)
 493             *gdberrmsg = xstrdup (exception.message);
 494           else
 495             *gdberrmsg = NULL;
 496         }
 497       return exception.reason;
 498     }
 499   return val;
 500 }
 501
 502 int
 503 catch_errors (catch_errors_ftype *func, void *func_args, char *errstring,
 504               return_mask mask)
 505 {
 506   volatile int val = 0;
 507   volatile struct exception exception;
 508   SIGJMP_BUF *catch = catcher_init (uiout, errstring, &exception, mask, 1);
 509   /* This illustrates how it is possible to nest the mechanism and
 510      hence catch "break".  Of course this doesn't address the need to
 511      also catch "return".  */
 512   for (SIGSETJMP ((*catch)); catcher_state_machine (CATCH_ITER);)
 513     val = func (func_args);
 514   if (exception.reason != 0)
 515     return 0;
 516   return val;
 517 }
 518
 519 struct captured_command_args
 520   {
 521     catch_command_errors_ftype *command;
 522     char *arg;
 523     int from_tty;
 524   };
 525
 526 static int
 527 do_captured_command (void *data)
 528 {
 529   struct captured_command_args *context = data;
 530   context->command (context->arg, context->from_tty);
 531   /* FIXME: cagney/1999-11-07: Technically this do_cleanups() call
 532      isn't needed.  Instead an assertion check could be made that
 533      simply confirmed that the called function correctly cleaned up
 534      after itself.  Unfortunately, old code (prior to 1999-11-04) in
 535      main.c was calling SET_TOP_LEVEL(), calling the command function,
 536      and then *always* calling do_cleanups().  For the moment we
 537      remain ``bug compatible'' with that old code..  */
 538   do_cleanups (ALL_CLEANUPS);
 539   return 1;
 540 }
 541
 542 int
 543 catch_command_errors (catch_command_errors_ftype * command,
 544                       char *arg, int from_tty, return_mask mask)
 545 {
 546   struct captured_command_args args;
 547   args.command = command;
 548   args.arg = arg;
 549   args.from_tty = from_tty;
 550   return catch_errors (do_captured_command, &args, "", mask);
 551 }