gdb/common/common-exceptions.h

   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 #ifndef COMMON_EXCEPTIONS_H
  21 #define COMMON_EXCEPTIONS_H
  22
  23 #include "gdb_setjmp.h"
  24
  25 /* Reasons for calling throw_exceptions().  NOTE: all reason values
  26    must be less than zero.  enum value 0 is reserved for internal use
  27    as the return value from an initial setjmp().  The function
  28    catch_exceptions() reserves values >= 0 as legal results from its
  29    wrapped function.  */
  30
  31 enum return_reason
  32   {
  33     /* User interrupt.  */
  34     RETURN_QUIT = -2,
  35     /* Any other error.  */
  36     RETURN_ERROR
  37   };
  38
  39 #define RETURN_MASK(reason)     (1 << (int)(-reason))
  40
  41 typedef enum
  42 {
  43   RETURN_MASK_QUIT = RETURN_MASK (RETURN_QUIT),
  44   RETURN_MASK_ERROR = RETURN_MASK (RETURN_ERROR),
  45   RETURN_MASK_ALL = (RETURN_MASK_QUIT | RETURN_MASK_ERROR)
  46 } return_mask;
  47
  48 /* Describe all exceptions.  */
  49
  50 enum errors {
  51   GDB_NO_ERROR,
  52
  53   /* Any generic error, the corresponding text is in
  54      exception.message.  */
  55   GENERIC_ERROR,
  56
  57   /* Something requested was not found.  */
  58   NOT_FOUND_ERROR,
  59
  60   /* Thread library lacks support necessary for finding thread local
  61      storage.  */
  62   TLS_NO_LIBRARY_SUPPORT_ERROR,
  63
  64   /* Load module not found while attempting to find thread local storage.  */
  65   TLS_LOAD_MODULE_NOT_FOUND_ERROR,
  66
  67   /* Thread local storage has not been allocated yet.  */
  68   TLS_NOT_ALLOCATED_YET_ERROR,
  69
  70   /* Something else went wrong while attempting to find thread local
  71      storage.  The ``struct gdb_exception'' message field provides
  72      more detail.  */
  73   TLS_GENERIC_ERROR,
  74
  75   /* Problem parsing an XML document.  */
  76   XML_PARSE_ERROR,
  77
  78   /* Error accessing memory.  */
  79   MEMORY_ERROR,
  80
  81   /* Value not available.  E.g., a register was not collected in a
  82      traceframe.  */
  83   NOT_AVAILABLE_ERROR,
  84
  85   /* Value was optimized out.  Note: if the value was a register, this
  86      means the register was not saved in the frame.  */
  87   OPTIMIZED_OUT_ERROR,
  88
  89   /* DW_OP_GNU_entry_value resolving failed.  */
  90   NO_ENTRY_VALUE_ERROR,
  91
  92   /* Target throwing an error has been closed.  Current command should be
  93      aborted as the inferior state is no longer valid.  */
  94   TARGET_CLOSE_ERROR,
  95
  96   /* An undefined command was executed.  */
  97   UNDEFINED_COMMAND_ERROR,
  98
  99   /* Requested feature, method, mechanism, etc. is not supported.  */
 100   NOT_SUPPORTED_ERROR,
 101
 102   /* The number of candidates generated during line completion has
 103      reached the user's specified limit.  This isn't an error, this exception
 104      is used to halt searching for more completions, but for consistency
 105      "_ERROR" is appended to the name.  */
 106   MAX_COMPLETIONS_REACHED_ERROR,
 107
 108   /* Add more errors here.  */
 109   NR_ERRORS
 110 };
 111
 112 struct gdb_exception
 113 {
 114   enum return_reason reason;
 115   enum errors error;
 116   const char *message;
 117 };
 118
 119 /* The different exception mechanisms that TRY/CATCH can map to.  */
 120
 121 /* Make GDB exceptions use setjmp/longjmp behind the scenes.  This is
 122    the only mode supported when GDB is built as a C program.  */
 123 #define GDB_XCPT_SJMP 1
 124
 125 /* Make GDB exceptions use try/catch behind the scenes.  Can't be made
 126    the default until we stop throwing exceptions from signal
 127    handlers.  */
 128 #define GDB_XCPT_TRY 2
 129
 130 /* Specify this mode to build with TRY/CATCH mapped directly to raw
 131    try/catch.  GDB won't work correctly, but building that way catches
 132    code tryin to break/continue out of the try block, along with
 133    spurious code between the TRY and the CATCH block.  */
 134 #define GDB_XCPT_RAW_TRY 3
 135
 136 /* Always use setjmp/longmp, even in C++ mode.  */
 137 #define GDB_XCPT GDB_XCPT_SJMP
 138
 139 /* Functions to drive the exceptions state machine.  Though declared
 140    here by necessity, these functions should be considered internal to
 141    the exceptions subsystem and not used other than via the TRY/CATCH
 142    macros defined below.  */
 143
 144 #if GDB_XCPT == GDB_XCPT_SJMP
 145 extern SIGJMP_BUF *exceptions_state_mc_init (void);
 146 extern int exceptions_state_mc_action_iter (void);
 147 extern int exceptions_state_mc_action_iter_1 (void);
 148 extern int exceptions_state_mc_catch (struct gdb_exception *, int);
 149 #else
 150 extern void *exception_try_scope_entry (void);
 151 extern void exception_try_scope_exit (void *saved_state);
 152 extern void exception_rethrow (void);
 153 #endif
 154
 155 /* Macro to wrap up standard try/catch behavior.
 156
 157    The double loop lets us correctly handle code "break"ing out of the
 158    try catch block.  (It works as the "break" only exits the inner
 159    "while" loop, the outer for loop detects this handling it
 160    correctly.)  Of course "return" and "goto" are not so lucky.
 161
 162    For instance:
 163
 164    *INDENT-OFF*
 165
 166    TRY
 167      {
 168      }
 169    CATCH (e, RETURN_MASK_ERROR)
 170      {
 171        switch (e.reason)
 172          {
 173            case RETURN_ERROR: ...
 174          }
 175      }
 176    END_CATCH
 177
 178   */
 179
 180 #if GDB_XCPT == GDB_XCPT_SJMP
 181
 182 #define TRY \
 183      { \
 184        SIGJMP_BUF *buf = \
 185          exceptions_state_mc_init (); \
 186        SIGSETJMP (*buf); \
 187      } \
 188      while (exceptions_state_mc_action_iter ()) \
 189        while (exceptions_state_mc_action_iter_1 ())
 190
 191 #define CATCH(EXCEPTION, MASK)                          \
 192   {                                                     \
 193     struct gdb_exception EXCEPTION;                             \
 194     if (exceptions_state_mc_catch (&(EXCEPTION), MASK))
 195
 196 #define END_CATCH                               \
 197   }
 198
 199 #endif /* GDB_XCPT_SJMP */
 200
 201 #if GDB_XCPT == GDB_XCPT_TRY || GDB_XCPT == GDB_XCPT_RAW_TRY
 202
 203 /* Prevent error/quit during TRY from calling cleanups established
 204    prior to here.  This pops out the scope in either case of normal
 205    exit or exception exit.  */
 206 struct exception_try_scope
 207 {
 208   exception_try_scope ()
 209   {
 210     saved_state = exception_try_scope_entry ();
 211   }
 212   ~exception_try_scope ()
 213   {
 214     exception_try_scope_exit (saved_state);
 215   }
 216
 217   void *saved_state;
 218 };
 219
 220 #if GDB_XCPT == GDB_XCPT_TRY
 221
 222 /* We still need to wrap TRY/CATCH in C++ so that cleanups and C++
 223    exceptions can coexist.  The TRY blocked is wrapped in a
 224    do/while(0) so that break/continue within the block works the same
 225    as in C.  */
 226 #define TRY                                                             \
 227   try                                                                   \
 228     {                                                                   \
 229       exception_try_scope exception_try_scope_instance;                 \
 230       do                                                                \
 231         {
 232
 233 #define CATCH(EXCEPTION, MASK)                                          \
 234         } while (0);                                                    \
 235     }                                                                   \
 236   catch (struct gdb_exception ## _ ## MASK &EXCEPTION)
 237
 238 #define END_CATCH                               \
 239   catch (...)                                   \
 240   {                                             \
 241     exception_rethrow ();                       \
 242   }
 243
 244 #else
 245
 246 #define TRY try
 247 #define CATCH(EXCEPTION, MASK) \
 248   catch (struct gdb_exception ## _ ## MASK &EXCEPTION)
 249 #define END_CATCH
 250
 251 #endif
 252
 253 /* The exception types client code may catch.  They're just shims
 254    around gdb_exception that add nothing but type info.  Which is used
 255    is selected depending on the MASK argument passed to CATCH.  */
 256
 257 struct gdb_exception_RETURN_MASK_ALL : public gdb_exception
 258 {
 259 };
 260
 261 struct gdb_exception_RETURN_MASK_ERROR : public gdb_exception_RETURN_MASK_ALL
 262 {
 263 };
 264
 265 struct gdb_exception_RETURN_MASK_QUIT : public gdb_exception_RETURN_MASK_ALL
 266 {
 267 };
 268
 269 #endif /* GDB_XCPT_TRY || GDB_XCPT_RAW_TRY */
 270
 271 /* *INDENT-ON* */
 272
 273 /* Hook to allow client-specific actions to be performed prior to
 274    throwing an exception.  This function must be provided by the
 275    client, and will be called before any cleanups are run.  */
 276
 277 extern void prepare_to_throw_exception (void);
 278
 279 /* Throw an exception (as described by "struct gdb_exception").  Will
 280    execute a LONG JUMP to the inner most containing exception handler
 281    established using catch_exceptions() (or similar).
 282
 283    Code normally throws an exception using error() et.al.  For various
 284    reaons, GDB also contains code that throws an exception directly.
 285    For instance, the remote*.c targets contain CNTRL-C signal handlers
 286    that propogate the QUIT event up the exception chain.  ``This could
 287    be a good thing or a dangerous thing.'' -- the Existential
 288    Wombat.  */
 289
 290 extern void throw_exception (struct gdb_exception exception)
 291      ATTRIBUTE_NORETURN;
 292 extern void throw_verror (enum errors, const char *fmt, va_list ap)
 293      ATTRIBUTE_NORETURN ATTRIBUTE_PRINTF (2, 0);
 294 extern void throw_vquit (const char *fmt, va_list ap)
 295      ATTRIBUTE_NORETURN ATTRIBUTE_PRINTF (1, 0);
 296 extern void throw_error (enum errors error, const char *fmt, ...)
 297      ATTRIBUTE_NORETURN ATTRIBUTE_PRINTF (2, 3);
 298 extern void throw_quit (const char *fmt, ...)
 299      ATTRIBUTE_NORETURN ATTRIBUTE_PRINTF (1, 2);
 300
 301 /* A pre-defined non-exception.  */
 302 extern const struct gdb_exception exception_none;
 303
 304 #endif /* COMMON_EXCEPTIONS_H */