gdb/exceptions.c

   1 /* Exception (throw catch) mechanism, for GDB, the GNU debugger.
   2
   3    Copyright (C) 1986-2016 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   immediate_quit = 0;
  34 }
  35
  36 static void
  37 print_flush (void)
  38 {
  39   struct serial *gdb_stdout_serial;
  40
  41   if (deprecated_error_begin_hook)
  42     deprecated_error_begin_hook ();
  43
  44   if (target_supports_terminal_ours ())
  45     target_terminal_ours ();
  46
  47   /* We want all output to appear now, before we print the error.  We
  48      have 3 levels of buffering we have to flush (it's possible that
  49      some of these should be changed to flush the lower-level ones
  50      too):  */
  51
  52   /* 1.  The _filtered buffer.  */
  53   if (filtered_printing_initialized ())
  54     wrap_here ("");
  55
  56   /* 2.  The stdio buffer.  */
  57   gdb_flush (gdb_stdout);
  58   gdb_flush (gdb_stderr);
  59
  60   /* 3.  The system-level buffer.  */
  61   gdb_stdout_serial = serial_fdopen (1);
  62   if (gdb_stdout_serial)
  63     {
  64       serial_drain_output (gdb_stdout_serial);
  65       serial_un_fdopen (gdb_stdout_serial);
  66     }
  67
  68   annotate_error_begin ();
  69 }
  70
  71 static void
  72 print_exception (struct ui_file *file, struct gdb_exception e)
  73 {
  74   /* KLUGE: cagney/2005-01-13: Write the string out one line at a time
  75      as that way the MI's behavior is preserved.  */
  76   const char *start;
  77   const char *end;
  78
  79   for (start = e.message; start != NULL; start = end)
  80     {
  81       end = strchr (start, '\n');
  82       if (end == NULL)
  83         fputs_filtered (start, file);
  84       else
  85         {
  86           end++;
  87           ui_file_write (file, start, end - start);
  88         }
  89     }
  90   fprintf_filtered (file, "\n");
  91
  92   /* Now append the annotation.  */
  93   switch (e.reason)
  94     {
  95     case RETURN_QUIT:
  96       annotate_quit ();
  97       break;
  98     case RETURN_ERROR:
  99       /* Assume that these are all errors.  */
 100       annotate_error ();
 101       break;
 102     default:
 103       internal_error (__FILE__, __LINE__, _("Bad switch."));
 104     }
 105 }
 106
 107 void
 108 exception_print (struct ui_file *file, struct gdb_exception e)
 109 {
 110   if (e.reason < 0 && e.message != NULL)
 111     {
 112       print_flush ();
 113       print_exception (file, e);
 114     }
 115 }
 116
 117 void
 118 exception_fprintf (struct ui_file *file, struct gdb_exception e,
 119                    const char *prefix, ...)
 120 {
 121   if (e.reason < 0 && e.message != NULL)
 122     {
 123       va_list args;
 124
 125       print_flush ();
 126
 127       /* Print the prefix.  */
 128       va_start (args, prefix);
 129       vfprintf_filtered (file, prefix, args);
 130       va_end (args);
 131
 132       print_exception (file, e);
 133     }
 134 }
 135
 136 /* Call FUNC(UIOUT, FUNC_ARGS) but wrapped within an exception
 137    handler.  If an exception (enum return_reason) is thrown using
 138    throw_exception() than all cleanups installed since
 139    catch_exceptions() was entered are invoked, the (-ve) exception
 140    value is then returned by catch_exceptions.  If FUNC() returns
 141    normally (with a positive or zero return value) then that value is
 142    returned by catch_exceptions().  It is an internal_error() for
 143    FUNC() to return a negative value.
 144
 145    See exceptions.h for further usage details.
 146
 147    Must not be called with immediate_quit in effect (bad things might
 148    happen, say we got a signal in the middle of a memcpy to quit_return).
 149    This is an OK restriction; with very few exceptions immediate_quit can
 150    be replaced by judicious use of QUIT.  */
 151
 152 /* MAYBE: cagney/1999-11-05: catch_errors() in conjunction with
 153    error() et al. could maintain a set of flags that indicate the
 154    current state of each of the longjmp buffers.  This would give the
 155    longjmp code the chance to detect a longjmp botch (before it gets
 156    to longjmperror()).  Prior to 1999-11-05 this wasn't possible as
 157    code also randomly used a SET_TOP_LEVEL macro that directly
 158    initialized the longjmp buffers.  */
 159
 160 int
 161 catch_exceptions (struct ui_out *uiout,
 162                   catch_exceptions_ftype *func,
 163                   void *func_args,
 164                   return_mask mask)
 165 {
 166   return catch_exceptions_with_msg (uiout, func, func_args, NULL, mask);
 167 }
 168
 169 int
 170 catch_exceptions_with_msg (struct ui_out *func_uiout,
 171                            catch_exceptions_ftype *func,
 172                            void *func_args,
 173                            char **gdberrmsg,
 174                            return_mask mask)
 175 {
 176   struct gdb_exception exception = exception_none;
 177   volatile int val = 0;
 178   struct ui_out *saved_uiout;
 179
 180   /* Save and override the global ``struct ui_out'' builder.  */
 181   saved_uiout = current_uiout;
 182   current_uiout = func_uiout;
 183
 184   TRY
 185     {
 186       val = (*func) (current_uiout, func_args);
 187     }
 188   CATCH (ex, RETURN_MASK_ALL)
 189     {
 190       exception = ex;
 191     }
 192   END_CATCH
 193
 194   /* Restore the global builder.  */
 195   current_uiout = saved_uiout;
 196
 197   if (exception.reason < 0 && (mask & RETURN_MASK (exception.reason)) == 0)
 198     {
 199       /* The caller didn't request that the event be caught.
 200          Rethrow.  */
 201       throw_exception (exception);
 202     }
 203
 204   exception_print (gdb_stderr, exception);
 205   gdb_assert (val >= 0);
 206   gdb_assert (exception.reason <= 0);
 207   if (exception.reason < 0)
 208     {
 209       /* If caller wants a copy of the low-level error message, make
 210          one.  This is used in the case of a silent error whereby the
 211          caller may optionally want to issue the message.  */
 212       if (gdberrmsg != NULL)
 213         {
 214           if (exception.message != NULL)
 215             *gdberrmsg = xstrdup (exception.message);
 216           else
 217             *gdberrmsg = NULL;
 218         }
 219       return exception.reason;
 220     }
 221   return val;
 222 }
 223
 224 /* This function is superseded by catch_exceptions().  */
 225
 226 int
 227 catch_errors (catch_errors_ftype *func, void *func_args, char *errstring,
 228               return_mask mask)
 229 {
 230   struct gdb_exception exception = exception_none;
 231   volatile int val = 0;
 232   struct ui_out *saved_uiout;
 233
 234   /* Save the global ``struct ui_out'' builder.  */
 235   saved_uiout = current_uiout;
 236
 237   TRY
 238     {
 239       val = func (func_args);
 240     }
 241   CATCH (ex, RETURN_MASK_ALL)
 242     {
 243       exception = ex;
 244     }
 245   END_CATCH
 246
 247   /* Restore the global builder.  */
 248   current_uiout = saved_uiout;
 249
 250   if (exception.reason < 0 && (mask & RETURN_MASK (exception.reason)) == 0)
 251     {
 252       /* The caller didn't request that the event be caught.
 253          Rethrow.  */
 254       throw_exception (exception);
 255     }
 256
 257   exception_fprintf (gdb_stderr, exception, "%s", errstring);
 258   if (exception.reason != 0)
 259     return 0;
 260   return val;
 261 }