gdb/exceptions.c

   1 /* Exception (throw catch) mechanism, for GDB, the GNU debugger.
   2
   3    Copyright (C) 1986-2015 Free Software Foundation, Inc.
   4
   5    This file is part of GDB.
   6
   7    This program 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 3 of the License, or
  10    (at your option) any later version.
  11
  12    This program 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 this program.  If not, see <http://www.gnu.org/licenses/>.  */
  19
  20 #include "defs.h"
  21 #include "exceptions.h"
  22 #include "breakpoint.h"
  23 #include "target.h"
  24 #include "inferior.h"
  25 #include "annotate.h"
  26 #include "ui-out.h"
  27 #include "serial.h"
  28 #include "gdbthread.h"
  29
  30 void
  31 prepare_to_throw_exception (void)
  32 {
  33   clear_quit_flag ();
  34   immediate_quit = 0;
  35 }
  36
  37 static void
  38 print_flush (void)
  39 {
  40   struct serial *gdb_stdout_serial;
  41
  42   if (deprecated_error_begin_hook)
  43     deprecated_error_begin_hook ();
  44
  45   if (target_supports_terminal_ours ())
  46     target_terminal_ours ();
  47
  48   /* We want all output to appear now, before we print the error.  We
  49      have 3 levels of buffering we have to flush (it's possible that
  50      some of these should be changed to flush the lower-level ones
  51      too):  */
  52
  53   /* 1.  The _filtered buffer.  */
  54   if (filtered_printing_initialized ())
  55     wrap_here ("");
  56
  57   /* 2.  The stdio buffer.  */
  58   gdb_flush (gdb_stdout);
  59   gdb_flush (gdb_stderr);
  60
  61   /* 3.  The system-level buffer.  */
  62   gdb_stdout_serial = serial_fdopen (1);
  63   if (gdb_stdout_serial)
  64     {
  65       serial_drain_output (gdb_stdout_serial);
  66       serial_un_fdopen (gdb_stdout_serial);
  67     }
  68
  69   annotate_error_begin ();
  70 }
  71
  72 static void
  73 print_exception (struct ui_file *file, struct gdb_exception e)
  74 {
  75   /* KLUGE: cagney/2005-01-13: Write the string out one line at a time
  76      as that way the MI's behavior is preserved.  */
  77   const char *start;
  78   const char *end;
  79
  80   for (start = e.message; start != NULL; start = end)
  81     {
  82       end = strchr (start, '\n');
  83       if (end == NULL)
  84         fputs_filtered (start, file);
  85       else
  86         {
  87           end++;
  88           ui_file_write (file, start, end - start);
  89         }
  90     }
  91   fprintf_filtered (file, "\n");
  92
  93   /* Now append the annotation.  */
  94   switch (e.reason)
  95     {
  96     case RETURN_QUIT:
  97       annotate_quit ();
  98       break;
  99     case RETURN_ERROR:
 100       /* Assume that these are all errors.  */
 101       annotate_error ();
 102       break;
 103     default:
 104       internal_error (__FILE__, __LINE__, _("Bad switch."));
 105     }
 106 }
 107
 108 void
 109 exception_print (struct ui_file *file, struct gdb_exception e)
 110 {
 111   if (e.reason < 0 && e.message != NULL)
 112     {
 113       print_flush ();
 114       print_exception (file, e);
 115     }
 116 }
 117
 118 void
 119 exception_fprintf (struct ui_file *file, struct gdb_exception e,
 120                    const char *prefix, ...)
 121 {
 122   if (e.reason < 0 && e.message != NULL)
 123     {
 124       va_list args;
 125
 126       print_flush ();
 127
 128       /* Print the prefix.  */
 129       va_start (args, prefix);
 130       vfprintf_filtered (file, prefix, args);
 131       va_end (args);
 132
 133       print_exception (file, e);
 134     }
 135 }
 136
 137 /* Call FUNC(UIOUT, FUNC_ARGS) but wrapped within an exception
 138    handler.  If an exception (enum return_reason) is thrown using
 139    throw_exception() than all cleanups installed since
 140    catch_exceptions() was entered are invoked, the (-ve) exception
 141    value is then returned by catch_exceptions.  If FUNC() returns
 142    normally (with a positive or zero return value) then that value is
 143    returned by catch_exceptions().  It is an internal_error() for
 144    FUNC() to return a negative value.
 145
 146    See exceptions.h for further usage details.
 147
 148    Must not be called with immediate_quit in effect (bad things might
 149    happen, say we got a signal in the middle of a memcpy to quit_return).
 150    This is an OK restriction; with very few exceptions immediate_quit can
 151    be replaced by judicious use of QUIT.  */
 152
 153 /* MAYBE: cagney/1999-11-05: catch_errors() in conjunction with
 154    error() et al. could maintain a set of flags that indicate the
 155    current state of each of the longjmp buffers.  This would give the
 156    longjmp code the chance to detect a longjmp botch (before it gets
 157    to longjmperror()).  Prior to 1999-11-05 this wasn't possible as
 158    code also randomly used a SET_TOP_LEVEL macro that directly
 159    initialized the longjmp buffers.  */
 160
 161 int
 162 catch_exceptions (struct ui_out *uiout,
 163                   catch_exceptions_ftype *func,
 164                   void *func_args,
 165                   return_mask mask)
 166 {
 167   return catch_exceptions_with_msg (uiout, func, func_args, NULL, mask);
 168 }
 169
 170 int
 171 catch_exceptions_with_msg (struct ui_out *func_uiout,
 172                            catch_exceptions_ftype *func,
 173                            void *func_args,
 174                            char **gdberrmsg,
 175                            return_mask mask)
 176 {
 177   struct gdb_exception exception = exception_none;
 178   volatile int val = 0;
 179   struct ui_out *saved_uiout;
 180
 181   /* Save and override the global ``struct ui_out'' builder.  */
 182   saved_uiout = current_uiout;
 183   current_uiout = func_uiout;
 184
 185   TRY
 186     {
 187       val = (*func) (current_uiout, func_args);
 188     }
 189   CATCH (ex, RETURN_MASK_ALL)
 190     {
 191       exception = ex;
 192     }
 193   END_CATCH
 194
 195   /* Restore the global builder.  */
 196   current_uiout = saved_uiout;
 197
 198   if (exception.reason < 0 && (mask & RETURN_MASK (exception.reason)) == 0)
 199     {
 200       /* The caller didn't request that the event be caught.
 201          Rethrow.  */
 202       throw_exception (exception);
 203     }
 204
 205   exception_print (gdb_stderr, exception);
 206   gdb_assert (val >= 0);
 207   gdb_assert (exception.reason <= 0);
 208   if (exception.reason < 0)
 209     {
 210       /* If caller wants a copy of the low-level error message, make
 211          one.  This is used in the case of a silent error whereby the
 212          caller may optionally want to issue the message.  */
 213       if (gdberrmsg != NULL)
 214         {
 215           if (exception.message != NULL)
 216             *gdberrmsg = xstrdup (exception.message);
 217           else
 218             *gdberrmsg = NULL;
 219         }
 220       return exception.reason;
 221     }
 222   return val;
 223 }
 224
 225 /* This function is superseded by catch_exceptions().  */
 226
 227 int
 228 catch_errors (catch_errors_ftype *func, void *func_args, char *errstring,
 229               return_mask mask)
 230 {
 231   struct gdb_exception exception = exception_none;
 232   volatile int val = 0;
 233   struct ui_out *saved_uiout;
 234
 235   /* Save the global ``struct ui_out'' builder.  */
 236   saved_uiout = current_uiout;
 237
 238   TRY
 239     {
 240       val = func (func_args);
 241     }
 242   CATCH (ex, RETURN_MASK_ALL)
 243     {
 244       exception = ex;
 245     }
 246   END_CATCH
 247
 248   /* Restore the global builder.  */
 249   current_uiout = saved_uiout;
 250
 251   if (exception.reason < 0 && (mask & RETURN_MASK (exception.reason)) == 0)
 252     {
 253       /* The caller didn't request that the event be caught.
 254          Rethrow.  */
 255       throw_exception (exception);
 256     }
 257
 258   exception_fprintf (gdb_stderr, exception, "%s", errstring);
 259   if (exception.reason != 0)
 260     return 0;
 261   return val;
 262 }