gdb/common/common-exceptions.h

   1 /* Exception (throw catch) mechanism, for GDB, the GNU debugger.
   2
   3    Copyright (C) 1986-2019 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_COMMON_EXCEPTIONS_H
  21 #define COMMON_COMMON_EXCEPTIONS_H
  22
  23 #include <setjmp.h>
  24 #include <new>
  25 #include <memory>
  26
  27 /* Reasons for calling throw_exceptions().  NOTE: all reason values
  28    must be different from zero.  enum value 0 is reserved for internal
  29    use as the return value from an initial setjmp().  */
  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_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   gdb_exception ()
 115     : reason ((enum return_reason) 0),
 116       error (GDB_NO_ERROR)
 117   {
 118   }
 119
 120   gdb_exception (enum return_reason r, enum errors e)
 121     : reason (r),
 122       error (e)
 123   {
 124   }
 125
 126   /* The copy constructor exists so that we can mark it "noexcept",
 127      which is a good practice for any sort of exception object.  */
 128   gdb_exception (const gdb_exception &other) noexcept
 129     : reason (other.reason),
 130       error (other.error),
 131       message (other.message)
 132   {
 133   }
 134
 135   /* The assignment operator exists so that we can mark it "noexcept",
 136      which is a good practice for any sort of exception object.  */
 137   gdb_exception &operator= (const gdb_exception &other) noexcept
 138   {
 139     reason = other.reason;
 140     error = other.error;
 141     message = other.message;
 142     return *this;
 143   }
 144
 145   /* Return the contents of the exception message, as a C string.  The
 146      string remains owned by the exception object.  */
 147   const char *what () const noexcept
 148   {
 149     return message->c_str ();
 150   }
 151
 152   enum return_reason reason;
 153   enum errors error;
 154   std::shared_ptr<std::string> message;
 155 };
 156
 157 /* Functions to drive the sjlj-based exceptions state machine.  Though
 158    declared here by necessity, these functions should be considered
 159    internal to the exceptions subsystem and not used other than via
 160    the TRY/CATCH (or TRY_SJLJ/CATCH_SJLJ) macros defined below.  */
 161
 162 extern jmp_buf *exceptions_state_mc_init (void);
 163 extern int exceptions_state_mc_action_iter (void);
 164 extern int exceptions_state_mc_action_iter_1 (void);
 165 extern int exceptions_state_mc_catch (struct gdb_exception *, int);
 166
 167 /* For the C++ try/catch-based TRY/CATCH mechanism.  */
 168
 169 extern void exception_rethrow (void) ATTRIBUTE_NORETURN;
 170
 171 /* Macro to wrap up standard try/catch behavior.
 172
 173    The double loop lets us correctly handle code "break"ing out of the
 174    try catch block.  (It works as the "break" only exits the inner
 175    "while" loop, the outer for loop detects this handling it
 176    correctly.)  Of course "return" and "goto" are not so lucky.
 177
 178    For instance:
 179
 180    *INDENT-OFF*
 181
 182    TRY
 183      {
 184      }
 185    CATCH (e, RETURN_MASK_ERROR)
 186      {
 187        switch (e.reason)
 188          {
 189            case RETURN_ERROR: ...
 190          }
 191      }
 192    END_CATCH
 193
 194   Note that the SJLJ version of the macros are actually named
 195   TRY_SJLJ/CATCH_SJLJ in order to make it possible to call them even
 196   when TRY/CATCH are mapped to C++ try/catch.  The SJLJ variants are
 197   needed in some cases where gdb exceptions need to cross third-party
 198   library code compiled without exceptions support (e.g.,
 199   readline).  */
 200
 201 #define TRY_SJLJ \
 202      { \
 203        jmp_buf *buf = \
 204          exceptions_state_mc_init (); \
 205        setjmp (*buf); \
 206      } \
 207      while (exceptions_state_mc_action_iter ()) \
 208        while (exceptions_state_mc_action_iter_1 ())
 209
 210 #define CATCH_SJLJ(EXCEPTION, MASK)                             \
 211   {                                                     \
 212     struct gdb_exception EXCEPTION;                             \
 213     if (exceptions_state_mc_catch (&(EXCEPTION), MASK))
 214
 215 #define END_CATCH_SJLJ                          \
 216   }
 217
 218 /* We still need to wrap TRY/CATCH in C++ so that cleanups and C++
 219    exceptions can coexist.
 220
 221    The TRY blocked is wrapped in a do/while(0) so that break/continue
 222    within the block works the same as in C.
 223
 224    END_CATCH makes sure that even if the CATCH block doesn't want to
 225    catch the exception, we stop at every frame in the unwind chain to
 226    run its cleanups, which may e.g., have pointers to stack variables
 227    that are going to be destroyed.
 228
 229    There's an outer scope around the whole TRY/END_CATCH in order to
 230    cause a compilation error if you forget to add the END_CATCH at the
 231    end a TRY/CATCH construct.  */
 232
 233 #define TRY                                                             \
 234   {                                                                     \
 235     try                                                                 \
 236       {                                                                 \
 237         do                                                              \
 238           {
 239
 240 #define CATCH(EXCEPTION, MASK)                                          \
 241           } while (0);                                                  \
 242         }                                                               \
 243     catch (struct gdb_exception ## _ ## MASK &EXCEPTION)
 244
 245 #define END_CATCH                               \
 246     catch (...)                                 \
 247       {                                         \
 248         exception_rethrow ();                   \
 249       }                                         \
 250   }
 251
 252 /* The exception types client code may catch.  They're just shims
 253    around gdb_exception that add nothing but type info.  Which is used
 254    is selected depending on the MASK argument passed to CATCH.  */
 255
 256 struct gdb_exception_error : public gdb_exception
 257 {
 258   explicit gdb_exception_error (const gdb_exception &ex) noexcept
 259     : gdb_exception (ex)
 260   {
 261   }
 262 };
 263
 264 struct gdb_exception_quit : public gdb_exception
 265 {
 266   explicit gdb_exception_quit (const gdb_exception &ex) noexcept
 267     : gdb_exception (ex)
 268   {
 269   }
 270 };
 271
 272 /* An exception type that inherits from both std::bad_alloc and a gdb
 273    exception.  This is necessary because operator new can only throw
 274    std::bad_alloc, and OTOH, we want exceptions thrown due to memory
 275    allocation error to be caught by all the CATCH/RETURN_MASK_ALL
 276    spread around the codebase.  */
 277
 278 struct gdb_quit_bad_alloc
 279   : public gdb_exception_quit,
 280     public std::bad_alloc
 281 {
 282   explicit gdb_quit_bad_alloc (const gdb_exception &ex) noexcept
 283     : gdb_exception_quit (ex),
 284       std::bad_alloc ()
 285   {
 286   }
 287 };
 288
 289 /* *INDENT-ON* */
 290
 291 /* Throw an exception (as described by "struct gdb_exception"),
 292    landing in the inner most containing exception handler established
 293    using TRY/CATCH.  */
 294 extern void throw_exception (struct gdb_exception exception)
 295      ATTRIBUTE_NORETURN;
 296
 297 /* Throw an exception by executing a LONG JUMP to the inner most
 298    containing exception handler established using TRY_SJLJ.  Necessary
 299    in some cases where we need to throw GDB exceptions across
 300    third-party library code (e.g., readline).  */
 301 extern void throw_exception_sjlj (struct gdb_exception exception)
 302      ATTRIBUTE_NORETURN;
 303
 304 /* Convenience wrappers around throw_exception that throw GDB
 305    errors.  */
 306 extern void throw_verror (enum errors, const char *fmt, va_list ap)
 307      ATTRIBUTE_NORETURN ATTRIBUTE_PRINTF (2, 0);
 308 extern void throw_vquit (const char *fmt, va_list ap)
 309      ATTRIBUTE_NORETURN ATTRIBUTE_PRINTF (1, 0);
 310 extern void throw_error (enum errors error, const char *fmt, ...)
 311      ATTRIBUTE_NORETURN ATTRIBUTE_PRINTF (2, 3);
 312 extern void throw_quit (const char *fmt, ...)
 313      ATTRIBUTE_NORETURN ATTRIBUTE_PRINTF (1, 2);
 314
 315 /* A pre-defined non-exception.  */
 316 extern const struct gdb_exception exception_none;
 317
 318 #endif /* COMMON_COMMON_EXCEPTIONS_H */